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Merge pull request #4206 from hercules-ci/fix-coroutine-gc

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Fix memory corruption caused by GC-invisible coroutine stacks
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Eelco Dolstra 2020-11-05 10:18:31 +01:00 • committed by GitHub
commit 387f824cab
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4 changed files with 80 additions and 2 deletions
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31
src/libexpr/eval.cc
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@ -27,6 +27,10 @@
#include <gc/gc.h>
#include <gc/gc_cpp.h>
#include <boost/coroutine2/coroutine.hpp>
#include <boost/coroutine2/protected_fixedsize_stack.hpp>
#include <boost/context/stack_context.hpp>
#endif
namespace nix {
@ -220,6 +224,31 @@ static void * oomHandler(size_t requested)
/* Convert this to a proper C++ exception. */
throw std::bad_alloc();
}
class BoehmGCStackAllocator : public StackAllocator {
boost::coroutines2::protected_fixedsize_stack stack {
// We allocate 8 MB, the default max stack size on NixOS.
// A smaller stack might be quicker to allocate but reduces the stack
// depth available for source filter expressions etc.
std::max(boost::context::stack_traits::default_size(), static_cast<std::size_t>(8 * 1024 * 1024))
};
public:
boost::context::stack_context allocate() override {
auto sctx = stack.allocate();
GC_add_roots(static_cast<char *>(sctx.sp) - sctx.size, sctx.sp);
return sctx;
}
void deallocate(boost::context::stack_context sctx) override {
GC_remove_roots(static_cast<char *>(sctx.sp) - sctx.size, sctx.sp);
stack.deallocate(sctx);
}
};
static BoehmGCStackAllocator boehmGCStackAllocator;
#endif
@ -257,6 +286,8 @@ void initGC()
GC_set_oom_fn(oomHandler);
StackAllocator::defaultAllocator = &boehmGCStackAllocator;
/* 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
we don't need to garbage collect at all. (Collection has a