Copyright (c) 1996-1999 by Silicon Graphics. All rights reserved.
Copyright (c) 1999 by Hewlett-Packard Company. All rights reserved.
- [ This version of the collector modified by Cygnus Solutions.
+ [ This version of the collector modified for use in libgcj.
See the file ChangeLog for details ]
THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
provided the above notices are retained, and a notice that the code was
modified is included with the above copyright notice.
-This is version 5.0alpha4 of a conservative garbage collector for C and C++.
+This is version 5.0 of a conservative garbage collector for C and C++.
You might find a more recent version of this at
Early versions of this collector were developed as a part of research
projects supported in part by the National Science Foundation
and the Defense Advance Research Projects Agency.
-Much of the code was rewritten by Hans-J. Boehm (boehm@acm.org) at Xerox PARC
-and at SGI.
+Much of the code was rewritten by Hans-J. Boehm (boehm@acm.org) at Xerox PARC,
+SGI, and HP Labs.
Some other contributors:
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 chnging it
+ - 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.
- 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
- 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.
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