+++ /dev/null
-The collector supports both incremental collection and threads under
-Solaris 2. The incremental collector normally retrieves page dirty information
-through the appropriate /proc calls. But it can also be configured
-(by defining MPROTECT_VDB instead of PROC_VDB in gcconfig.h) to use mprotect
-and signals. This may result in shorter pause times, but it is no longer
-safe to issue arbitrary system calls that write to the heap.
-
-Under other UNIX versions,
-the collector normally obtains memory through sbrk. There is some reason
-to expect that this is not safe if the client program also calls the system
-malloc, or especially realloc. The sbrk man page strongly suggests this is
-not safe: "Many library routines use malloc() internally, so use brk()
-and sbrk() only when you know that malloc() definitely will not be used by
-any library routine." This doesn't make a lot of sense to me, since there
-seems to be no documentation as to which routines can transitively call malloc.
-Nonetheless, under Solaris2, the collector now (since 4.12) allocates
-memory using mmap by default. (It defines USE_MMAP in gcconfig.h.)
-You may want to reverse this decisions if you use -DREDIRECT_MALLOC=...
-
-
-SOLARIS THREADS:
-
-The collector must be compiled with -DGC_SOLARIS_THREADS (thr_ functions)
-or -DGC_SOLARIS_PTHREADS (pthread_ functions) to be thread safe.
-It is also essential that gc.h be included in files that call thr_create,
-thr_join, thr_suspend, thr_continue, or dlopen. Gc.h macro defines
-these to also do GC bookkeeping, etc. Gc.h must be included with
-one or both of these macros defined, otherwise
-these replacements are not visible.
-A collector built in this way way only be used by programs that are
-linked with the threads library.
-
-In this mode, the collector contains various workarounds for older Solaris
-bugs. Mostly, these should not be noticeable unless you look at system
-call traces. However, it cannot protect a guard page at the end of
-a thread stack. If you know that you will only be running Solaris2.5
-or later, it should be possible to fix this by compiling the collector
-with -DSOLARIS23_MPROTECT_BUG_FIXED.
-
-Since 5.0 alpha5, dlopen disables collection temporarily,
-unless USE_PROC_FOR_LIBRARIES is defined. In some unlikely cases, this
-can result in unpleasant heap growth. But it seems better than the
-race/deadlock issues we had before.
-
-If solaris_threads are used on an X86 processor with malloc redirected to
-GC_malloc, it is necessary to call GC_thr_init explicitly before forking the
-first thread. (This avoids a deadlock arising from calling GC_thr_init
-with the allocation lock held.)
-
-It appears that there is a problem in using gc_cpp.h in conjunction with
-Solaris threads and Sun's C++ runtime. Apparently the overloaded new operator
-is invoked by some iostream initialization code before threads are correctly
-initialized. As a result, call to thr_self() in garbage collector
-initialization segfaults. Currently the only known workaround is to not
-invoke the garbage collector from a user defined global operator new, or to
-have it invoke the garbage-collector's allocators only after main has started.
-(Note that the latter requires a moderately expensive test in operator
-delete.)
-
-Hans-J. Boehm
-(The above contains my personal opinions, which are probably not shared
-by anyone else.)
projects / msp430-gcc.git / blobdiff