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Diffstat (limited to 'boehm-gc/doc/README.darwin')
| -rw-r--r-- | boehm-gc/doc/README.darwin | 34 |
1 files changed, 28 insertions, 6 deletions
diff --git a/boehm-gc/doc/README.darwin b/boehm-gc/doc/README.darwin index 3cd1b818b19..72d60406d5c 100644 --- a/boehm-gc/doc/README.darwin +++ b/boehm-gc/doc/README.darwin @@ -1,5 +1,5 @@ -Darwin/MacOSX Support - July 22, 2003 -==================================== +Darwin/MacOSX Support - December 16, 2003 +========================================= Important Usage Notes ===================== @@ -15,7 +15,7 @@ run and perhaps called GC_malloc(), create an initialization routine for each library to call GC_init(): #include <gc/gc.h> -void my_library_init() { GC_init(); } +extern "C" void my_library_init() { GC_init(); } Compile this code into a my_library_init.o, and link it into your dylib. When you link the dylib, pass the -init argument with @@ -34,6 +34,12 @@ work reliably with workarounds for a few possible bugs in place however these workaround may not work correctly in all cases. There may also be additional problems that I have not found. +Thread-local GC allocation will not work with threads that are not +created using the GC-provided override of pthread_create(). Threads +created without the GC-provided pthread_create() do not have the +necessary data structures in the GC to store this data. + + Implementation Information ========================== Darwin/MacOSX support is nearly complete. Thread support is reliable on @@ -42,11 +48,27 @@ Darwin versions (MacOSX 10.1). Shared library support had also been added and the gc can be run from a shared library. There is currently only support for Darwin/PPC although adding x86 support should be trivial. -Thread support is implemented in terms of mach thread_suspend and +Thread support is implemented in terms of mach thread_suspend and thread_resume calls. These provide a very clean interface to thread suspension. This implementation doesn't rely on pthread_kill so the -code works on Darwin < 6.0 (MacOSX 10.1). All the code to stop the -world is located in darwin_stop_world.c. +code works on Darwin < 6.0 (MacOSX 10.1). All the code to stop and +start the world is located in darwin_stop_world.c. + +Since not all uses of the GC enable clients to override pthread_create() +before threads have been created, the code for stopping the world has +been rewritten to look for threads using Mach kernel calls. Each +thread identified in this way is suspended and resumed as above. In +addition, since Mach kernel threads do not contain pointers to their +stacks, a stack-walking function has been written to find the stack +limits. Given an initial stack pointer (for the current thread, a +pointer to a stack-allocated local variable will do; for a non-active +thread, we grab the value of register 1 (on PowerPC)), it +will walk the PPC Mach-O-ABI compliant stack chain until it reaches the +top of the stack. This appears to work correctly for GCC-compiled C, +C++, Objective-C, and Objective-C++ code, as well as for Java +programs that use JNI. If you run code that does not follow the stack +layout or stack pointer conventions laid out in the PPC Mach-O ABI, +then this will likely crash the garbage collector. The original incremental collector support unfortunatelly no longer works on recent Darwin versions. It also relied on some undocumented kernel |