This probably has never actually affected anyone in practice. The normal ABI implementation just uses malloc and only falls back to the pool on malloc failure. But if that happens a bunch of times the freelist gets out of order which violates some of the invariants of the freelist (as well as the comments that follow the bug). The bug is just a comparison reversal when traversing the freelist in the case where the pointer being returned to the pool is after the existing freelist.
I'm not sure what to do as far as the test suite is concerned. It's a private part of the implementation of the exception handling ABI and it can only ever be triggered if malloc fails (repeatedly). So it seems like reproducing it from the external interface will require hooking malloc to forcibly return NULL. But I'm a newb on these lists, so will obediently do as instructed.
diff --git a/libstdc++-v3/ChangeLog-2022 b/libstdc++-v3/ChangeLog-2022 new file mode 100644 index 00000000000..8057de58539 --- /dev/null +++ b/libstdc++-v3/ChangeLog-2022 @@ -0,0 +1,4 @@ +2022-08-16 Keef Aragon <keef.ara...@konscious.net> + + * libstdc++-v3/libsupc++/eh_alloc.cc: inverse comparison in pool::free + diff --git a/libstdc++-v3/libsupc++/eh_alloc.cc b/libstdc++-v3/libsupc++/eh_alloc.cc index c85b9aed40b..cad2750e3b9 100644 --- a/libstdc++-v3/libsupc++/eh_alloc.cc +++ b/libstdc++-v3/libsupc++/eh_alloc.cc @@ -225,7 +225,7 @@ namespace for (fe = &first_free_entry; (*fe)->next && (reinterpret_cast <char *> ((*fe)->next) - > reinterpret_cast <char *> (e) + sz); + < reinterpret_cast <char *> (e) + sz); fe = &(*fe)->next) ; // If we can merge the next block into us do so and continue
