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libstdc++: Do not allocate a zero-size vector<bool> [PR 100153]

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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.
This commit is contained in:
Jonathan Wakely 2021-04-20 16:16:13 +01:00
parent 741c7350c0
commit 681707ec28
1 changed files with 7 additions and 1 deletions
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8
libstdc++-v3/include/bits/vector.tcc
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@ -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(...)