https://gcc.gnu.org/g:9d5baaa92c6609191fd2488389562ac1ad1f0fb2
commit r14-11510-g9d5baaa92c6609191fd2488389562ac1ad1f0fb2
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Fri Mar 28 15:41:41 2025 +0000
libstdc++: Fix -Warray-bounds warning in std::vector<bool> [PR110498]
In this case, we need to tell the compiler that the current size is not
larger than the new size so that all the existing elements can be copied
to the new storage. This avoids bogus warnings about overflowing the new
storage when the compiler can't tell that that cannot happen.
We might as well also hoist the loads of begin() and end() before the
allocation too. All callers will have loaded at least begin() before
calling _M_reallocate.
libstdc++-v3/ChangeLog:
PR libstdc++/110498
* include/bits/vector.tcc (vector<bool, A>::_M_reallocate):
Hoist loads of begin() and end() before allocation and use them
to state an unreachable condition.
* testsuite/23_containers/vector/bool/capacity/110498.cc: New
test.
Reviewed-by: Tomasz Kamiński <tkami...@redhat.com>
(cherry picked from commit aa3aaf2bfb8fcc17076993df4297597b68bc5f60)
Diff:
---
libstdc++-v3/include/bits/vector.tcc | 5 ++++-
.../23_containers/vector/bool/capacity/110498.cc | 18 ++++++++++++++++++
2 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/libstdc++-v3/include/bits/vector.tcc
b/libstdc++-v3/include/bits/vector.tcc
index dafc2a31a8b4..c59c15beacd9 100644
--- a/libstdc++-v3/include/bits/vector.tcc
+++ b/libstdc++-v3/include/bits/vector.tcc
@@ -1059,9 +1059,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
vector<bool, _Alloc>::
_M_reallocate(size_type __n)
{
+ const iterator __begin = begin(), __end = end();
+ if (size_type(__end - __begin) > __n)
+ __builtin_unreachable();
_Bit_pointer __q = this->_M_allocate(__n);
iterator __start(std::__addressof(*__q), 0);
- iterator __finish(_M_copy_aligned(begin(), end(), __start));
+ iterator __finish(_M_copy_aligned(__begin, __end, __start));
this->_M_deallocate();
this->_M_impl._M_start = __start;
this->_M_impl._M_finish = __finish;
diff --git
a/libstdc++-v3/testsuite/23_containers/vector/bool/capacity/110498.cc
b/libstdc++-v3/testsuite/23_containers/vector/bool/capacity/110498.cc
new file mode 100644
index 000000000000..d2d09e10d19a
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/vector/bool/capacity/110498.cc
@@ -0,0 +1,18 @@
+// { dg-options "-O3 -Werror=array-bounds" }
+// { dg-do compile }
+
+// Bug libstdc++/110498
+// Spurious warnings stringop-overflow and array-bounds copying data as bytes
+// into vector::reserve
+
+#include <vector>
+
+void f(std::vector<bool>& v)
+{
+ // Warning emitted when set to any number in the range [1,64].
+ const std::size_t reserve_size = 30;
+
+ v.reserve(reserve_size);
+ v.push_back(0);
+}
+
