157 lines
7.3 KiB
Plaintext
157 lines
7.3 KiB
Plaintext
The collector has at various times been compiled under Windows 95 & NT,
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with the original Microsoft SDK, with Visual C++ 2.0, 4.0, and 6, with
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the GNU win32 environment, with Borland 4.5, with Watcom C, and recently
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with the Digital Mars compiler. It is likely that some of these have been
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broken in the meantime. Patches are appreciated.
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It runs under both win32s and win32, but with different semantics.
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Under win32, all writable pages outside of the heaps and stack are
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scanned for roots. Thus the collector sees pointers in DLL data
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segments. Under win32s, only the main data segment is scanned.
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(The main data segment should always be scanned. Under some
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versions of win32s, other regions may also be scanned.)
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Thus all accessible objects should be accessible from local variables
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or variables in the main data segment. Alternatively, other data
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segments (e.g. in DLLs) may be registered with the collector by
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calling GC_init() and then GC_register_root_section(a), where
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a is the address of some variable inside the data segment. (Duplicate
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registrations are ignored, but not terribly quickly.)
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(There are two reasons for this. We didn't want to see many 16:16
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pointers. And the VirtualQuery call has different semantics under
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the two systems, and under different versions of win32s.)
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The collector test program "gctest" is linked as a GUI application,
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but does not open any windows. Its output appears in the file
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"gc.log". It may be started from the file manager. The hour glass
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cursor may appear as long as it's running. If it is started from the
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command line, it will usually run in the background. Wait a few
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minutes (a few seconds on a modern machine) before you check the output.
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You should see either a failure indication or a "Collector appears to
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work" message.
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The cord test program has not been ported (but should port
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easily). A toy editor (cord/de.exe) based on cords (heavyweight
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strings represented as trees) has been ported and is included.
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It runs fine under either win32 or win32S. It serves as an example
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of a true Windows application, except that it was written by a
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nonexpert Windows programmer. (There are some peculiarities
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in the way files are displayed. The <cr> is displayed explicitly
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for standard DOS text files. As in the UNIX version, control
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characters are displayed explicitly, but in this case as red text.
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This may be suboptimal for some tastes and/or sets of default
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window colors.)
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In general -DREDIRECT_MALLOC is unlikely to work unless the
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application is completely statically linked.
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The collector normally allocates memory from the OS with VirtualAlloc.
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This appears to cause problems under Windows NT and Windows 2000 (but
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not Windows 95/98) if the memory is later passed to CreateDIBitmap.
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To work around this problem, build the collector with -DUSE_GLOBAL_ALLOC.
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This is currently incompatible with -DUSE_MUNMAP. (Thanks to Jonathan
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Clark for tracking this down.)
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For Microsoft development tools, rename NT_MAKEFILE as
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MAKEFILE. (Make sure that the CPU environment variable is defined
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to be i386.) In order to use the gc_cpp.h C++ interface, all
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client code should include gc_cpp.h.
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Clients may need to define GC_NOT_DLL before including gc.h, if the
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collector was built as a static library (as it normally is in the
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absence of thread support).
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For GNU-win32, use the regular makefile, possibly after uncommenting
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the line "include Makefile.DLLs". The latter should be necessary only
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if you want to package the collector as a DLL. The GNU-win32 port is
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believed to work only for b18, not b19, probably dues to linker changes
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in b19. This is probably fixable with a different definition of
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DATASTART and DATAEND in gcconfig.h.
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For Borland tools, use BCC_MAKEFILE. Note that
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Borland's compiler defaults to 1 byte alignment in structures (-a1),
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whereas Visual C++ appears to default to 8 byte alignment (/Zp8).
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The garbage collector in its default configuration EXPECTS AT
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LEAST 4 BYTE ALIGNMENT. Thus the BORLAND DEFAULT MUST
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BE OVERRIDDEN. (In my opinion, it should usually be anyway.
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I expect that -a1 introduces major performance penalties on a
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486 or Pentium.) Note that this changes structure layouts. (As a last
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resort, gcconfig.h can be changed to allow 1 byte alignment. But
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this has significant negative performance implications.)
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The Makefile is set up to assume Borland 4.5. If you have another
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version, change the line near the top. By default, it does not
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require the assembler. If you do have the assembler, I recommend
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removing the -DUSE_GENERIC.
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There is some support for incremental collection. This is
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currently pretty simple-minded. Pages are protected. Protection
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faults are caught by a handler installed at the bottom of the handler
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stack. This is both slow and interacts poorly with a debugger.
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Whenever possible, I recommend adding a call to
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GC_enable_incremental at the last possible moment, after most
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debugging is complete. Unlike the UNIX versions, no system
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calls are wrapped by the collector itself. It may be necessary
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to wrap ReadFile calls that use a buffer in the heap, so that the
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call does not encounter a protection fault while it's running.
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(As usual, none of this is an issue unless GC_enable_incremental
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is called.)
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Note that incremental collection is disabled with -DSMALL_CONFIG.
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James Clark has contributed the necessary code to support win32 threads.
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Use NT_THREADS_MAKEFILE (a.k.a gc.mak) instead of NT_MAKEFILE
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to build this version. Note that this requires some files whose names
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are more than 8 + 3 characters long. Thus you should unpack the tar file
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so that long file names are preserved. To build the garbage collector
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test with VC++ from the command line, use
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nmake /F ".\gc.mak" CFG="gctest - Win32 Release"
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This requires that the subdirectory gctest\Release exist.
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The test program and DLL will reside in the Release directory.
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This version relies on the collector residing in a dll.
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This version currently supports incremental collection only if it is
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enabled before any additional threads are created.
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Version 4.13 attempts to fix some of the earlier problems, but there
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may be other issues. If you need solid support for win32 threads, you
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might check with Geodesic Systems. Their collector must be licensed,
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but they have invested far more time in win32-specific issues.
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Hans
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Ivan V. Demakov's README for the Watcom port:
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The collector has been compiled with Watcom C 10.6 and 11.0.
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It runs under win32, win32s, and even under msdos with dos4gw
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dos-extender. It should also run under OS/2, though this isn't
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tested. Under win32 the collector can be built either as dll
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or as static library.
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Note that all compilations were done under Windows 95 or NT.
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For unknown reason compiling under Windows 3.11 for NT (one
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attempt has been made) leads to broken executables.
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Incremental collection is not supported.
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cord is not ported.
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Before compiling you may need to edit WCC_MAKEFILE to set target
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platform, library type (dynamic or static), calling conventions, and
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optimization options.
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To compile the collector and testing programs use the command:
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wmake -f WCC_MAKEFILE
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All programs using gc should be compiled with 4-byte alignment.
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For further explanations on this see comments about Borland.
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If gc compiled as dll, the macro ``GC_DLL'' should be defined before
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including "gc.h" (for example, with -DGC_DLL compiler option). It's
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important, otherwise resulting programs will not run.
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Ivan Demakov (email: ivan@tgrad.nsk.su)
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