https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87784
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Looks like this patch fixes it:
--- a/libstdc++-v3/include/tr2/dynamic_bitset
+++ b/libstdc++-v3/include/tr2/dynamic_bitset
@@ -729,8 +729,7 @@ namespace tr2
{
if (size_t __offset = this->size() % bits_per_block == 0)
this->_M_do_append_block(block_type(0), this->_M_Nb);
- ++this->_M_Nb;
- this->_M_unchecked_set(this->_M_Nb, __bit);
+ this->_M_unchecked_set(this->_M_Nb++, __bit);
}
/**
