Previously the _M_Nb member was incremented before calling
_M_unchecked_set which meant that the bit being set was out of bounds.
It either set the wrong bit in an allocated word, or accessed beyond the
end of the allocated memory in the _M_w vector. The fix for the bug is
to update the _M_Nb member after using it as an index.
As an optimisation, when a new block needs to be appended the call to
_M_unchecked_set can be avoided by appending a block with the least
significant bit already set to the desired value.
PR libstdc++/87784
* include/tr2/dynamic_bitset (dynamic_bitset::push_back): When there
are no unused bits in the last block, append a new block with the
right value so the bit doesn't need to be set. Only increment size
after setting the new bit, not before.
* testsuite/tr2/dynamic_bitset/pr87784.cc: New test.
From-SVN: r265625
Jakub Jelinek
Jonathan Wakely
Richard Sandiford
Edward Smith-Rowland