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nix: Disable GC during coroutine when bdwgc < 8.4

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This re-enables support for older bwdgc versions without complicating
the code too much.
Coroutines generally only interfere with GC during source filtering,
so it's not too bad of a regression on older bdwgc.
This seems preferable over conditional compilation to enable the patch
etc; we've already spent a lot of complexity budget on this GC-coroutine
interaction...
This commit is contained in:
Robert Hensing 2024-03-05 16:39:06 +01:00
parent b311f51f84
commit cc6f315252
2 changed files with 11 additions and 7 deletions
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2
configure.ac
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@ -366,7 +366,7 @@ fi
AC_ARG_ENABLE(gc, AS_HELP_STRING([--enable-gc],[enable garbage collection in the Nix expression evaluator (requires Boehm GC) [default=yes]]),
gc=$enableval, gc=yes)
if test "$gc" = yes; then
PKG_CHECK_MODULES([BDW_GC], [bdw-gc >= 8.2.4])
PKG_CHECK_MODULES([BDW_GC], [bdw-gc])
CXXFLAGS="$BDW_GC_CFLAGS $CXXFLAGS"
AC_DEFINE(HAVE_BOEHMGC, 1, [Whether to use the Boehm garbage collector.])
fi

16
src/libexpr/eval.cc
View file

@ -348,14 +348,14 @@ void initGC()
GC_set_oom_fn(oomHandler);
// TODO: Comment suggests an implementation that works on darwin and windows
// https://github.com/ivmai/bdwgc/issues/362#issuecomment-1936672196
#ifndef __APPLE__
GC_set_sp_corrector(&fixupBoehmStackPointer);
#endif
StackAllocator::defaultAllocator = &boehmGCStackAllocator;
// TODO: Remove __APPLE__ condition.
// Comment suggests an implementation that works on darwin and windows
// https://github.com/ivmai/bdwgc/issues/362#issuecomment-1936672196
#if GC_VERSION_MAJOR >= 8 && GC_VERSION_MINOR >= 4 && !defined(__APPLE__)
GC_set_sp_corrector(&fixupBoehmStackPointer);
if (!GC_get_sp_corrector()) {
printTalkative("BoehmGC on this platform does not support sp_corrector; will disable GC inside coroutines");
/* Used to disable GC when entering coroutines on macOS */
@ -363,6 +363,10 @@ void initGC()
return std::make_shared<BoehmDisableGC>();
};
}
#else
#warning "BoehmGC version does not support GC while coroutine exists. GC will be disabled inside coroutines. Consider updating bwd-gc to 8.4 or later."
#endif
/* Set the initial heap size to something fairly big (25% of
physical RAM, up to a maximum of 384 MiB) so that in most cases