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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r9-10058] libstdc++: Do not allocate a zero-size vector<bool> [PR 100153] Date: Mon, 9 May 2022 16:40:10 +0000 (GMT) [thread overview] Message-ID: <20220509164010.7DA323857373@sourceware.org> (raw) https://gcc.gnu.org/g:b4a170bf3a2b0397a5d73f7cac24f6df4298569e commit r9-10058-gb4a170bf3a2b0397a5d73f7cac24f6df4298569e Author: Jonathan Wakely <jwakely@redhat.com> Date: Tue Apr 20 16:16:13 2021 +0100 libstdc++: Do not allocate a zero-size vector<bool> [PR 100153] The vector<bool>::shrink_to_fit() implementation will allocate new storage even if the vector is empty. That then leads to the end-of-storage pointer being non-null and equal to the _M_start._M_p pointer, which means that _M_end_addr() has undefined behaviour. The fix is to stop doing a useless zero-sized allocation in shrink_to_fit(), so that _M_start._M_p and _M_end_of_storage are both null after an empty vector shrinks. Signed-off-by: Jonathan Wakely <jwakely@redhat.com> libstdc++-v3/ChangeLog: PR libstdc++/100153 * include/bits/vector.tcc (vector<bool>::_M_shrink_to_fit()): When size() is zero just deallocate and reset. (cherry picked from commit 681707ec28d56494fa61a80c62500724d55f8586) Diff: --- libstdc++-v3/include/bits/vector.tcc | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/bits/vector.tcc b/libstdc++-v3/include/bits/vector.tcc index 497d9f72247..7d56c63134a 100644 --- a/libstdc++-v3/include/bits/vector.tcc +++ b/libstdc++-v3/include/bits/vector.tcc @@ -944,7 +944,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER return false; __try { - _M_reallocate(size()); + if (size_type __n = size()) + _M_reallocate(__n); + else + { + this->_M_deallocate(); + this->_M_impl._M_reset(); + } return true; } __catch(...)
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