Commit Graph

314 Commits

Author SHA1 Message Date
Ian Lance Taylor
4a2bb7fcb0 compiler, runtime: replace hashmap code with Go 1.7 hashmap
This change removes the gccgo-specific hashmap code and replaces it with
    the hashmap code from the Go 1.7 runtime.  The Go 1.7 hashmap code is
    more efficient, does a better job on details like when to update a key,
    and provides some support against denial-of-service attacks.
    
    The compiler is changed to call the new hashmap functions instead of the
    old ones.
    
    The compiler now tracks which types are reflexive and which require
    updating when used as a map key, and records the information in map type
    descriptors.
    
    Map_index_expression is simplified.  The special case for a map index on
    the right hand side of a tuple expression has been unnecessary for some
    time, and is removed.  The support for specially marking a map index as
    an lvalue is removed, in favor of lowering an assignment to a map index
    into a function call.  The long-obsolete support for a map index of a
    pointer to a map is removed.
    
    The __go_new_map_big function (known to the compiler as
    Runtime::MAKEMAPBIG) is no longer needed, as the new runtime.makemap
    function takes an int64 hint argument.
    
    The old map descriptor type and supporting expression is removed.
    
    The compiler was still supporting the long-obsolete syntax `m[k] = 0,
    false` to delete a value from a map.  That is now removed, requiring a
    change to one of the gccgo-specific tests.
    
    The builtin len function applied to a map or channel p is now compiled
    as `p == nil ? 0 : *(*int)(p)`.  The __go_chan_len function (known to
    the compiler as Runtime::CHAN_LEN) is removed.
    
    Support for a shared zero value for maps to large value types is
    introduced, along the lines of the gc compiler.  The zero value is
    handled as a common variable.
    
    The hash function is changed to take a seed argument, changing the
    runtime hash functions and the compiler-generated hash functions.
    Unlike the gc compiler, both the hash and equal functions continue to
    take the type length.
    
    Types that can not be compared now store nil for the hash and equal
    functions, rather than pointing to functions that throw.  Interface hash
    and comparison functions now check explicitly for nil.  This matches the
    gc compiler and permits a simple implementation for ismapkey.
    
    The compiler is changed to permit marking struct and array types as
    incomparable, meaning that they have no hash or equal function.  We use
    this for thunk types, removing the existing special code to avoid
    generating hash/equal functions for them.
    
    The C runtime code adds memclr, memequal, and memmove functions.
    
    The hashmap code uses go:linkname comments to make the functions
    visible, as otherwise the compiler would discard them.
    
    The hashmap code comments out the unused reference to the address of the
    first parameter in the race code, as otherwise the compiler thinks that
    the parameter escapes and copies it onto the heap.  This is probably not
    needed when we enable escape analysis.
    
    Several runtime map tests that ere previously skipped for gccgo are now
    run.
    
    The Go runtime picks up type kind information and stubs.  The type kind
    information causes the generated runtime header file to define some
    constants, including `empty`, and the C code is adjusted accordingly.
    
    A Go-callable version of runtime.throw, that takes a Go string, is
    added to be called from the hashmap code.
    
    Reviewed-on: https://go-review.googlesource.com/29447

	* go.go-torture/execute/map-1.go: Replace old map deletion syntax
	with call to builtin delete function.

From-SVN: r240334
2016-09-21 20:58:51 +00:00
Ian Lance Taylor
b276eda4b4 re PR go/77642 (GO Bootstrap fail starting with r239872 splitstack signature does not match)
PR go/77642

    runtime: pass correct type to __splitstack_find
    
    The code was passing uintptr* to a function that expected size_t*.
    
    Based on patch by Andreas Krebbel.
    
    Fixes GCC PR 77642.
    
    Reviewed-on: https://go-review.googlesource.com/29433

From-SVN: r240275
2016-09-20 16:48:19 +00:00
Ian Lance Taylor
ac376b15df runtime: use alignof to check alignment of ucontext_t
Use alignof rather than assuming a 16 byte alignment.
    
    Reviewed-on: https://go-review.googlesource.com/28913

From-SVN: r240047
2016-09-09 16:39:44 +00:00
Ian Lance Taylor
a9ca0a9d02 runtime: remove remaining use of MAKECONTEXT_STACK_TOP macro
The definition and most uses of MAKECONTEXT_STACK_TOP were removed in
    https://golang.org/cl/88660043, which removed support for Solaris 8/9.
    One use of MAKECONTEXT_STACK_TOP was accidentally left in the source
    code.  Remove it now.
    
    Reviewed-on: https://go-review.googlesource.com/28911

From-SVN: r240045
2016-09-09 14:00:43 +00:00
Ian Lance Taylor
6f02c13813 runtime: align ucontext_t argument to 16 byte boundary
Some systems, such as ia64 and PPC, require that a ucontext_t pointer
    passed to getcontext and friends be aligned to a 16-byte boundary.
    Currently the ucontext_t fields in the g structure are defined in Go,
    and Go has no way to ensure a 16-byte alignment for a struct field.
    The fields are currently represented by an array of unsafe.Pointer.
    Enforce the alignment by making the array larger, and picking an offset
    into the array that is 16-byte aligned.
    
    Reviewed-on: https://go-review.googlesource.com/28910

From-SVN: r240044
2016-09-09 13:31:49 +00:00
Ian Lance Taylor
fc4eaccf10 runtime: make gsignal stack at least SIGSTKSZ bytes
The default stack size for the gsignal goroutine, 32K, is not enough on
    ia64.  Make sure that the stack size is at least SIGSTKSZ.
    
    Reviewed-on: https://go-review.googlesource.com/28224

From-SVN: r239894
2016-08-31 13:59:03 +00:00
Ian Lance Taylor
75791bab05 runtime: use -fgo-c-header to build C header file
Use the new -fgo-c-header option to build a header file for the Go
    runtime code in libgo/go/runtime, and use the new header file in the C
    runtime code in libgo/runtime.  This will ensure that the Go code and C
    code share the same data structures as we convert the runtime from C to
    Go.
    
    The new file libgo/go/runtime/runtime2.go is copied from the Go 1.7
    release, and then edited to remove unnecessary data structures and
    modify others for use with libgo.
    
    The new file libgo/go/runtime/mcache.go is an initial version of the
    same files in the Go 1.7 release, and will be replaced by the Go 1.7
    file when we convert to the new memory allocator.
    
    The new file libgo/go/runtime/type.go describes the gccgo version of the
    reflection data structures, and replaces the Go 1.7 runtime file which
    describes the gc version of those structures.
    
    Using the new header file means changing a number of struct fields to
    use Go naming conventions (that is, no underscores) and to rename
    constants to have a leading underscore so that they are not exported
    from the Go package.  These names were updated in the C code.
    
    The C code was also changed to drop the thread-local variable m, as was
    done some time ago in the gc sources.  Now the m field is always
    accessed using g->m, where g is the single remaining thread-local
    variable.  This in turn required some adjustments to set g->m correctly
    in all cases.
    
    Also pass the new -fgo-compiling-runtime option when compiling the
    runtime package, although that option doesn't do anything yet.
    
    Reviewed-on: https://go-review.googlesource.com/28051

From-SVN: r239872
2016-08-30 21:07:47 +00:00
Ian Lance Taylor
f432d1282d re PR go/72814 (reflect FAILs on 32-bit Solaris/SPARC: SIGILL)
PR go/72814

    runtime: treat zero-sized result value as void
    
    Change the FFI interface to treat a call to a function that returns a
    zero-sized result as a call to a function that returns void.
    
    This is part of the fix for https://gcc.gnu.org/PR72814.  On 32-bit
    SPARC systems, a call to a function that returns a non-zero-sized struct
    is followed by an unimp instruction that describes the size of the
    struct.  The function returns to the address after the unimp
    instruction.  The libffi library can not represent a zero-sized struct,
    so we wind up treating it as a 1-byte struct.  Thus in that case libffi
    calls the function with an unimp instruction, but the function does not
    adjust the return address.  The result is that the program attempts to
    execute the unimp instruction, causing a crash.
    
    This is part of a change that fixes the crash by treating all functions
    that return zero bytes as functions that return void.
    
    Reviewed-on: https://go-review.googlesource.com/25585

	* go-gcc.cc (Gcc_backend::function_type): If the return type is
	zero bytes, treat the function as returning void.
	(return_statement): If the return type is zero bytes, don't
	actually return any values.

From-SVN: r239252
2016-08-08 19:53:44 +00:00
Ian Lance Taylor
e0f69f36ea libgo: change build procedure to use build tags
Previously the libgo Makefile explicitly listed the set of files to
    compile for each package.  For packages that use build tags, this
    required a lot of awkward automake conditionals in the Makefile.
    
    This CL changes the build to look at the build tags in the files.
    The new shell script libgo/match.sh does the matching.  This required
    adjusting a lot of build tags, and removing some files that are never
    used.  I verified that the exact same sets of files are compiled on
    amd64 GNU/Linux.  I also tested the build on i386 Solaris.
    
    Writing match.sh revealed some bugs in the build tag handling that
    already exists, in a slightly different form, in the gotest shell
    script.  This CL fixes those problems as well.
    
    The old code used automake conditionals to handle systems that were
    missing strerror_r and wait4.  Rather than deal with those in Go, those
    functions are now implemented in runtime/go-nosys.c when necessary, so
    the Go code can simply assume that they exist.
    
    The os testsuite looked for dir_unix.go, which was never built for gccgo
    and has now been removed.  I changed the testsuite to look for dir.go
    instead.
    
    Reviewed-on: https://go-review.googlesource.com/25546

From-SVN: r239189
2016-08-06 00:36:33 +00:00
Ian Lance Taylor
e91f59b919 runtime: fix incorrectly commented out code in heapdump.c
Reviewed-on: https://go-review.googlesource.com/25490

From-SVN: r239144
2016-08-04 17:21:23 +00:00
Ian Lance Taylor
22b955cca5 libgo: update to go1.7rc3
Reviewed-on: https://go-review.googlesource.com/25150

From-SVN: r238662
2016-07-22 18:15:38 +00:00
Ian Lance Taylor
bb72703282 runtime: Use atomic load for in entersyscall.
Reportedly fixes PPC64 deadlock.
    
    From a comment by Gabriel Russell.
    
    Fixes golang/go#15051.
    
    Reviewed-on: https://go-review.googlesource.com/21450

From-SVN: r234694
2016-04-02 00:47:53 +00:00
Ian Lance Taylor
4501d9ad44 runtime: lock M during cgo call
cgo should lock the M.
    
    
    See also https://golang.org/cl/18882 .
    
    Reviewed-on: https://go-review.googlesource.com/18883

From-SVN: r233670
2016-02-24 15:03:04 +00:00
Ian Lance Taylor
43414a5dd3 libgo: Update to final Go 1.6 release.
Reviewed-on: https://go-review.googlesource.com/19592

From-SVN: r233515
2016-02-18 05:56:46 +00:00
Ian Lance Taylor
54c9c975f1 runtime: For c-archive/c-shared, install signal handlers synchronously.
This is a port of https://golang.org/cl/18150 to the gccgo runtime.
    
    The previous behaviour of installing the signal handlers in a separate
    thread meant that Go initialization raced with non-Go initialization if
    the non-Go initialization also wanted to install signal handlers.  Make
    installing signal handlers synchronous so that the process-wide behavior
    is predictable.
    
    Reviewed-on: https://go-review.googlesource.com/19494

From-SVN: r233393
2016-02-12 22:10:09 +00:00
Ian Lance Taylor
de24ed7803 re PR go/69511 (G.gcstack_size uses uintptr instead of size_t)
PR go/69511
    runtime: change G gcstack_size field to size_t
    
    Because its address is passed to __splitstack_find, which expects size_t*.
    
    From Dominik Vogt in GCC PR 69511.
    
    Reviewed-on: https://go-review.googlesource.com/19429

From-SVN: r233260
2016-02-10 02:16:04 +00:00
Ian Lance Taylor
cc240aa7d1 re PR go/69357 (libgo refers to _end in a non-weak way)
PR go/69537
    runtime: Don't refer to _end symbol in shared library.
    
    Fixes GCC PR 69357.
    
    Reviewed-on: https://go-review.googlesource.com/19362

From-SVN: r233235
2016-02-09 00:34:55 +00:00
Ian Lance Taylor
f98dd1a338 libgo: Update to go1.6rc1.
Reviewed-on: https://go-review.googlesource.com/19200

From-SVN: r233110
2016-02-03 21:58:02 +00:00
Ian Lance Taylor
06caa02ccf compiler, runtime: mark stub methods, ignore them in runtime.Caller.
This fixes the long-standing bug in which the testing package misreports
    the file/line of an error.
    
    Reviewed-on: https://go-review.googlesource.com/19179

From-SVN: r233098
2016-02-03 06:54:41 +00:00
Ian Lance Taylor
ae026741df re PR go/61303 (gccgo: segfault, regression since 4.8.2)
PR go/61303
    runtime: don't overallocate in select code
    
    If we've already allocated an fd_set, don't allocate another one.
    
    Also, don't bother to read from rdwake if it wasn't returned in select.
    
    Fixes https://gcc.gnu.org/PR61303.
    
    Reviewed-on: https://go-review.googlesource.com/17243

From-SVN: r230922
2015-11-26 00:24:21 +00:00
Ian Lance Taylor
8c61286797 re PR go/68496 ([libgo] reflect test fails on Linux x86-64)
PR go/68496
    reflect: Allocate space for FFI functions returning a zero-sized type.
    
    The libffi library does not understand zero-sized types.  We represent
    them as a struct with a single field of type void.  If such a type is
    returned from a function, libffi will copy 1 byte of data.  Allocate
    space for that byte, although we won't use it.
    
    Fixes https://gcc.gnu.org/PR68496.

    Reviewed-on: https://go-review.googlesource.com/17175

From-SVN: r230776
2015-11-23 21:17:45 +00:00
Ian Lance Taylor
bbbe8b338b re PR go/66574 (Time is provided in millisecond precision instead of nanoseconds as described in go documentation)
PR go/66574
    runtime: Use clock_gettime to get current time.
    
    Fetch the current time in nanoseconds, not microseconds, by using
    clock_gettime rather than gettimeofday.
    
    Update golang/go#11222.
    
    Fixes https://gcc.gnu.org/PR66574.
    
    Reviewed-on: https://go-review.googlesource.com/17156

From-SVN: r230694
2015-11-21 01:27:44 +00:00
Ian Lance Taylor
9da92cbda9 libgo: Solaris portability fixes.
Only build net/hook_cloexec.go on GNU/Linux and FreeBSD, because those
    are the only systems with accept4.
    
    Add syscall/libcall_bsd.go to define sendfile for *BSD and Solaris.
    
    Revert tcpsockopt_solaris.go back to the earlier version, so that it
    works on Solaris 10.
    
    Always pass the address of a Pid_t value to TIOCGPGRP and TIOCSPGRP.
    
    Include <unistd.h> in runtime/go-varargs.c.
    
    Reviewed-on: https://go-review.googlesource.com/16719

From-SVN: r229880
2015-11-06 19:15:45 +00:00
Ian Lance Taylor
2b193803d7 runtime: If no split stacks, allocate stacks using mmap on 64-bit systems.
When not using split stacks, libgo allocate large stacks for each
    goroutine.  On a 64-bit system, libgo allocates a maximum of 128G for
    the Go heap, and allocates 4M for each stack.  When the stacks are
    allocated from the Go heap, the result is that a program can only create
    32K goroutines, which is not enough for an active Go server.  This patch
    changes libgo to allocate the stacks using mmap directly, rather than
    allocating them out of the Go heap.  This change is only done for 64-bit
    systems when not using split stacks.  When using split stacks, the
    stacks are allocated using mmap directly anyhow.  On a 32-bit system,
    there is no maximum size for the Go heap, or, rather, the maximum size
    is the available address space anyhow.
    
    Reviewed-on: https://go-review.googlesource.com/16531

From-SVN: r229636
2015-10-31 23:48:19 +00:00
Ian Lance Taylor
af146490bb runtime: Remove now unnecessary pad field from ParFor.
It is not needed due to the removal of the ctx field.
    
    Reviewed-on: https://go-review.googlesource.com/16525

From-SVN: r229616
2015-10-31 00:59:47 +00:00
Ian Lance Taylor
f4a513a98e compiler, reflect, runtime: remove zero field from type descriptor
Type descriptors picked up a zero field because the gc map
    implementation used it.  However, it's since been dropped by the gc
    library.  It was never used by gccgo.  Drop it now in preparation for
    upgrading to the Go 1.5 library.
    
    Reviewed-on: https://go-review.googlesource.com/16486

From-SVN: r229546
2015-10-29 18:14:50 +00:00
Ian Lance Taylor
730f6d1425 compiler, runtime: change type hash/equal to Go funcs
Change the type descriptor hash and equal functions from C code pointers
    to Go func values.  This permits them to be set to a Go function
    closure.  This is in preparation for the Go 1.5, so that we can use a
    closure for the hash/equal functions returned by the new reflect.ArrayOf
    function.
    
    Reviewed-on: https://go-review.googlesource.com/16485

From-SVN: r229541
2015-10-29 17:14:51 +00:00
Ian Lance Taylor
0786e1fe86 re PR go/67874 (fd_unix.go does not build when there is fcntl64 and no fcntl syscall)
PR go/67874
    net, runtime: Call C library fcntl function rather than syscall.Syscall.
    
    Not all systems define a fcntl syscall; some only have fcntl64.
    
    Fixes GCC PR go/67874.
    
    Reviewed-on: https://go-review.googlesource.com/15497

From-SVN: r228576
2015-10-07 17:22:08 +00:00
Ian Lance Taylor
055db850c6 runtime: Fix recent lfstack change on Solaris.
Reviewed-on: https://go-review.googlesource.com/14922

From-SVN: r228087
2015-09-24 13:33:20 +00:00
Ian Lance Taylor
46efdbbc01 runtime: rewrite lfstack packing/unpacking to look more like that in Go
Reviewed-on: https://go-review.googlesource.com/13037

From-SVN: r228057
2015-09-23 17:07:15 +00:00
Ian Lance Taylor
7e56d66864 runtime: Ignore stack sizes when deciding when to GC.
This restores https://golang.org/cl/6081043 which was lost accidentally
    when updating a new version of libgo in https://golang.org/cl/22440043 .
    
    Reviewed-on: https://go-review.googlesource.com/14569

From-SVN: r227784
2015-09-15 12:32:31 +00:00
Ian Lance Taylor
5dbd3b8045 libgo/runtime: return 0, not NULL, from main
Reviewed-on: https://go-review.googlesource.com/13421

From-SVN: r227673
2015-09-11 03:12:28 +00:00
Ian Lance Taylor
f48495834f runtime: initialize variable to avoid compiler warning
Reviewed-on: https://go-review.googlesource.com/13095

From-SVN: r226543
2015-08-04 03:39:21 +00:00
Ian Lance Taylor
3d6d2a63b2 re PR go/67101 (mprof.goc:408:5: error: calling ‘__builtin_frame_address’ with a nonzero argument is unsafe [-Werror=frame-address])
PR go/67101

    runtime: Remove call to __builtin_frame_address.
    
    __builtin_frame_address was only supposed to use nonzero arguments
    for debugging purposes.  Calling it with nonzero arguments can have
    unpredictable results and uses are now marked unsafe when
    -Wframe-address is enabled.
    
    Reviewed-on: https://go-review.googlesource.com/13063

From-SVN: r226525
2015-08-03 17:54:50 +00:00
Ian Lance Taylor
67a546ab45 compiler,runtime: Determine if allocations need new pointers in runtime.
As the removed comment states, if the package being compiled played
    certain tricks with pointers that looked like integers, the compiler
    might allocate space for new pointers unnecessarily.  Since the type
    information on the heap is now precise, this logic can be moved to the
    runtime.
    
    Reviewed-on: https://go-review.googlesource.com/11581

From-SVN: r225757
2015-07-14 01:22:25 +00:00
Ian Lance Taylor
5ea73ae3b8 libgo: Use __USING_SJLJ_EXCEPTIONS__ rather than configure test.
From Eric Botcazou.

From-SVN: r223231
2015-05-16 00:17:46 +00:00
Ian Lance Taylor
b1b0e90567 runtime: Fix runtime/pprof test when libgo is not optimized.
When libgo is not optimized the static function profilealloc
in malloc.goc shows up in the stack trace.  Rename it to
runtime_profilealloc so that runtime/pprof.printStackRecord
ignores it.

From-SVN: r223006
2015-05-11 16:19:23 +00:00
Ian Lance Taylor
bd9e8f7e4a re PR go/66016 (Accessing nil Func's name results in crash)
PR go/66016
runtime: Don't crash in Func.Name if the Func is nil.

Related to Go issue 10696

From-SVN: r222816
2015-05-05 16:38:57 +00:00
Ian Lance Taylor
081564faed runtime: Support -buildmode=c-shared.
These changes permit using the go tool from the upcoming Go
1.5 release with -buildmode=c-archive to build gccgo code into
an archive file that can be linked with a C program.

From-SVN: r222594
2015-04-29 21:31:53 +00:00
Ian Lance Taylor
46f120ca7b re PR go/65798 (runtime.Caller returns ok=true when return data is invalid)
PR go/65798
runtime: In Caller don't return ok == true if PC == 0.

GCC PR 65798 reports that this can happen in some cases.

From-SVN: r222204
2015-04-17 21:59:10 +00:00
Ian Lance Taylor
5fdb119fd5 re PR go/64999 (s390x libgo test failure in TestMemoryProfiler)
PR go/64999
	PR go/65180
runtime: Adjust libbacktrace PC value to what runtime.Callers expects.

From Lynn Boger.

From-SVN: r222196
2015-04-17 19:29:28 +00:00
Ian Lance Taylor
90e00f872d re PR go/65755 (incorrect reflection of struct fields with gccgo)
PR go/65755
compiler, runtime, reflect: Use reflection string for type comparisons.

Change the runtime and reflect libraries to always use only
the type reflection string to determine whether two types are
equal.  It previously used the PkgPath and Name values for a
type name, but that required a PkgPath that did not match the
gc compiler.

Change the compiler to use the same PkgPath value as the gc
compiler in all cases.

Change the compiler to put the receiver type in the reflection
string for a type defined inside a method.

From-SVN: r222194
2015-04-17 18:19:44 +00:00
Ian Lance Taylor
2ee920291d Remove some files that were accidentally committed in 2014.
From-SVN: r221802
2015-03-31 19:47:23 +00:00
Ian Lance Taylor
dc4d494ae9 re PR go/65349 (go tool crashes, can't compile go code on 32bit linux systems)
PR go/65349
runtime: Don't crash if explicitly freeing small map.

From-SVN: r221292
2015-03-09 23:43:16 +00:00
Ian Lance Taylor
4729d7726b re PR go/65349 (go tool crashes, can't compile go code on 32bit linux systems)
PR go/65349
runtime: Don't call malloc from __go_file_line callback.

When crashing, we call runtime_printcreatedby which calls
__go_file_line which used to call the Go malloc.  If we are
crashing due to a signal due to heap corruption of some sort,
the GO malloc lock might already be held, leading to a crash
within a crash.  Avoid that by assuming that the libbacktrace
strings will stick around, as we already do in go-callers.c.

From-SVN: r221291
2015-03-09 23:40:58 +00:00
Ian Lance Taylor
8c5c44aa7e runtime: Add memprofilerate to GODEBUG
Add memprofilerate as a value recognized
in the GODEBUG env var.  The value provided
is used as the new setting for
runtime.MemProfileRate, allowing the user
to adjust memory profiling.

From-SVN: r220470
2015-02-06 05:03:22 +00:00
Ian Lance Taylor
e0a0c2f4c6 re PR go/64595 (go programs abort when debug info is stripped)
PR go/64595
runtime: Don't crash in runtime_callers if no debug info available.

From-SVN: r220057
2015-01-23 19:49:53 +00:00
Ian Lance Taylor
cea526b81c runtime: No special case for 386 complex in FFI support.
All supported libgo 386 targets now have complex support in
libffi.

From Uros Bizjak.

From-SVN: r219877
2015-01-20 04:18:12 +00:00
Ian Lance Taylor
0f59f5c120 runtime: Add __sparc__ case for SETCONTEXT_CLOBBERS_TLS.
The glibc setcontext incorrectly modifies %g7 on SPARC.

From Richard Henderson.

From-SVN: r219778
2015-01-16 23:23:31 +00:00
Richard Henderson
38bf819a5f compiler, reflect, runtime: Use static chain for closures.
Change from using __go_set_closure to passing the closure
value in the static chain field.  Uses new backend support for
setting the closure chain in a call from C via
__builtin_call_with_static_chain.  Uses new support in libffi
for Go closures.

The old architecture specific support for reflect.MakeFunc is
removed, replaced by the libffi support.

All work done by Richard Henderson.

	* go-gcc.cc (Gcc_backend::call_expression): Add chain_expr argument.
	(Gcc_backend::static_chain_variable): New method.

From-SVN: r219776
2015-01-16 22:58:53 +00:00