libstdc++: Check for size overflow in constexpr allocation [PR105957]

libstdc++-v3/ChangeLog:

	PR libstdc++/105957
	* include/bits/allocator.h (allocator::allocate): Check for
	overflow in constexpr allocation.
	* testsuite/20_util/allocator/105975.cc: New test.

1 files changed, 18 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/20_util/allocator/105975.cc b/libstdc++-v3/testsuite/20_util/allocator/105975.cc
new file mode 100644
index 00000000000..4342aeade04
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/allocator/105975.cc
@@ -0,0 +1,18 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do compile { target c++20 } }
+
+// PR libstdc++/105957
+
+#include <memory>
+
+consteval bool test_pr105957()
+{
+  std::allocator<long long> a;
+  auto n = std::size_t(-1) / (sizeof(long long) - 1);
+  auto p = a.allocate(n); // { dg-error "constexpr" }
+  a.deallocate(p, n);
+  return true;
+}
+static_assert( test_pr105957() );
+
+// { dg-error "throw_bad_array_new_length" "" { target *-*-* } 0 }