https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70732
--- Comment #2 from Krzysztof Małysa <krzyk240 at gmail dot com> --- I read some code from unwind-dw2-fde.c and it makes sense. In the code above, stack unwinding happens in low memory conditions which causes unsuccessful memory allocations and because of deep recursion, there are so many of them. But maybe it is reasonable to make an optimization to not flood system with many, many unsuccessful syscalls (brk() and mmap2()). It's important to note that stack unwinding happens at the bottom of recursion (so it's unlikely that there will be more memory available - see https://github.com/gcc-mirror/gcc/blob/master/libgcc/unwind-dw2-fde.c#L957), also look at these syscalls which malloc makes: brk(0xcad8000) = 0xcab4000 mmap2(NULL, 1048576, ...) = -1 It tries to expand stack (which is not successful due to deep recursion that was made) and to map 1MB of memory, what is very much compared to what is needed, so it will almost always result in malloc() returning NULL. That is why it doesn't make much sense to call malloc() all the time if there is no memory available while we're freeing only small chunks of memory. All in all, I agree that there is no bug, but I think that it's a good opportunity to make an optimization here.
