1635 lines
82 KiB
Plaintext
1635 lines
82 KiB
Plaintext
Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
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Copyright (c) 1991-1996 by Xerox Corporation. All rights reserved.
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Copyright (c) 1996-1999 by Silicon Graphics. All rights reserved.
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Copyright (c) 1999 by Hewlett-Packard Company. All rights reserved.
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[ This version of the collector modified for use in libgcj.
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See the file ChangeLog for details ]
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THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
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OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
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Permission is hereby granted to use or copy this program
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for any purpose, provided the above notices are retained on all copies.
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Permission to modify the code and to distribute modified code is granted,
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provided the above notices are retained, and a notice that the code was
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modified is included with the above copyright notice.
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This is version 5.0 of a conservative garbage collector for C and C++.
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You might find a more recent version of this at
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http://www.hpl.hp.com/personal/Hans_Boehm/gc
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HISTORY -
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Early versions of this collector were developed as a part of research
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projects supported in part by the National Science Foundation
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and the Defense Advance Research Projects Agency.
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Much of the code was rewritten by Hans-J. Boehm (boehm@acm.org) at Xerox PARC,
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SGI, and HP Labs.
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Some other contributors:
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More recent contributors are mentioned in the modification history at the
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end of this file. My apologies for any omissions.
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The SPARC specific code was contributed by Mark Weiser
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(weiser@parc.xerox.com). The Encore Multimax modifications were supplied by
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Kevin Kenny (kenny@m.cs.uiuc.edu). The adaptation to the RT is largely due
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to Vernon Lee (scorpion@rice.edu), on machines made available by IBM.
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Much of the HP specific code and a number of good suggestions for improving the
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generic code are due to Walter Underwood (wunder@hp-ses.sde.hp.com).
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Robert Brazile (brazile@diamond.bbn.com) originally supplied the ULTRIX code.
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Al Dosser (dosser@src.dec.com) and Regis Cridlig (Regis.Cridlig@cl.cam.ac.uk)
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subsequently provided updates and information on variation between ULTRIX
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systems. Parag Patel (parag@netcom.com) supplied the A/UX code.
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Jesper Peterson(jep@mtiame.mtia.oz.au), Michel Schinz, and
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Martin Tauchmann (martintauchmann@bigfoot.com) supplied the Amiga port.
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Thomas Funke (thf@zelator.in-berlin.de(?)) and
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Brian D.Carlstrom (bdc@clark.lcs.mit.edu) supplied the NeXT ports.
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Douglas Steel (doug@wg.icl.co.uk) provided ICL DRS6000 code.
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Bill Janssen (janssen@parc.xerox.com) supplied the SunOS dynamic loader
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specific code. Manuel Serrano (serrano@cornas.inria.fr) supplied linux and
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Sony News specific code. Al Dosser provided Alpha/OSF/1 code. He and
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Dave Detlefs(detlefs@src.dec.com) also provided several generic bug fixes.
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Alistair G. Crooks(agc@uts.amdahl.com) supplied the NetBSD and 386BSD ports.
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Jeffrey Hsu (hsu@soda.berkeley.edu) provided the FreeBSD port.
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Brent Benson (brent@jade.ssd.csd.harris.com) ported the collector to
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a Motorola 88K processor running CX/UX (Harris NightHawk).
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Ari Huttunen (Ari.Huttunen@hut.fi) generalized the OS/2 port to
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nonIBM development environments (a nontrivial task).
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Patrick Beard (beard@cs.ucdavis.edu) provided the initial MacOS port.
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David Chase, then at Olivetti Research, suggested several improvements.
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Scott Schwartz (schwartz@groucho.cse.psu.edu) supplied some of the
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code to save and print call stacks for leak detection on a SPARC.
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Jesse Hull and John Ellis supplied the C++ interface code.
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Zhong Shao performed much of the experimentation that led to the
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current typed allocation facility. (His dynamic type inference code hasn't
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made it into the released version of the collector, yet.)
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(Blame for misinstallation of these modifications goes to the first author,
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however.)
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OVERVIEW
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This is intended to be a general purpose, garbage collecting storage
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allocator. The algorithms used are described in:
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Boehm, H., and M. Weiser, "Garbage Collection in an Uncooperative Environment",
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Software Practice & Experience, September 1988, pp. 807-820.
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Boehm, H., A. Demers, and S. Shenker, "Mostly Parallel Garbage Collection",
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Proceedings of the ACM SIGPLAN '91 Conference on Programming Language Design
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and Implementation, SIGPLAN Notices 26, 6 (June 1991), pp. 157-164.
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Boehm, H., "Space Efficient Conservative Garbage Collection", Proceedings
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of the ACM SIGPLAN '91 Conference on Programming Language Design and
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Implementation, SIGPLAN Notices 28, 6 (June 1993), pp. 197-206.
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Possible interactions between the collector and optimizing compilers are
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discussed in
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Boehm, H., and D. Chase, "A Proposal for GC-safe C Compilation",
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The Journal of C Language Translation 4, 2 (December 1992).
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and
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Boehm H., "Simple GC-safe Compilation", Proceedings
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of the ACM SIGPLAN '96 Conference on Programming Language Design and
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Implementation.
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(Both are also available from
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http://reality.sgi.com/boehm/papers/, among other places.)
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Unlike the collector described in the second reference, this collector
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operates either with the mutator stopped during the entire collection
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(default) or incrementally during allocations. (The latter is supported
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on only a few machines.) It does not rely on threads, but is intended
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to be thread-safe.
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Some of the ideas underlying the collector have previously been explored
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by others. (Doug McIlroy wrote a vaguely similar collector that is part of
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version 8 UNIX (tm).) However none of this work appears to have been widely
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disseminated.
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Rudimentary tools for use of the collector as a leak detector are included, as
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is a fairly sophisticated string package "cord" that makes use of the collector.
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(See cord/README.)
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GENERAL DESCRIPTION
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This is a garbage collecting storage allocator that is intended to be
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used as a plug-in replacement for C's malloc.
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Since the collector does not require pointers to be tagged, it does not
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attempt to ensure that all inaccessible storage is reclaimed. However,
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in our experience, it is typically more successful at reclaiming unused
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memory than most C programs using explicit deallocation. Unlike manually
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introduced leaks, the amount of unreclaimed memory typically stays
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bounded.
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In the following, an "object" is defined to be a region of memory allocated
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by the routines described below.
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Any objects not intended to be collected must be pointed to either
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from other such accessible objects, or from the registers,
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stack, data, or statically allocated bss segments. Pointers from
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the stack or registers may point to anywhere inside an object.
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The same is true for heap pointers if the collector is compiled with
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ALL_INTERIOR_POINTERS defined, as is now the default.
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Compiling without ALL_INTERIOR_POINTERS may reduce accidental retention
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of garbage objects, by requiring pointers from the heap to to the beginning
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of an object. But this no longer appears to be a significant
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issue for most programs.
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There are a number of routines which modify the pointer recognition
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algorithm. GC_register_displacement allows certain interior pointers
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to be recognized even if ALL_INTERIOR_POINTERS is nor defined.
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GC_malloc_ignore_off_page allows some pointers into the middle of large objects
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to be disregarded, greatly reducing the probablility of accidental
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retention of large objects. For most purposes it seems best to compile
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with ALL_INTERIOR_POINTERS and to use GC_malloc_ignore_off_page if
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you get collector warnings from allocations of very large objects.
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See README.debugging for details.
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Note that pointers inside memory allocated by the standard "malloc" are not
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seen by the garbage collector. Thus objects pointed to only from such a
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region may be prematurely deallocated. It is thus suggested that the
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standard "malloc" be used only for memory regions, such as I/O buffers, that
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are guaranteed not to contain pointers to garbage collectable memory.
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Pointers in C language automatic, static, or register variables,
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are correctly recognized. (Note that GC_malloc_uncollectable has semantics
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similar to standard malloc, but allocates objects that are traced by the
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collector.)
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The collector does not always know how to find pointers in data
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areas that are associated with dynamic libraries. This is easy to
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remedy IF you know how to find those data areas on your operating
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system (see GC_add_roots). Code for doing this under SunOS, IRIX 5.X and 6.X,
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HP/UX, Alpha OSF/1, Linux, and win32 is included and used by default. (See
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README.win32 for win32 details.) On other systems pointers from dynamic
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library data areas may not be considered by the collector.
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Note that the garbage collector does not need to be informed of shared
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read-only data. However if the shared library mechanism can introduce
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discontiguous data areas that may contain pointers, then the collector does
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need to be informed.
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Signal processing for most signals may be deferred during collection,
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and during uninterruptible parts of the allocation process. Unlike
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standard ANSI C mallocs, it can be safe to invoke malloc
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from a signal handler while another malloc is in progress, provided
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the original malloc is not restarted. (Empirically, many UNIX
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applications already assume this.) To obtain this level of signal
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safety, remove the definition of -DNO_SIGNALS in Makefile. This incurs
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a minor performance penalty, and hence is no longer the default.
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The allocator/collector can also be configured for thread-safe operation.
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(Full signal safety can also be achieved, but only at the cost of two system
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calls per malloc, which is usually unacceptable.)
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INSTALLATION AND PORTABILITY
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As distributed, the macro SILENT is defined in Makefile.
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In the event of problems, this can be removed to obtain a moderate
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amount of descriptive output for each collection.
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(The given statistics exhibit a few peculiarities.
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Things don't appear to add up for a variety of reasons, most notably
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fragmentation losses. These are probably much more significant for the
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contrived program "test.c" than for your application.)
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Note that typing "make test" will automatically build the collector
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and then run setjmp_test and gctest. Setjmp_test will give you information
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about configuring the collector, which is useful primarily if you have
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a machine that's not already supported. Gctest is a somewhat superficial
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test of collector functionality. Failure is indicated by a core dump or
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a message to the effect that the collector is broken. Gctest takes about
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35 seconds to run on a SPARCstation 2. On a slower machine,
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expect it to take a while. It may use up to 8 MB of memory. (The
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multi-threaded version will use more.) "Make test" will also, as
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its last step, attempt to build and test the "cord" string library.
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This will fail without an ANSI C compiler.
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The Makefile will generate a library gc.a which you should link against.
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Typing "make cords" will add the cord library to gc.a.
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Note that this requires an ANSI C compiler.
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It is suggested that if you need to replace a piece of the collector
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(e.g. GC_mark_rts.c) you simply list your version ahead of gc.a on the
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work.)
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ld command line, rather than replacing the one in gc.a. (This will
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generate numerous warnings under some versions of AIX, but it still
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works.)
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All include files that need to be used by clients will be put in the
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include subdirectory. (Normally this is just gc.h. "Make cords" adds
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"cord.h" and "ec.h".)
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The collector currently is designed to run essentially unmodified on
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machines that use a flat 32-bit or 64-bit address space.
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That includes the vast majority of Workstations and X86 (X >= 3) PCs.
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(The list here was deleted because it was getting too long and constantly
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out of date.)
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It does NOT run under plain 16-bit DOS or Windows 3.X. There are however
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various packages (e.g. win32s, djgpp) that allow flat 32-bit address
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applications to run under those systemsif the have at least an 80386 processor,
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and several of those are compatible with the collector.
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In a few cases (Amiga, OS/2, Win32, MacOS) a separate makefile
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or equivalent is supplied. Many of these have separate README.system
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files.
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Dynamic libraries are completely supported only under SunOS
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(and even that support is not functional on the last Sun 3 release),
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IRIX 5&6, HP-PA, Win32 (not Win32S) and OSF/1 on DEC AXP machines.
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On other machines we recommend that you do one of the following:
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1) Add dynamic library support (and send us the code).
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2) Use static versions of the libraries.
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3) Arrange for dynamic libraries to use the standard malloc.
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This is still dangerous if the library stores a pointer to a
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garbage collected object. But nearly all standard interfaces
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prohibit this, because they deal correctly with pointers
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to stack allocated objects. (Strtok is an exception. Don't
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use it.)
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In all cases we assume that pointer alignment is consistent with that
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enforced by the standard C compilers. If you use a nonstandard compiler
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you may have to adjust the alignment parameters defined in gc_priv.h.
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A port to a machine that is not byte addressed, or does not use 32 bit
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or 64 bit addresses will require a major effort. A port to plain MSDOS
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or win16 is hard.
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For machines not already mentioned, or for nonstandard compilers, the
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following are likely to require change:
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1. The parameters in gcconfig.h.
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The parameters that will usually require adjustment are
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STACKBOTTOM, ALIGNMENT and DATASTART. Setjmp_test
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prints its guesses of the first two.
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DATASTART should be an expression for computing the
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address of the beginning of the data segment. This can often be
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&etext. But some memory management units require that there be
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some unmapped space between the text and the data segment. Thus
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it may be more complicated. On UNIX systems, this is rarely
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documented. But the adb "$m" command may be helpful. (Note
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that DATASTART will usually be a function of &etext. Thus a
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single experiment is usually insufficient.)
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STACKBOTTOM is used to initialize GC_stackbottom, which
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should be a sufficient approximation to the coldest stack address.
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On some machines, it is difficult to obtain such a value that is
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valid across a variety of MMUs, OS releases, etc. A number of
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alternatives exist for using the collector in spite of this. See the
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discussion in gcconfig.h immediately preceding the various
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definitions of STACKBOTTOM.
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2. mach_dep.c.
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The most important routine here is one to mark from registers.
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The distributed file includes a generic hack (based on setjmp) that
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happens to work on many machines, and may work on yours. Try
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compiling and running setjmp_t.c to see whether it has a chance of
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working. (This is not correct C, so don't blame your compiler if it
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doesn't work. Based on limited experience, register window machines
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are likely to cause trouble. If your version of setjmp claims that
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all accessible variables, including registers, have the value they
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had at the time of the longjmp, it also will not work. Vanilla 4.2 BSD
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on Vaxen makes such a claim. SunOS does not.)
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If your compiler does not allow in-line assembly code, or if you prefer
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not to use such a facility, mach_dep.c may be replaced by a .s file
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(as we did for the MIPS machine and the PC/RT).
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At this point enough architectures are supported by mach_dep.c
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that you will rarely need to do more than adjust for assembler
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syntax.
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3. os_dep.c (and gc_priv.h).
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Several kinds of operating system dependent routines reside here.
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Many are optional. Several are invoked only through corresponding
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macros in gc_priv.h, which may also be redefined as appropriate.
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The routine GC_register_data_segments is crucial. It registers static
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data areas that must be traversed by the collector. (User calls to
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GC_add_roots may sometimes be used for similar effect.)
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Routines to obtain memory from the OS also reside here.
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Alternatively this can be done entirely by the macro GET_MEM
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defined in gc_priv.h. Routines to disable and reenable signals
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also reside here if they are need by the macros DISABLE_SIGNALS
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and ENABLE_SIGNALS defined in gc_priv.h.
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In a multithreaded environment, the macros LOCK and UNLOCK
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in gc_priv.h will need to be suitably redefined.
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The incremental collector requires page dirty information, which
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is acquired through routines defined in os_dep.c. Unless directed
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otherwise by gcconfig.h, these are implemented as stubs that simply
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treat all pages as dirty. (This of course makes the incremental
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collector much less useful.)
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4. dyn_load.c
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This provides a routine that allows the collector to scan data
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segments associated with dynamic libraries. Often it is not
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necessary to provide this routine unless user-written dynamic
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libraries are used.
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For a different version of UN*X or different machines using the
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Motorola 68000, Vax, SPARC, 80386, NS 32000, PC/RT, or MIPS architecture,
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it should frequently suffice to change definitions in gcconfig.h.
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THE C INTERFACE TO THE ALLOCATOR
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The following routines are intended to be directly called by the user.
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Note that usually only GC_malloc is necessary. GC_clear_roots and GC_add_roots
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calls may be required if the collector has to trace from nonstandard places
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(e.g. from dynamic library data areas on a machine on which the
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collector doesn't already understand them.) On some machines, it may
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be desirable to set GC_stacktop to a good approximation of the stack base.
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(This enhances code portability on HP PA machines, since there is no
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good way for the collector to compute this value.) Client code may include
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"gc.h", which defines all of the following, plus many others.
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1) GC_malloc(nbytes)
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- allocate an object of size nbytes. Unlike malloc, the object is
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cleared before being returned to the user. Gc_malloc will
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invoke the garbage collector when it determines this to be appropriate.
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GC_malloc may return 0 if it is unable to acquire sufficient
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space from the operating system. This is the most probable
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consequence of running out of space. Other possible consequences
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are that a function call will fail due to lack of stack space,
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or that the collector will fail in other ways because it cannot
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maintain its internal data structures, or that a crucial system
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process will fail and take down the machine. Most of these
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possibilities are independent of the malloc implementation.
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2) GC_malloc_atomic(nbytes)
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- allocate an object of size nbytes that is guaranteed not to contain any
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pointers. The returned object is not guaranteed to be cleared.
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(Can always be replaced by GC_malloc, but results in faster collection
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times. The collector will probably run faster if large character
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arrays, etc. are allocated with GC_malloc_atomic than if they are
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statically allocated.)
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3) GC_realloc(object, new_size)
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- change the size of object to be new_size. Returns a pointer to the
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new object, which may, or may not, be the same as the pointer to
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the old object. The new object is taken to be atomic iff the old one
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was. If the new object is composite and larger than the original object,
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then the newly added bytes are cleared (we hope). This is very likely
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to allocate a new object, unless MERGE_SIZES is defined in gc_priv.h.
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Even then, it is likely to recycle the old object only if the object
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is grown in small additive increments (which, we claim, is generally bad
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coding practice.)
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4) GC_free(object)
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- explicitly deallocate an object returned by GC_malloc or
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GC_malloc_atomic. Not necessary, but can be used to minimize
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collections if performance is critical. Probably a performance
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loss for very small objects (<= 8 bytes).
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5) GC_expand_hp(bytes)
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- Explicitly increase the heap size. (This is normally done automatically
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if a garbage collection failed to GC_reclaim enough memory. Explicit
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calls to GC_expand_hp may prevent unnecessarily frequent collections at
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program startup.)
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6) GC_malloc_ignore_off_page(bytes)
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- identical to GC_malloc, but the client promises to keep a pointer to
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the somewhere within the first 256 bytes of the object while it is
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live. (This pointer should nortmally be declared volatile to prevent
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interference from compiler optimizations.) This is the recommended
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way to allocate anything that is likely to be larger than 100Kbytes
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or so. (GC_malloc may result in failure to reclaim such objects.)
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7) GC_set_warn_proc(proc)
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- Can be used to redirect warnings from the collector. Such warnings
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should be rare, and should not be ignored during code development.
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8) GC_enable_incremental()
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- Enables generational and incremental collection. Useful for large
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heaps on machines that provide access to page dirty information.
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Some dirty bit implementations may interfere with debugging
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(by catching address faults) and place restrictions on heap arguments
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to system calls (since write faults inside a system call may not be
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handled well).
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9) Several routines to allow for registration of finalization code.
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User supplied finalization code may be invoked when an object becomes
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unreachable. To call (*f)(obj, x) when obj becomes inaccessible, use
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GC_register_finalizer(obj, f, x, 0, 0);
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For more sophisticated uses, and for finalization ordering issues,
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see gc.h.
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The global variable GC_free_space_divisor may be adjusted up from its
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default value of 4 to use less space and more collection time, or down for
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the opposite effect. Setting it to 1 or 0 will effectively disable collections
|
|
and cause all allocations to simply grow the heap.
|
|
|
|
The variable GC_non_gc_bytes, which is normally 0, may be changed to reflect
|
|
the amount of memory allocated by the above routines that should not be
|
|
considered as a candidate for collection. Careless use may, of course, result
|
|
in excessive memory consumption.
|
|
|
|
Some additional tuning is possible through the parameters defined
|
|
near the top of gc_priv.h.
|
|
|
|
If only GC_malloc is intended to be used, it might be appropriate to define:
|
|
|
|
#define malloc(n) GC_malloc(n)
|
|
#define calloc(m,n) GC_malloc((m)*(n))
|
|
|
|
For small pieces of VERY allocation intensive code, gc_inl.h
|
|
includes some allocation macros that may be used in place of GC_malloc
|
|
and friends.
|
|
|
|
All externally visible names in the garbage collector start with "GC_".
|
|
To avoid name conflicts, client code should avoid this prefix, except when
|
|
accessing garbage collector routines or variables.
|
|
|
|
There are provisions for allocation with explicit type information.
|
|
This is rarely necessary. Details can be found in gc_typed.h.
|
|
|
|
THE C++ INTERFACE TO THE ALLOCATOR:
|
|
|
|
The Ellis-Hull C++ interface to the collector is included in
|
|
the collector distribution. If you intend to use this, type
|
|
"make c++" after the initial build of the collector is complete.
|
|
See gc_cpp.h for the definition of the interface. This interface
|
|
tries to approximate the Ellis-Detlefs C++ garbage collection
|
|
proposal without compiler changes.
|
|
|
|
Cautions:
|
|
1. Arrays allocated without new placement syntax are
|
|
allocated as uncollectable objects. They are traced by the
|
|
collector, but will not be reclaimed.
|
|
|
|
2. Failure to use "make c++" in combination with (1) will
|
|
result in arrays allocated using the default new operator.
|
|
This is likely to result in disaster without linker warnings.
|
|
|
|
3. If your compiler supports an overloaded new[] operator,
|
|
then gc_cpp.cc and gc_cpp.h should be suitably modified.
|
|
|
|
4. Many current C++ compilers have deficiencies that
|
|
break some of the functionality. See the comments in gc_cpp.h
|
|
for suggested workarounds.
|
|
|
|
USE AS LEAK DETECTOR:
|
|
|
|
The collector may be used to track down leaks in C programs that are
|
|
intended to run with malloc/free (e.g. code with extreme real-time or
|
|
portability constraints). To do so define FIND_LEAK in Makefile
|
|
This will cause the collector to invoke the report_leak
|
|
routine defined near the top of reclaim.c whenever an inaccessible
|
|
object is found that has not been explicitly freed. The collector will
|
|
no longer reclaim inaccessible memory; in this form it is purely a
|
|
debugging tool.
|
|
Productive use of this facility normally involves redefining report_leak
|
|
to do something more intelligent. This typically requires annotating
|
|
objects with additional information (e.g. creation time stack trace) that
|
|
identifies their origin. Such code is typically not very portable, and is
|
|
not included here, except on SPARC machines.
|
|
If all objects are allocated with GC_DEBUG_MALLOC (see next section),
|
|
then the default version of report_leak will report the source file
|
|
and line number at which the leaked object was allocated. This may
|
|
sometimes be sufficient. (On SPARC/SUNOS4 machines, it will also report
|
|
a cryptic stack trace. This can often be turned into a sympolic stack
|
|
trace by invoking program "foo" with "callprocs foo". Callprocs is
|
|
a short shell script that invokes adb to expand program counter values
|
|
to symbolic addresses. It was largely supplied by Scott Schwartz.)
|
|
Note that the debugging facilities described in the next section can
|
|
sometimes be slightly LESS effective in leak finding mode, since in
|
|
leak finding mode, GC_debug_free actually results in reuse of the object.
|
|
(Otherwise the object is simply marked invalid.) Also note that the test
|
|
program is not designed to run meaningfully in FIND_LEAK mode.
|
|
Use "make gc.a" to build the collector.
|
|
|
|
DEBUGGING FACILITIES:
|
|
|
|
The routines GC_debug_malloc, GC_debug_malloc_atomic, GC_debug_realloc,
|
|
and GC_debug_free provide an alternate interface to the collector, which
|
|
provides some help with memory overwrite errors, and the like.
|
|
Objects allocated in this way are annotated with additional
|
|
information. Some of this information is checked during garbage
|
|
collections, and detected inconsistencies are reported to stderr.
|
|
|
|
Simple cases of writing past the end of an allocated object should
|
|
be caught if the object is explicitly deallocated, or if the
|
|
collector is invoked while the object is live. The first deallocation
|
|
of an object will clear the debugging info associated with an
|
|
object, so accidentally repeated calls to GC_debug_free will report the
|
|
deallocation of an object without debugging information. Out of
|
|
memory errors will be reported to stderr, in addition to returning
|
|
NIL.
|
|
|
|
GC_debug_malloc checking during garbage collection is enabled
|
|
with the first call to GC_debug_malloc. This will result in some
|
|
slowdown during collections. If frequent heap checks are desired,
|
|
this can be achieved by explicitly invoking GC_gcollect, e.g. from
|
|
the debugger.
|
|
|
|
GC_debug_malloc allocated objects should not be passed to GC_realloc
|
|
or GC_free, and conversely. It is however acceptable to allocate only
|
|
some objects with GC_debug_malloc, and to use GC_malloc for other objects,
|
|
provided the two pools are kept distinct. In this case, there is a very
|
|
low probablility that GC_malloc allocated objects may be misidentified as
|
|
having been overwritten. This should happen with probability at most
|
|
one in 2**32. This probability is zero if GC_debug_malloc is never called.
|
|
|
|
GC_debug_malloc, GC_malloc_atomic, and GC_debug_realloc take two
|
|
additional trailing arguments, a string and an integer. These are not
|
|
interpreted by the allocator. They are stored in the object (the string is
|
|
not copied). If an error involving the object is detected, they are printed.
|
|
|
|
The macros GC_MALLOC, GC_MALLOC_ATOMIC, GC_REALLOC, GC_FREE, and
|
|
GC_REGISTER_FINALIZER are also provided. These require the same arguments
|
|
as the corresponding (nondebugging) routines. If gc.h is included
|
|
with GC_DEBUG defined, they call the debugging versions of these
|
|
functions, passing the current file name and line number as the two
|
|
extra arguments, where appropriate. If gc.h is included without GC_DEBUG
|
|
defined, then all these macros will instead be defined to their nondebugging
|
|
equivalents. (GC_REGISTER_FINALIZER is necessary, since pointers to
|
|
objects with debugging information are really pointers to a displacement
|
|
of 16 bytes form the object beginning, and some translation is necessary
|
|
when finalization routines are invoked. For details, about what's stored
|
|
in the header, see the definition of the type oh in debug_malloc.c)
|
|
|
|
INCREMENTAL/GENERATIONAL COLLECTION:
|
|
|
|
The collector normally interrupts client code for the duration of
|
|
a garbage collection mark phase. This may be unacceptable if interactive
|
|
response is needed for programs with large heaps. The collector
|
|
can also run in a "generational" mode, in which it usually attempts to
|
|
collect only objects allocated since the last garbage collection.
|
|
Furthermore, in this mode, garbage collections run mostly incrementally,
|
|
with a small amount of work performed in response to each of a large number of
|
|
GC_malloc requests.
|
|
|
|
This mode is enabled by a call to GC_enable_incremental().
|
|
|
|
Incremental and generational collection is effective in reducing
|
|
pause times only if the collector has some way to tell which objects
|
|
or pages have been recently modified. The collector uses two sources
|
|
of information:
|
|
|
|
1. Information provided by the VM system. This may be provided in
|
|
one of several forms. Under Solaris 2.X (and potentially under other
|
|
similar systems) information on dirty pages can be read from the
|
|
/proc file system. Under other systems (currently SunOS4.X) it is
|
|
possible to write-protect the heap, and catch the resulting faults.
|
|
On these systems we require that system calls writing to the heap
|
|
(other than read) be handled specially by client code.
|
|
See os_dep.c for details.
|
|
|
|
2. Information supplied by the programmer. We define "stubborn"
|
|
objects to be objects that are rarely changed. Such an object
|
|
can be allocated (and enabled for writing) with GC_malloc_stubborn.
|
|
Once it has been initialized, the collector should be informed with
|
|
a call to GC_end_stubborn_change. Subsequent writes that store
|
|
pointers into the object must be preceded by a call to
|
|
GC_change_stubborn.
|
|
|
|
This mechanism performs best for objects that are written only for
|
|
initialization, and such that only one stubborn object is writable
|
|
at once. It is typically not worth using for short-lived
|
|
objects. Stubborn objects are treated less efficiently than pointerfree
|
|
(atomic) objects.
|
|
|
|
A rough rule of thumb is that, in the absence of VM information, garbage
|
|
collection pauses are proportional to the amount of pointerful storage
|
|
plus the amount of modified "stubborn" storage that is reachable during
|
|
the collection.
|
|
|
|
Initial allocation of stubborn objects takes longer than allocation
|
|
of other objects, since other data structures need to be maintained.
|
|
|
|
We recommend against random use of stubborn objects in client
|
|
code, since bugs caused by inappropriate writes to stubborn objects
|
|
are likely to be very infrequently observed and hard to trace.
|
|
However, their use may be appropriate in a few carefully written
|
|
library routines that do not make the objects themselves available
|
|
for writing by client code.
|
|
|
|
|
|
BUGS:
|
|
|
|
Any memory that does not have a recognizable pointer to it will be
|
|
reclaimed. Exclusive-or'ing forward and backward links in a list
|
|
doesn't cut it.
|
|
Some C optimizers may lose the last undisguised pointer to a memory
|
|
object as a consequence of clever optimizations. This has almost
|
|
never been observed in practice. Send mail to boehm@acm.org
|
|
for suggestions on how to fix your compiler.
|
|
This is not a real-time collector. In the standard configuration,
|
|
percentage of time required for collection should be constant across
|
|
heap sizes. But collection pauses will increase for larger heaps.
|
|
(On SPARCstation 2s collection times will be on the order of 300 msecs
|
|
per MB of accessible memory that needs to be scanned. Your mileage
|
|
may vary.) The incremental/generational collection facility helps,
|
|
but is portable only if "stubborn" allocation is used.
|
|
Please address bug reports to boehm@acm.org. If you are
|
|
contemplating a major addition, you might also send mail to ask whether
|
|
it's already been done (or whether we tried and discarded it).
|
|
|
|
RECENT VERSIONS:
|
|
|
|
Version 1.3 and immediately preceding versions contained spurious
|
|
assembly language assignments to TMP_SP. Only the assignment in the PC/RT
|
|
code is necessary. On other machines, with certain compiler options,
|
|
the assignments can lead to an unsaved register being overwritten.
|
|
Known to cause problems under SunOS 3.5 WITHOUT the -O option. (With
|
|
-O the compiler recognizes it as dead code. It probably shouldn't,
|
|
but that's another story.)
|
|
|
|
Version 1.4 and earlier versions used compile time determined values
|
|
for the stack base. This no longer works on Sun 3s, since Sun 3/80s use
|
|
a different stack base. We now use a straightforward heuristic on all
|
|
machines on which it is known to work (incl. Sun 3s) and compile-time
|
|
determined values for the rest. There should really be library calls
|
|
to determine such values.
|
|
|
|
Version 1.5 and earlier did not ensure 8 byte alignment for objects
|
|
allocated on a sparc based machine.
|
|
|
|
Version 1.8 added ULTRIX support in gc_private.h.
|
|
|
|
Version 1.9 fixed a major bug in gc_realloc.
|
|
|
|
Version 2.0 introduced a consistent naming convention for collector
|
|
routines and added support for registering dynamic library data segments
|
|
in the standard mark_roots.c. Most of the data structures were revamped.
|
|
The treatment of interior pointers was completely changed. Finalization
|
|
was added. Support for locking was added. Object kinds were added.
|
|
We added a black listing facility to avoid allocating at addresses known
|
|
to occur as integers somewhere in the address space. Much of this
|
|
was accomplished by adapting ideas and code from the PCR collector.
|
|
The test program was changed and expanded.
|
|
|
|
Version 2.1 was the first stable version since 1.9, and added support
|
|
for PPCR.
|
|
|
|
Version 2.2 added debugging allocation, and fixed various bugs. Among them:
|
|
- GC_realloc could fail to extend the size of the object for certain large object sizes.
|
|
- A blatant subscript range error in GC_printf, which unfortunately
|
|
wasn't exercised on machines with sufficient stack alignment constraints.
|
|
- GC_register_displacement did the wrong thing if it was called after
|
|
any allocation had taken place.
|
|
- The leak finding code would eventually break after 2048 byte
|
|
byte objects leaked.
|
|
- interface.c didn't compile.
|
|
- The heap size remained much too small for large stacks.
|
|
- The stack clearing code behaved badly for large stacks, and perhaps
|
|
on HP/PA machines.
|
|
|
|
Version 2.3 added ALL_INTERIOR_POINTERS and fixed the following bugs:
|
|
- Missing declaration of etext in the A/UX version.
|
|
- Some PCR root-finding problems.
|
|
- Blacklisting was not 100% effective, because the plausible future
|
|
heap bounds were being miscalculated.
|
|
- GC_realloc didn't handle out-of-memory correctly.
|
|
- GC_base could return a nonzero value for addresses inside free blocks.
|
|
- test.c wasn't really thread safe, and could erroneously report failure
|
|
in a multithreaded environment. (The locking primitives need to be
|
|
replaced for other threads packages.)
|
|
- GC_CONS was thoroughly broken.
|
|
- On a SPARC with dynamic linking, signals stayed diabled while the
|
|
client code was running.
|
|
(Thanks to Manuel Serrano at INRIA for reporting the last two.)
|
|
|
|
Version 2.4 added GC_free_space_divisor as a tuning knob, added
|
|
support for OS/2 and linux, and fixed the following bugs:
|
|
- On machines with unaligned pointers (e.g. Sun 3), every 128th word could
|
|
fail to be considered for marking.
|
|
- Dynamic_load.c erroneously added 4 bytes to the length of the data and
|
|
bss sections of the dynamic library. This could result in a bad memory
|
|
reference if the actual length was a multiple of a page. (Observed on
|
|
Sun 3. Can probably also happen on a Sun 4.)
|
|
(Thanks to Robert Brazile for pointing out that the Sun 3 version
|
|
was broken. Dynamic library handling is still broken on Sun 3s
|
|
under 4.1.1U1, but apparently not 4.1.1. If you have such a machine,
|
|
use -Bstatic.)
|
|
|
|
Version 2.5 fixed the following bugs:
|
|
- Removed an explicit call to exit(1)
|
|
- Fixed calls to GC_printf and GC_err_printf, so the correct number of
|
|
arguments are always supplied. The OS/2 C compiler gets confused if
|
|
the number of actuals and the number of formals differ. (ANSI C
|
|
doesn't require this to work. The ANSI sanctioned way of doing things
|
|
causes too many compatibility problems.)
|
|
|
|
Version 3.0 added generational/incremental collection and stubborn
|
|
objects.
|
|
|
|
Version 3.1 added the following features:
|
|
- A workaround for a SunOS 4.X SPARC C compiler
|
|
misfeature that caused problems when the collector was turned into
|
|
a dynamic library.
|
|
- A fix for a bug in GC_base that could result in a memory fault.
|
|
- A fix for a performance bug (and several other misfeatures) pointed
|
|
out by Dave Detlefs and Al Dosser.
|
|
- Use of dirty bit information for static data under Solaris 2.X.
|
|
- DEC Alpha/OSF1 support (thanks to Al Dosser).
|
|
- Incremental collection on more platforms.
|
|
- A more refined heap expansion policy. Less space usage by default.
|
|
- Various minor enhancements to reduce space usage, and to reduce
|
|
the amount of memory scanned by the collector.
|
|
- Uncollectable allocation without per object overhead.
|
|
- More conscientious handling of out-of-memory conditions.
|
|
- Fixed a bug in debugging stubborn allocation.
|
|
- Fixed a bug that resulted in occasional erroneous reporting of smashed
|
|
objects with debugging allocation.
|
|
- Fixed bogus leak reports of size 4096 blocks with FIND_LEAK.
|
|
|
|
Version 3.2 fixed a serious and not entirely repeatable bug in
|
|
the incremental collector. It appeared only when dirty bit info
|
|
on the roots was available, which is normally only under Solaris.
|
|
It also added GC_general_register_disappearing_link, and some
|
|
testing code. Interface.c disappeared.
|
|
|
|
Version 3.3 fixes several bugs and adds new ports:
|
|
- PCR-specific bugs.
|
|
- Missing locking in GC_free, redundant FASTUNLOCK
|
|
in GC_malloc_stubborn, and 2 bugs in
|
|
GC_unregister_disappearing_link.
|
|
All of the above were pointed out by Neil Sharman
|
|
(neil@cs.mu.oz.au).
|
|
- Common symbols allocated by the SunOS4.X dynamic loader
|
|
were not included in the root set.
|
|
- Bug in GC_finalize (reported by Brian Beuning and Al Dosser)
|
|
- Merged Amiga port from Jesper Peterson (untested)
|
|
- Merged NeXT port from Thomas Funke (significantly
|
|
modified and untested)
|
|
|
|
Version 3.4:
|
|
- Fixed a performance bug in GC_realloc.
|
|
- Updated the amiga port.
|
|
- Added NetBSD and 386BSD ports.
|
|
- Added cord library.
|
|
- Added trivial performance enhancement for
|
|
ALL_INTERIOR_POINTERS. (Don't scan last word.)
|
|
|
|
Version 3.5
|
|
- Minor collections now mark from roots only once, if that
|
|
doesn't cause an excessive pause.
|
|
- The stack clearing heuristic was refined to prevent anomalies
|
|
with very heavily recursive programs and sparse stacks.
|
|
- Fixed a bug that prevented mark stack growth in some cases.
|
|
GC_objects_are_marked should be set to TRUE after a call
|
|
to GC_push_roots and as part of GC_push_marked, since
|
|
both can now set mark bits. I think this is only a performance
|
|
bug, but I wouldn't bet on it. It's certainly very hard to argue
|
|
that the old version was correct.
|
|
- Fixed an incremental collection bug that prevented it from
|
|
working at all when HBLKSIZE != getpagesize()
|
|
- Changed dynamic_loading.c to include gc_priv.h before testing
|
|
DYNAMIC_LOADING. SunOS dynamic library scanning
|
|
must have been broken in 3.4.
|
|
- Object size rounding now adapts to program behavior.
|
|
- Added a workaround (provided by Manuel Serrano and
|
|
colleagues) to a long-standing SunOS 4.X (and 3.X?) ld bug
|
|
that I had incorrectly assumed to have been squished.
|
|
The collector was broken if the text segment size was within
|
|
32 bytes of a multiple of 8K bytes, and if the beginning of
|
|
the data segment contained interesting roots. The workaround
|
|
assumes a demand-loadable executable. The original may have
|
|
have "worked" in some other cases.
|
|
- Added dynamic library support under IRIX5.
|
|
- Added support for EMX under OS/2 (thanks to Ari Huttunen).
|
|
|
|
Version 3.6:
|
|
- fixed a bug in the mark stack growth code that was introduced
|
|
in 3.4.
|
|
- fixed Makefile to work around DEC AXP compiler tail recursion
|
|
bug.
|
|
|
|
Version 3.7:
|
|
- Added a workaround for an HP/UX compiler bug.
|
|
- Fixed another stack clearing performance bug. Reworked
|
|
that code once more.
|
|
|
|
Version 4.0:
|
|
- Added support for Solaris threads (which was possible
|
|
only by reimplementing some fraction of Solaris threads,
|
|
since Sun doesn't currently make the thread debugging
|
|
interface available).
|
|
- Added non-threads win32 and win32S support.
|
|
- (Grudgingly, with suitable muttering of obscenities) renamed
|
|
files so that the collector distribution could live on a FAT
|
|
file system. Files that are guaranteed to be useless on
|
|
a PC still have long names. Gc_inline.h and gc_private.h
|
|
still exist, but now just include gc_inl.h and gc_priv.h.
|
|
- Fixed a really obscure bug in finalization that could cause
|
|
undetected mark stack overflows. (I would be surprised if
|
|
any real code ever tickled this one.)
|
|
- Changed finalization code to dynamically resize the hash
|
|
tables it maintains. (This probably does not matter for well-
|
|
-written code. It no doubt does for C++ code that overuses
|
|
destructors.)
|
|
- Added typed allocation primitives. Rewrote the marker to
|
|
accommodate them with more reasonable efficiency. This
|
|
change should also speed up marking for GC_malloc allocated
|
|
objects a little. See gc_typed.h for new primitives.
|
|
- Improved debugging facilities slightly. Allocation time
|
|
stack traces are now kept by default on SPARC/SUNOS4.
|
|
(Thanks to Scott Schwartz.)
|
|
- Added better support for small heap applications.
|
|
- Significantly extended cord package. Fixed a bug in the
|
|
implementation of lazily read files. Printf and friends now
|
|
have cord variants. Cord traversals are a bit faster.
|
|
- Made ALL_INTERIOR_POINTERS recognition the default.
|
|
- Fixed de so that it can run in constant space, independent
|
|
of file size. Added simple string searching to cords and de.
|
|
- Added the Hull-Ellis C++ interface.
|
|
- Added dynamic library support for OSF/1.
|
|
(Thanks to Al Dosser and Tim Bingham at DEC.)
|
|
- Changed argument to GC_expand_hp to be expressed
|
|
in units of bytes instead of heap blocks. (Necessary
|
|
since the heap block size now varies depending on
|
|
configuration. The old version was never very clean.)
|
|
- Added GC_get_heap_size(). The previous "equivalent"
|
|
was broken.
|
|
- Restructured the Makefile a bit.
|
|
|
|
Since version 4.0:
|
|
- Changed finalization implementation to guarantee that
|
|
finalization procedures are called outside of the allocation
|
|
lock, making direct use of the interface a little less dangerous.
|
|
MAY BREAK EXISTING CLIENTS that assume finalizers
|
|
are protected by a lock. Since there seem to be few multithreaded
|
|
clients that use finalization, this is hopefully not much of
|
|
a problem.
|
|
- Fixed a gross bug in CORD_prev.
|
|
- Fixed a bug in blacklst.c that could result in unbounded
|
|
heap growth during startup on machines that do not clear
|
|
memory obtained from the OS (e.g. win32S).
|
|
- Ported de editor to win32/win32S. (This is now the only
|
|
version with a mouse-sensitive UI.)
|
|
- Added GC_malloc_ignore_off_page to allocate large arrays
|
|
in the presence of ALL_INTERIOR_POINTERS.
|
|
- Changed GC_call_with_alloc_lock to not disable signals in
|
|
the single-threaded case.
|
|
- Reduced retry count in GC_collect_or_expand for garbage
|
|
collecting when out of memory.
|
|
- Made uncollectable allocations bypass black-listing, as they
|
|
should.
|
|
- Fixed a bug in typed_test in test.c that could cause (legitimate)
|
|
GC crashes.
|
|
- Fixed some potential synchronization problems in finalize.c
|
|
- Fixed a real locking problem in typd_mlc.c.
|
|
- Worked around an AIX 3.2 compiler feature that results in
|
|
out of bounds memory references.
|
|
- Partially worked around an IRIX5.2 beta problem (which may
|
|
or may not persist to the final release).
|
|
- Fixed a bug in the heap integrity checking code that could
|
|
result in explicitly deallocated objects being identified as
|
|
smashed. Fixed a bug in the dbg_mlc stack saving code
|
|
that caused old argument pointers to be considered live.
|
|
- Fixed a bug in CORD_ncmp (and hence CORD_str).
|
|
- Repaired the OS2 port, which had suffered from bit rot
|
|
in 4.0. Worked around what appears to be CSet/2 V1.0
|
|
optimizer bug.
|
|
- Fixed a Makefile bug for target "c++".
|
|
|
|
Since version 4.1:
|
|
- Multiple bug fixes/workarounds in the Solaris threads version.
|
|
(It occasionally failed to locate some register contents for
|
|
marking. It also turns out that thr_suspend and friends are
|
|
unreliable in Solaris 2.3. Dirty bit reads appear
|
|
to be unreliable under some weird
|
|
circumstances. My stack marking code
|
|
contained a serious performance bug. The new code is
|
|
extremely defensive, and has not failed in several cpu
|
|
hours of testing. But no guarantees ...)
|
|
- Added MacOS support (thanks to Patrick Beard.)
|
|
- Fixed several syntactic bugs in gc_c++.h and friends. (These
|
|
didn't bother g++, but did bother most other compilers.)
|
|
Fixed gc_c++.h finalization interface. (It didn't.)
|
|
- 64 bit alignment for allocated objects was not guaranteed in a
|
|
few cases in which it should have been.
|
|
- Added GC_malloc_atomic_ignore_off_page.
|
|
- Added GC_collect_a_little.
|
|
- Added some prototypes to gc.h.
|
|
- Some other minor bug fixes (notably in Makefile).
|
|
- Fixed OS/2 / EMX port (thanks to Ari Huttunen).
|
|
- Fixed AmigaDOS port. (thanks to Michel Schinz).
|
|
- Fixed the DATASTART definition under Solaris. There
|
|
was a 1 in 16K chance of the collector missing the first
|
|
64K of static data (and thus crashing).
|
|
- Fixed some blatant anachronisms in the README file.
|
|
- Fixed PCR-Makefile for upcoming PPCR release.
|
|
|
|
Since version 4.2:
|
|
- Fixed SPARC alignment problem with GC_DEBUG.
|
|
- Fixed Solaris threads /proc workaround. The real
|
|
problem was an interaction with mprotect.
|
|
- Incorporated fix from Patrick Beard for gc_c++.h (now gc_cpp.h).
|
|
- Slightly improved allocator space utilization by
|
|
fixing the GC_size_map mechanism.
|
|
- Integrated some Sony News and MIPS RISCos 4.51
|
|
patches. (Thanks to Nobuyuki Hikichi of
|
|
Software Research Associates, Inc. Japan)
|
|
- Fixed HP_PA alignment problem. (Thanks to
|
|
xjam@cork.cs.berkeley.edu.)
|
|
- Added GC_same_obj and friends. Changed GC_base
|
|
to return 0 for pointers past the end of large objects.
|
|
Improved GC_base performance with ALL_INTERIOR_POINTERS
|
|
on machines with a slow integer mod operation.
|
|
Added GC_PTR_ADD, GC_PTR_STORE, etc. to prepare
|
|
for preprocessor.
|
|
- changed the default on most UNIX machines to be that
|
|
signals are not disabled during critical GC operations.
|
|
This is still ANSI-conforming, though somewhat dangerous
|
|
in the presence of signal handlers. But the performance
|
|
cost of the alternative is sometimes problematic.
|
|
Can be changed back with a minor Makefile edit.
|
|
- renamed IS_STRING in gc.h, to CORD_IS_STRING, thus
|
|
following my own naming convention. Added the function
|
|
CORD_to_const_char_star.
|
|
- Fixed a gross bug in GC_finalize. Symptom: occasional
|
|
address faults in that function. (Thanks to Anselm
|
|
Baird-Smith (Anselm.BairdSmith@inria.fr)
|
|
- Added port to ICL DRS6000 running DRS/NX. Restructured
|
|
things a bit to factor out common code, and remove obsolete
|
|
code. Collector should now run under SUNOS5 with either
|
|
mprotect or /proc dirty bits. (Thanks to Douglas Steel
|
|
(doug@wg.icl.co.uk)).
|
|
- More bug fixes and workarounds for Solaris 2.X. (These were
|
|
mostly related to putting the collector in a dynamic library,
|
|
which didn't really work before. Also SOLARIS_THREADS
|
|
didn't interact well with dl_open.) Thanks to btlewis@eng.sun.com.
|
|
- Fixed a serious performance bug on the DEC Alpha. The text
|
|
segment was getting registered as part of the root set.
|
|
(Amazingly, the result was still fast enough that the bug
|
|
was not conspicuous.) The fix works on OSF/1, version 1.3.
|
|
Hopefully it also works on other versions of OSF/1 ...
|
|
- Fixed a bug in GC_clear_roots.
|
|
- Fixed a bug in GC_generic_malloc_words_small that broke
|
|
gc_inl.h. (Reported by Antoine de Maricourt. I broke it
|
|
in trying to tweak the Mac port.)
|
|
- Fixed some problems with cord/de under Linux.
|
|
- Fixed some cord problems, notably with CORD_riter4.
|
|
- Added DG/UX port.
|
|
Thanks to Ben A. Mesander (ben@piglet.cr.usgs.gov)
|
|
- Added finalization registration routines with weaker ordering
|
|
constraints. (This is necessary for C++ finalization with
|
|
multiple inheritance, since the compiler often adds self-cycles.)
|
|
- Filled the holes in the SCO port. (Thanks to Michael Arnoldus
|
|
<chime@proinf.dk>.)
|
|
- John Ellis' additions to the C++ support: From John:
|
|
|
|
* I completely rewrote the documentation in the interface gc_c++.h
|
|
(later renamed gc_cpp.h). I've tried to make it both clearer and more
|
|
precise.
|
|
|
|
* The definition of accessibility now ignores pointers from an
|
|
finalizable object (an object with a clean-up function) to itself.
|
|
This allows objects with virtual base classes to be finalizable by the
|
|
collector. Compilers typically implement virtual base classes using
|
|
pointers from an object to itself, which under the old definition of
|
|
accessibility prevented objects with virtual base classes from ever
|
|
being collected or finalized.
|
|
|
|
* gc_cleanup now includes gc as a virtual base. This was enabled by
|
|
the change in the definition of accessibility.
|
|
|
|
* I added support for operator new[]. Since most (all?) compilers
|
|
don't yet support operator new[], it is conditionalized on
|
|
-DOPERATOR_NEW_ARRAY. The code is untested, but its trivial and looks
|
|
correct.
|
|
|
|
* The test program test_gc_c++ (later renamed test_cpp.cc)
|
|
tries to test for the C++-specific functionality not tested by the
|
|
other programs.
|
|
- Added <unistd.h> include to misc.c. (Needed for ppcr.)
|
|
- Added PowerMac port. (Thanks to Patrick Beard again.)
|
|
- Fixed "srcdir"-related Makefile problems. Changed things so
|
|
that all externally visible include files always appear in the
|
|
include subdirectory of the source. Made gc.h directly
|
|
includable from C++ code. (These were at Per
|
|
Bothner's suggestion.)
|
|
- Changed Intel code to also mark from ebp (Kevin Warne's
|
|
suggestion).
|
|
- Renamed C++ related files so they could live in a FAT
|
|
file system. (Charles Fiterman's suggestion.)
|
|
- Changed Windows NT Makefile to include C++ support in
|
|
gc.lib. Added C++ test as Makefile target.
|
|
|
|
Since version 4.3:
|
|
- ASM_CLEAR_CODE was erroneously defined for HP
|
|
PA machines, resulting in a compile error.
|
|
- Fixed OS/2 Makefile to create a library. (Thanks to
|
|
Mark Boulter (mboulter@vnet.ibm.com)).
|
|
- Gc_cleanup objects didn't work if they were created on
|
|
the stack. Fixed.
|
|
- One copy of Gc_cpp.h in the distribution was out of
|
|
synch, and failed to document some known compiler
|
|
problems with explicit destructor invocation. Partially
|
|
fixed. There are probably other compilers on which
|
|
gc_cleanup is miscompiled.
|
|
- Fixed Makefile to pass C compiler flags to C++ compiler.
|
|
- Added Mac fixes.
|
|
- Fixed os_dep.c to work around what appears to be
|
|
a new and different VirtualQuery bug under newer
|
|
versions of win32S.
|
|
- GC_non_gc_bytes was not correctly maintained by
|
|
GC_free. Fixed. Thanks to James Clark (jjc@jclark.com).
|
|
- Added GC_set_max_heap_size.
|
|
- Changed allocation code to ignore blacklisting if it is preventing
|
|
use of a very large block of memory. This has the advantage
|
|
that naive code allocating very large objects is much more
|
|
likely to work. The downside is you might no
|
|
longer find out that such code should really use
|
|
GC_malloc_ignore_off_page.
|
|
- Changed GC_printf under win32 to close and reopen the file
|
|
between calls. FAT file systems otherwise make the log file
|
|
useless for debugging.
|
|
- Added GC_try_to_collect and GC_get_bytes_since_gc. These
|
|
allow starting an abortable collection during idle times.
|
|
This facility does not require special OS support. (Thanks to
|
|
Michael Spertus of Geodesic Systems for suggesting this. It was
|
|
actually an easy addition. Kumar Srikantan previously added a similar
|
|
facility to a now ancient version of the collector. At the time
|
|
this was much harder, and the result was less convincing.)
|
|
- Added some support for the Borland development environment. (Thanks
|
|
to John Ellis and Michael Spertus.)
|
|
- Removed a misfeature from checksums.c that caused unexpected
|
|
heap growth. (Thanks to Scott Schwartz.)
|
|
- Changed finalize.c to call WARN if it encounters a finalization cycle.
|
|
WARN is defined in gc_priv.h to write a message, usually to stdout.
|
|
In many environments, this may be inappropriate.
|
|
- Renamed NO_PARAMS in gc.h to GC_NO_PARAMS, thus adhering to my own
|
|
naming convention.
|
|
- Added GC_set_warn_proc to intercept warnings.
|
|
- Fixed Amiga port. (Thanks to Michel Schinz (schinz@alphanet.ch).)
|
|
- Fixed a bug in mark.c that could result in an access to unmapped
|
|
memory from GC_mark_from_mark_stack on machines with unaligned
|
|
pointers.
|
|
- Fixed a win32 specific performance bug that could result in scanning of
|
|
objects allocated with the system malloc.
|
|
- Added REDIRECT_MALLOC.
|
|
|
|
Since version 4.4:
|
|
- Fixed many minor and one major README bugs. (Thanks to Franklin Chen
|
|
(chen@adi.com) for pointing out many of them.)
|
|
- Fixed ALPHA/OSF/1 dynamic library support. (Thanks to Jonathan Bachrach
|
|
(jonathan@harlequin.com)).
|
|
- Added incremental GC support (MPROTECT_VDB) for Linux (with some
|
|
help from Bruno Haible).
|
|
- Altered SPARC recognition tests in gc.h and config.h (mostly as
|
|
suggested by Fergus Henderson).
|
|
- Added basic incremental GC support for win32, as implemented by
|
|
Windows NT and Windows 95. GC_enable_incremental is a noop
|
|
under win32s, which doesn't implement enough of the VM interface.
|
|
- Added -DLARGE_CONFIG.
|
|
- Fixed GC_..._ignore_off_page to also function without
|
|
-DALL_INTERIOR_POINTERS.
|
|
- (Hopefully) fixed RS/6000 port. (Only the test was broken.)
|
|
- Fixed a performance bug in the nonincremental collector running
|
|
on machines supporting incremental collection with MPROTECT_VDB
|
|
(e.g. SunOS 4, DEC AXP). This turned into a correctness bug under
|
|
win32s with win32 incremental collection. (Not all memory protection
|
|
was disabled.)
|
|
- Fixed some ppcr related bit rot.
|
|
- Caused dynamic libraries to be unregistered before reregistering.
|
|
The old way turned out to be a performance bug on some machines.
|
|
- GC_root_size was not properly maintained under MSWIN32.
|
|
- Added -DNO_DEBUGGING and GC_dump.
|
|
- Fixed a couple of bugs arising with SOLARIS_THREADS +
|
|
REDIRECT_MALLOC.
|
|
- Added NetBSD/M68K port. (Thanks to Peter Seebach
|
|
<seebs@taniemarie.solon.com>.)
|
|
- Fixed a serious realloc bug. For certain object sizes, the collector
|
|
wouldn't scan the expanded part of the object. (Thanks to Clay Spence
|
|
(cds@peanut.sarnoff.com) for noticing the problem, and helping me to
|
|
track it down.)
|
|
|
|
Since version 4.5:
|
|
- Added Linux ELF support. (Thanks to Arrigo Triulzi <arrigo@ic.ac.uk>.)
|
|
- GC_base crashed if it was called before any other GC_ routines.
|
|
This could happen if a gc_cleanup object was allocated outside the heap
|
|
before any heap allocation.
|
|
- The heap expansion heuristic was not stable if all objects had finalization
|
|
enabled. Fixed finalize.c to count memory in finalization queue and
|
|
avoid explicit deallocation. Changed alloc.c to also consider this count.
|
|
(This is still not recommended. It's expensive if nothing else.) Thanks
|
|
to John Ellis for pointing this out.
|
|
- GC_malloc_uncollectable(0) was broken. Thanks to Phong Vo for pointing
|
|
this out.
|
|
- The collector didn't compile under Linux 1.3.X. (Thanks to Fred Gilham for
|
|
pointing this out.) The current workaround is ugly, but expected to be
|
|
temporary.
|
|
- Fixed a formatting problem for SPARC stack traces.
|
|
- Fixed some '=='s in os_dep.c that should have been assignments.
|
|
Fortunately these were in code that should never be executed anyway.
|
|
(Thanks to Fergus Henderson.)
|
|
- Fixed the heap block allocator to only drop blacklisted blocks in small
|
|
chunks. Made BL_LIMIT self adjusting. (Both of these were in response
|
|
to heap growth observed by Paul Graham.)
|
|
- Fixed the Metrowerks/68K Mac code to also mark from a6. (Thanks
|
|
to Patrick Beard.)
|
|
- Significantly updated README.debugging.
|
|
- Fixed some problems with longjmps out of signal handlers, especially under
|
|
Solaris. Added a workaround for the fact that siglongjmp doesn't appear to
|
|
do the right thing with -lthread under Solaris.
|
|
- Added MSDOS/djgpp port. (Thanks to Mitch Harris (maharri@uiuc.edu).)
|
|
- Added "make reserved_namespace" and "make user_namespace". The
|
|
first renames ALL "GC_xxx" identifiers as "_GC_xxx". The second is the
|
|
inverse transformation. Note that doing this is guaranteed to break all
|
|
clients written for the other names.
|
|
- descriptor field for kind NORMAL in GC_obj_kinds with ADD_BYTE_AT_END
|
|
defined should be -ALIGNMENT not WORDS_TO_BYTES(-1). This is
|
|
a serious bug on machines with pointer alignment of less than a word.
|
|
- GC_ignore_self_finalize_mark_proc didn't handle pointers to very near the
|
|
end of the object correctly. Caused failures of the C++ test on a DEC Alpha
|
|
with g++.
|
|
- gc_inl.h still had problems. Partially fixed. Added warnings at the
|
|
beginning to hopefully specify the remaining dangers.
|
|
- Added DATAEND definition to config.h.
|
|
- Fixed some of the .h file organization. Fixed "make floppy".
|
|
|
|
Since version 4.6:
|
|
- Fixed some compilation problems with -DCHECKSUMS (thanks to Ian Searle)
|
|
- Updated some Mac specific files to synchronize with Patrick Beard.
|
|
- Fixed a serious bug for machines with non-word-aligned pointers.
|
|
(Thanks to Patrick Beard for pointing out the problem. The collector
|
|
should fail almost any conceivable test immediately on such machines.)
|
|
|
|
Since version 4.7:
|
|
- Changed a "comment" in a MacOS specific part of mach-dep.c that caused
|
|
gcc to fail on other platforms.
|
|
|
|
Since version 4.8
|
|
- More README.debugging fixes.
|
|
- Objects ready for finalization, but not finalized in the same GC
|
|
cycle, could be prematurely collected. This occasionally happened
|
|
in test_cpp.
|
|
- Too little memory was obtained from the system for very large
|
|
objects. That could cause a heap explosion if these objects were
|
|
not contiguous (e.g. under PCR), and too much of them was blacklisted.
|
|
- Due to an improper initialization, the collector was too hesitant to
|
|
allocate blacklisted objects immediately after system startup.
|
|
- Moved GC_arrays from the data into the bss segment by not explicitly
|
|
initializing it to zero. This significantly
|
|
reduces the size of executables, and probably avoids some disk accesses
|
|
on program startup. It's conceivable that it might break a port that I
|
|
didn't test.
|
|
- Fixed EMX_MAKEFILE to reflect the gc_c++.h to gc_cpp.h renaming which
|
|
occurred a while ago.
|
|
|
|
Since 4.9:
|
|
- Fixed a typo around a call to GC_collect_or_expand in alloc.c. It broke
|
|
handling of out of memory. (Thanks to Patrick Beard for noticing.)
|
|
|
|
Since 4.10:
|
|
- Rationalized (hopefully) GC_try_to_collect in an incremental collection
|
|
environment. It appeared to not handle a call while a collection was in
|
|
progress, and was otherwise too conservative.
|
|
- Merged GC_reclaim_or_delete_all into GC_reclaim_all to get rid of some
|
|
code.
|
|
- Added Patrick Beard's Mac fixes, with substantial completely untested
|
|
modifications.
|
|
- Fixed the MPROTECT_VDB code to deal with large pages and imprecise
|
|
fault addresses (as on an UltraSPARC running Solaris 2.5). Note that this
|
|
was not a problem in the default configuration, which uses PROC_VDB.
|
|
- The DEC Alpha assembly code needed to restore $gp between calls.
|
|
Thanks to Fergus Henderson for tracking this down and supplying a
|
|
patch.
|
|
- The write command for "de" was completely broken for large files.
|
|
I used the easiest portable fix, which involved changing the semantics
|
|
so that f.new is written instead of overwriting f. That's safer anyway.
|
|
- Added README.solaris2 with a discussion of the possible problems of
|
|
mixing the collector's sbrk allocation with malloc/realloc.
|
|
- Changed the data segment starting address for SGI machines. The
|
|
old code failed under IRIX6.
|
|
- Required double word alignment for MIPS.
|
|
- Various minor fixes to remove warnings.
|
|
- Attempted to fix some Solaris threads problems reported by Zhiying Chen.
|
|
In particular, the collector could try to fork a thread with the
|
|
world stopped as part of GC_thr_init. It also failed to deal with
|
|
the case in which the original thread terminated before the whole
|
|
process did.
|
|
- Added -DNO_EXECUTE_PERMISSION. This has a major performance impact
|
|
on the incremental collector under Irix, and perhaps under other
|
|
operating systems.
|
|
- Added some code to support allocating the heap with mmap. This may
|
|
be preferable under some circumstances.
|
|
- Integrated dynamic library support for HP.
|
|
(Thanks to Knut Tvedten <knuttv@ifi.uio.no>.)
|
|
- Integrated James Clark's win32 threads support, and made a number
|
|
of changes to it, many of which were suggested by Pontus Rydin.
|
|
This is still not 100% solid.
|
|
- Integrated Alistair Crooks' support for UTS4 running on an Amdahl
|
|
370-class machine.
|
|
- Fixed a serious bug in explicitly typed allocation. Objects requiring
|
|
large descriptors where handled in a way that usually resulted in
|
|
a segmentation fault in the marker. (Thanks to Jeremy Fitzhardinge
|
|
for helping to track this down.)
|
|
- Added partial support for GNU win32 development. (Thanks to Fergus
|
|
Henderson.)
|
|
- Added optional support for Java-style finalization semantics. (Thanks
|
|
to Patrick Bridges.) This is recommended only for Java implementations.
|
|
- GC_malloc_uncollectable faulted instead of returning 0 when out of
|
|
memory. (Thanks to dan@math.uiuc.edu for noticing.)
|
|
- Calls to GC_base before the collector was initialized failed on a
|
|
DEC Alpha. (Thanks to Matthew Flatt.)
|
|
- Added base pointer checking to GC_REGISTER_FINALIZER in debugging
|
|
mode, at the suggestion of Jeremy Fitzhardinge.
|
|
- GC_debug_realloc failed for uncollectable objects. (Thanks to
|
|
Jeremy Fitzhardinge.)
|
|
- Explicitly typed allocation could crash if it ran out of memory.
|
|
(Thanks to Jeremy Fitzhardinge.)
|
|
- Added minimal support for a DEC Alpha running Linux.
|
|
- Fixed a problem with allocation of objects whose size overflowed
|
|
ptrdiff_t. (This now fails unconditionally, as it should.)
|
|
- Added the beginning of Irix pthread support.
|
|
- Integrated Xiaokun Zhu's fixes for djgpp 2.01.
|
|
- Added SGI-style STL allocator support (gc_alloc.h).
|
|
- Fixed a serious bug in README.solaris2. Multithreaded programs must include
|
|
gc.h with SOLARIS_THREADS defined.
|
|
- Changed GC_free so it actually deallocates uncollectable objects.
|
|
(Thanks to Peter Chubb for pointing out the problem.)
|
|
- Added Linux ELF support for dynamic libararies. (Thanks again to
|
|
Patrick Bridges.)
|
|
- Changed the Borland cc configuration so that the assembler is not
|
|
required.
|
|
- Fixed a bug in the C++ test that caused it to fail in 64-bit
|
|
environments.
|
|
|
|
Since 4.11:
|
|
- Fixed ElfW definition in dyn_load.c. (Thanks to Fergus Henderson.)
|
|
This prevented the dynamic library support from compiling on some
|
|
older ELF Linux systems.
|
|
- Fixed UTS4 port (which I apparently mangled during the integration)
|
|
(Thanks to again to Alistair Crooks.)
|
|
- "Make C++" failed on Suns with SC4.0, due to a problem with "bool".
|
|
Fixed in gc_priv.h.
|
|
- Added more pieces for GNU win32. (Thanks to Timothy N. Newsham.)
|
|
The current state of things should suffice for at least some
|
|
applications.
|
|
- Changed the out of memory retry count handling as suggested by
|
|
Kenjiro Taura. (This matters only if GC_max_retries > 0, which
|
|
is no longer the default.)
|
|
- If a /proc read failed repeatedly, GC_written_pages was not updated
|
|
correctly. (Thanks to Peter Chubb for diagnosing this.)
|
|
- Under unlikely circumstances, the allocator could infinite loop in
|
|
an out of memory situation. (Thanks again to Kenjiro Taura for
|
|
identifying the problem and supplying a fix.)
|
|
- Fixed a syntactic error in the DJGPP code. (Thanks to Fergus
|
|
Henderson for finding this by inspection.) Also fixed a test program
|
|
problem with DJGPP (Thanks to Peter Monks.)
|
|
- Atomic uncollectable objects were not treated correctly by the
|
|
incremental collector. This resulted in weird log statistics and
|
|
occasional performance problems. (Thanks to Peter Chubb for pointing
|
|
this out.)
|
|
- Fixed some problems resulting from compilers that dont define
|
|
__STDC__. In this case void * and char * were used inconsistently
|
|
in some cases. (Void * should not have been used at all. If
|
|
you have an ANSI superset compiler that does not define __STDC__,
|
|
please compile with -D__STDC__=0. Thanks to Manuel Serrano and others
|
|
for pointing out the problem.)
|
|
- Fixed a compilation problem on Irix with -n32 and -DIRIX_THREADS.
|
|
Also fixed some other IRIX_THREADS problems which may or may not have
|
|
had observable symptoms.
|
|
- Fixed an HP PA compilation problem in dyn_load.c. (Thanks to
|
|
Philippe Queinnec.)
|
|
- SEGV fault handlers sometimes did not get reset correctly. (Thanks
|
|
to David Pickens.)
|
|
- Added a fix for SOLARIS_THREADS on Intel. (Thanks again to David
|
|
Pickens.) This probably needs more work to become functional.
|
|
- Fixed struct sigcontext_struct in os_dep.c for compilation under
|
|
Linux 2.1.X. (Thanks to Fergus Henderson.)
|
|
- Changed the DJGPP STACKBOTTOM and DATASTART values to those suggested
|
|
by Kristian Kristensen. These may still not be right, but it is
|
|
it is likely to work more often than what was there before. They may
|
|
even be exactly right.
|
|
- Added a #include <string.h> to test_cpp.cc. This appears to help
|
|
with HP/UX and gcc. (Thanks to assar@sics.se.)
|
|
- Version 4.11 failed to run in incremental mode on recent 64-bit Irix
|
|
kernels. This was a problem related to page unaligned heap segments.
|
|
Changed the code to page align heap sections on all platforms.
|
|
(I had mistakenly identified this as a kernel problem earlier.
|
|
It was not.)
|
|
- Version 4.11 did not make allocated storage executable, except on
|
|
one or two platforms, due to a bug in a #if test. (Thanks to Dave
|
|
Grove for pointing this out.)
|
|
- Added sparc_sunos4_mach_dep.s to support Sun's compilers under SunOS4.
|
|
- Added GC_exclude_static_roots.
|
|
- Fixed the object size mapping algorithm. This shouldn't matter,
|
|
but the old code was ugly.
|
|
- Heap checking code could die if one of the allocated objects was
|
|
larger than its base address. (Unsigned underflow problem. Thanks
|
|
to Clay Spence for isolating the problem.)
|
|
- Added RS6000 (AIX) dynamic library support and fixed STACK_BOTTOM.
|
|
(Thanks to Fred Stearns.)
|
|
- Added Fergus Henderson's patches for improved robustness with large
|
|
heaps and lots of blacklisting.
|
|
- Added Peter Chubb's changes to support Solaris Pthreads, to support
|
|
MMAP allocation in Solaris, to allow Solaris to find dynamic libraries
|
|
through /proc, to add malloc_typed_ignore_off_page, and a few other
|
|
minor features and bug fixes.
|
|
- The Solaris 2 port should not use sbrk. I received confirmation from
|
|
Sun that the use of sbrk and malloc in the same program is not
|
|
supported. The collector now defines USE_MMAP by default on Solaris.
|
|
- Replaced the djgpp makefile with Gary Leavens' version.
|
|
- Fixed MSWIN32 detection test.
|
|
- Added Fergus Henderson's patches to allow putting the collector into
|
|
a DLL under GNU win32.
|
|
- Added Ivan V. Demakov's port to Watcom C on X86.
|
|
- Added Ian Piumarta's Linux/PowerPC port.
|
|
- On Brian Burton's suggestion added PointerFreeGC to the placement
|
|
options in gc_cpp.h. This is of course unsafe, and may be controversial.
|
|
On the other hand, it seems to be needed often enough that it's worth
|
|
adding as a standard facility.
|
|
|
|
Since 4.12:
|
|
- Fixed a crucial bug in the Watcom port. There was a redundant decl
|
|
of GC_push_one in gc_priv.h.
|
|
- Added FINALIZE_ON_DEMAND.
|
|
- Fixed some pre-ANSI cc problems in test.c.
|
|
- Removed getpagesize() use for Solaris. It seems to be missing in one
|
|
or two versions.
|
|
- Fixed bool handling for SPARCCompiler version 4.2.
|
|
- Fixed some files in include that had gotten unlinked from the main
|
|
copy.
|
|
- Some RS/6000 fixes (missing casts). Thanks to Toralf Foerster.
|
|
- Fixed several problems in GC_debug_realloc, affecting mostly the
|
|
FIND_LEAK case.
|
|
- GC_exclude_static_roots contained a buggy unsigned comparison to
|
|
terminate a loop. (Thanks to Wilson Ho.)
|
|
- CORD_str failed if the substring occurred at the last possible position.
|
|
(Only affects cord users.)
|
|
- Fixed Linux code to deal with RedHat 5.0 and integrated Peter Bigot's
|
|
os_dep.c code for dealing with various Linux versions.
|
|
- Added workaround for Irix pthreads sigaction bug and possible signal
|
|
misdirection problems.
|
|
Since alpha1:
|
|
- Changed RS6000 STACKBOTTOM.
|
|
- Integrated Patrick Beard's Mac changes.
|
|
- Alpha1 didn't compile on Irix m.n, m < 6.
|
|
- Replaced Makefile.dj with a new one from Gary Leavens.
|
|
- Added Andrew Stitcher's changes to support SCO OpenServer.
|
|
- Added PRINT_BLACK_LIST, to allow debugging of high densities of false
|
|
pointers.
|
|
- Added code to debug allocator to keep track of return address
|
|
in GC_malloc caller, thus giving a bit more context.
|
|
- Changed default behavior of large block allocator to more
|
|
aggressively avoid fragmentation. This is likely to slow down the
|
|
collector when it succeeds at reducing space cost.
|
|
- Integrated Fergus Henderson's CYGWIN32 changes. They are untested,
|
|
but needed for newer versions.
|
|
- USE_MMAP had some serious bugs. This caused the collector to fail
|
|
consistently on Solaris with -DSMALL_CONFIG.
|
|
- Added Linux threads support, thanks largely to Fergus Henderson.
|
|
Since alpha2:
|
|
- Fixed more Linux threads problems.
|
|
- Changed default GC_free_space_divisor to 3 with new large block allocation.
|
|
(Thanks to Matthew Flatt for some measurements that suggest the old
|
|
value sometimes favors space too much over time.)
|
|
- More CYGWIN32 fixes.
|
|
- Integrated Tyson-Dowd's Linux-M68K port.
|
|
- Minor HP PA and DEC UNIX fixes from Fergus Henderson.
|
|
- Integrated Christoffe Raffali's Linux-SPARC changes.
|
|
- Allowed for one more GC fixup iteration after a full GC in incremental
|
|
mode. Some quick measurements suggested that this significantly
|
|
reduces pause times even with smaller GC_RATE values.
|
|
- Moved some more GC data structures into GC_arrays. This decreases
|
|
pause times and GC overhead, but makes debugging slightly less convenient.
|
|
- Fixed namespace pollution problem ("excl_table").
|
|
- Made GC_incremental a constant for -DSMALL_CONFIG, hopefully shrinking
|
|
that slightly.
|
|
- Added some win32 threads fixes.
|
|
- Integrated Ivan Demakov and David Stes' Watcom fixes.
|
|
- Various other minor fixes contributed by many people.
|
|
- Renamed config.h to gcconfig.h, since config.h tends to be used for
|
|
many other things.
|
|
- Integrated Matthew Flatt's support for 68K MacOS "far globals".
|
|
- Fixed up some of the dynamic library Makefile targets for consistency
|
|
across platforms.
|
|
- Fixed a USE_MMAP typo that caused out-of-memory handling to fail
|
|
on Solaris.
|
|
- Added code to test.c to test thread creation a bit more.
|
|
- Integrated GC_win32_free_heap, as suggested by Ivan Demakov.
|
|
- Fixed Solaris 2.7 stack base finding problem. (This may actually
|
|
have been done in an earlier alpha release.)
|
|
Since alpha3:
|
|
- Fixed MSWIN32 recognition test, which interfered with cygwin.
|
|
- Removed unnecessary gc_watcom.asm from distribution. Removed
|
|
some obsolete README.win32 text.
|
|
- Added Alpha Linux incremental GC support. (Thanks to Philipp Tomsich
|
|
for code for retrieving the fault address in a signal handler.)
|
|
Changed Linux signal handler context argument to be a pointer.
|
|
- Took care of some new warnings generated by the 7.3 SGI compiler.
|
|
- Integrated Phillip Musumeci's FreeBSD/ELF fixes.
|
|
- -DIRIX_THREADS was broken with the -o32 ABI (typo in gc_priv.h>
|
|
|
|
Since 4.13:
|
|
- Fixed GC_print_source_ptr to not use a prototype.
|
|
- generalized CYGWIN test.
|
|
- gc::new did the wrong thing with PointerFreeGC placement.
|
|
(Thanks to Rauli Ruohonen.)
|
|
- In the ALL_INTERIOR_POINTERS (default) case, some callee-save register
|
|
values could fail to be scanned if the register was saved and
|
|
reused in a GC frame. This showed up in verbose mode with gctest
|
|
compiled with an unreleased SGI compiler. I vaguely recall an old
|
|
bug report that may have been related. The bug was probably quite old.
|
|
(The problem was that the stack scanning could be deferred until
|
|
after the relevant frame was overwritten, and the new save location
|
|
might be outside the scanned area. Fixed by more eager stack scanning.)
|
|
- PRINT_BLACK_LIST had some problems. A few source addresses were garbage.
|
|
- Replaced Makefile.dj and added -I flags to cord make targets.
|
|
(Thanks to Gary Leavens.)
|
|
- GC_try_to_collect was broken with the nonincremental collector.
|
|
- gc_cleanup destructors could pass the wrong address to
|
|
GC_register_finalizer_ignore_self in the presence of multiple
|
|
inheritance. (Thanks to Darrell Schiebel.)
|
|
- Changed PowerPC Linux stack finding code.
|
|
|
|
Since 4.14alpha1
|
|
- -DSMALL_CONFIG did not work reliably with large (> 4K) pages.
|
|
Recycling the mark stack during expansion could result in a size
|
|
zero heap segment, which confused things. (This was probably also an
|
|
issue with the normal config and huge pages.)
|
|
- Did more work to make sure that callee-save registers were scanned
|
|
completely, even with the setjmp-based code. Added USE_GENERIC_PUSH_REGS
|
|
macro to facilitate testing on machines I have access to.
|
|
- Added code to explicitly push register contents for win32 threads.
|
|
This seems to be necessary. (Thanks to Pierre de Rop.)
|
|
|
|
Since 4.14alpha2
|
|
- changed STACKBOTTOM for DJGPP (Thanks to Salvador Eduardo Tropea).
|
|
|
|
Since 4.14
|
|
- Reworked large block allocator. Now uses multiple doubly linked free
|
|
lists to approximate best fit.
|
|
- Changed heap expansion heuristic. Entirely free blocks are no longer
|
|
counted towards the heap size. This seems to have a major impact on
|
|
heap size stability; the old version could expand the heap way too
|
|
much in the presence of large block fragmentation.
|
|
- added -DGC_ASSERTIONS and some simple assertions inside the collector.
|
|
This is mainlyt for collector debugging.
|
|
- added -DUSE_MUNMAP to allow the heap to shrink. Suupported on only
|
|
a few UNIX-like platforms for now.
|
|
- added GC_dump_regions() for debugging of fragmentation issues.
|
|
- Changed PowerPC pointer alignment under Linux to 4. (This needs
|
|
checking by someone who has one. The suggestions came to me via a
|
|
rather circuitous path.)
|
|
- Changed the Linux/Alpha port to walk the data segment backwards until
|
|
it encounters a SIGSEGV. The old way to find the start of the data
|
|
segment broke with a recent release.
|
|
- cordxtra.c needed to call GC_REGISTER_FINALIZER instead of
|
|
GC_register_finalizer, so that it would continue to work with GC_DEBUG.
|
|
- allochblk sometimes cleared the wrong block for debugging purposes
|
|
when it dropped blacklisted blocks. This could result in spurious
|
|
error reports with GC_DEBUG.
|
|
- added MACOS X Server support. (Thanks to Andrew Stone.)
|
|
- Changed the Solaris threads code to ignore stack limits > 8 MB with
|
|
a warning. Empirically, it is not safe to access arbitrary pages
|
|
in such large stacks. And the dirty bit implementation does not
|
|
guarantee that none of them will be accessed.
|
|
- Integrated Martin Tauchmann's Amiga changes.
|
|
- Integrated James Dominy's OpenBSD/SPARC port.
|
|
|
|
Since 5.0alpha1
|
|
- Fixed bugs introduced in alpha1 (OpenBSD & large block initialization).
|
|
- Added -DKEEP_BACK_PTRS and backptr.h interface. (The implementation
|
|
idea came from Al Demers.)
|
|
|
|
Since 5.0alpha2
|
|
- Added some highly incomplete code to support a copied young generation.
|
|
Comments on nursery.h are appreciated.
|
|
- Changed -DFIND_LEAK, -DJAVA_FINALIZATION, and -DFINALIZE_ON_DEMAND,
|
|
so the same effect could be obtained with a runtime switch. This is
|
|
a step towards standardizing on a single dynamic GC library.
|
|
- Significantly changed the way leak detection is handled, as a consequence
|
|
of the above.
|
|
|
|
Since 5.0 alpha3
|
|
- Added protection fault handling patch for Linux/M68K from Fergus
|
|
Henderson and Roman Hodek.
|
|
- Removed the tests for SGI_SOURCE in new_gc_alloc.h. This was causing that
|
|
interface to fail on nonSGI platforms.
|
|
- Changed the Linux stack finding code to use /proc, after changing it
|
|
to use HEURISTIC1. (Thanks to David Mossberger for pointing out the
|
|
/proc hook.)
|
|
- Added HP/UX incremental GC support and HP/UX 11 thread support.
|
|
Thread support is currently still flakey.
|
|
- Added basic Linux/IA64 support.
|
|
- Integrated Anthony Green's PicoJava support.
|
|
- Integrated Scott Ananian's StrongARM/NetBSD support.
|
|
- Fixed some fairly serious performance bugs in the incremental
|
|
collector. These have probably been there essentially forever.
|
|
(Mark bits were sometimes set before scanning dirty pages.
|
|
The reclaim phase unnecessarily dirtied full small object pages.)
|
|
- Changed the reclaim phase to ignore nearly full pages to avoid
|
|
touching them.
|
|
- Limited GC_black_list_spacing to roughly the heap growth increment.
|
|
- Changed full collection triggering heuristic to decrease full GC
|
|
frequency by default, but to explicitly trigger full GCs during
|
|
heap growth. This doesn't always improve things, but on average it's
|
|
probably a win.
|
|
- GC_debug_free(0, ...) failed. Thanks to Fergus Henderson for the
|
|
bug report and fix.
|
|
|
|
Since 5.0 alpha4
|
|
- GC_malloc_explicitly_typed and friends sometimes failed to
|
|
initialize first word.
|
|
- Added allocation routines and support in the marker for mark descriptors
|
|
in a type structure referenced by the first word of an object. This was
|
|
introduced to support gcj, but hopefully in a way that makes it
|
|
generically useful.
|
|
- Added GC_requested_heapsize, and inhibited collections in nonincremental
|
|
mode if the actual used heap size is less than what was explicitly
|
|
requested.
|
|
- The Solaris pthreads version of GC_pthread_create didn't handle a NULL
|
|
attribute pointer. Solaris thread support used the wrong default thread
|
|
stack size. (Thanks to Melissa O'Neill for the patch.)
|
|
- Changed PUSH_CONTENTS macro to no longer modify first parameter.
|
|
This usually doesn't matter, but it was certainly an accident waiting
|
|
to happen ...
|
|
- Added GC_register_finalizer_no_order and friends to gc.h. They're
|
|
needed by Java implementations.
|
|
- Integrated a fix for a win32 deadlock resulting from clock() calling
|
|
malloc. (Thanks to Chris Dodd.)
|
|
- Integrated Hiroshi Kawashima's port to Linux/MIPS. This was designed
|
|
for a handheld platform, and may or may not be sufficient for other
|
|
machines.
|
|
- Fixed a va_arg problem with the %c specifier in cordprnt.c. It appears
|
|
that this was always broken, but recent versions of gcc are the first to
|
|
report the (statically detectable) bug.
|
|
- Added an attempt at a more general solution to dlopen races/deadlocks.
|
|
GC_dlopen now temporarily disables collection. Still not ideal, but ...
|
|
- Added -DUSE_I686_PREFETCH, -DUSE_3DNOW_PREFETCH, and support for IA64
|
|
prefetch instructions. May improve performance measurably, but I'm not
|
|
sure the code will run correctly on processors that don't support the
|
|
instruction. Won't build except with very recent gcc.
|
|
- Added caching for header lookups in the marker. This seems to result
|
|
in a barely measurable performance gain. Added support for interleaved
|
|
lookups of two pointers, but unconfigured that since the performance
|
|
gain is currently near zero, and it adds to code size.
|
|
- Changed Linux DATA_START definition to check both data_start and
|
|
__data_start, since nothing else seems to be portable.
|
|
- Added -DUSE_LD_WRAP to optionally take advantage of the GNU ld function
|
|
wrapping mechanism. Probably currently useful only on Linux.
|
|
- Moved some variables for the scratch allocator into GC_arrays, on
|
|
Martin Hirzel's suggestion.
|
|
- Fixed a win32 threads bug that caused the collector to not look for
|
|
interior pointers from one of the thread stacks without
|
|
ALL_INTERIOR_POINTERS. (Thanks to Jeff Sturm.)
|
|
- Added Mingw32 support. (Thanks again to Jeff Sturm for the patch.)
|
|
- Changed the alpha port to use the generic register scanning code instead
|
|
of alpha_mach_dep.s. Alpha_mach_dep.s doesn't look for pointers in fp
|
|
registers, but gcc sometimes spills pointers there. (Thanks to Manuel
|
|
Serrano for helping me debug this by email.) Changed the IA64 code to
|
|
do something similar for similar reasons.
|
|
|
|
Since 5.0alpha6:
|
|
- -DREDIRECT_MALLOC was broken in alpha6. Fixed.
|
|
- Cleaned up gc_ccp.h slightly, thus also causing the HP C++ compiler to
|
|
accept it.
|
|
- Removed accidental reference to dbg_mlc.c, which caused dbg_mlc.o to be
|
|
linked into every executable.
|
|
- Added PREFETCH to bitmap marker. Changed it to use the header cache.
|
|
- GC_push_marked sometimes pushed one object too many, resulting in a
|
|
segmentation fault in GC_mark_from_mark_stack. This was probably an old
|
|
bug. It finally showed up in gctest on win32.
|
|
- Gc_priv.h erroneously #defined GC_incremental to be TRUE instead of FALSE
|
|
when SMALL_CONFIG was defined. This was no doubt a major performance bug for
|
|
the default win32 configuration.
|
|
- Removed -DSMALL_CONFIG from NT_MAKEFILE. It seemed like an anchronism now
|
|
that the average PC has 64MB or so.
|
|
- Integrated Bryce McKinley's patches for linux threads and dynamic loading
|
|
from the libgcj tree. Turned on dynamic loading support for Linux/PPC.
|
|
- Changed the stack finding code to use environ on HP/UX. (Thanks
|
|
to Gustavo Rodriguez-Rivera for the suggestion.) This should probably
|
|
be done on other platforms, too. Since I can't test those, that'll
|
|
wait until after 5.0.
|
|
|
|
Since 5.0alpha7:
|
|
- Fixed threadlibs.c for linux threads. -DUSE_LD_WRAP was broken and
|
|
-ldl was omitted. Fixed Linux stack finding code to handle
|
|
-DUSE_LD_WRAP correctly.
|
|
- Added MSWIN32 exception handler around marker, so that the collector
|
|
can recover from root segments that are unmapped during the collection.
|
|
This caused occasional failures under Windows 98, and may also be
|
|
an issue under Windows NT/2000.
|
|
|
|
To do:
|
|
- Integrate Linux/SPARC fixes.
|
|
- Very large root set sizes (> 16 MB or so) could cause the collector
|
|
to abort with an unexpected mark stack overflow. (Thanks again to
|
|
Peter Chubb.) NOT YET FIXED. Workaround is to increase the initial
|
|
size.
|
|
- The SGI version of the collector marks from mmapped pages, even
|
|
if they are not part of dynamic library static data areas. This
|
|
causes performance problems with some SGI libraries that use mmap
|
|
as a bitmap allocator. NOT YET FIXED. It may be possible to turn
|
|
off DYNAMIC_LOADING in the collector as a workaround. It may also
|
|
be possible to conditionally intercept mmap and use GC_exclude_static_roots.
|
|
The real fix is to walk rld data structures, which looks possible.
|
|
- Integrate MIT and DEC pthreads ports.
|
|
- Incremental collector should handle large objects better. Currently,
|
|
it looks like the whole object is treated as dirty if any part of it
|
|
is.
|
|
- Cord/cordprnt.c doesn't build on a few platforms (notably PowerPC), since
|
|
we make some unwarranted assumptions about how varargs are handled. This
|
|
currently makes the cord-aware versions of printf unusable on some platforms.
|
|
Fixing this is unfortunately not trivial.
|