[gcc r16-7433] libstdc++: Fix incorrect noexcept on string::compare overloads [PR123991]
Jonathan Wakely
redi@gcc.gnu.org
Tue Feb 10 10:42:33 GMT 2026
https://gcc.gnu.org/g:0912dfcd1e901d7dc1ff5e10528eefe3f3ff7b22
commit r16-7433-g0912dfcd1e901d7dc1ff5e10528eefe3f3ff7b22
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Mon Feb 9 10:48:44 2026 +0000
libstdc++: Fix incorrect noexcept on string::compare overloads [PR123991]
These compare overloads throw when the pos index is out of range, not
only when the const T& parameter throws on conversion to string_view.
Remove the incorrect conditional noexcept-specifier from the two
overloads that can throw.
libstdc++-v3/ChangeLog:
PR libstdc++/123991
* include/bits/basic_string.h (compare(size_type, size_type, T)):
Remove noexcept-specifier.
(compare(size_type, size_type, T, size_type, size_type)):
Likewise.
* include/bits/cow_string.h (compare(size_type, size_type, T)):
Remove noexcept-specifier.
(compare(size_type, size_type, T, size_type, size_type)):
Likewise.
* testsuite/21_strings/basic_string/operations/compare/char/123991.cc:
New test.
* testsuite/21_strings/basic_string/operations/compare/wchar_t/123991.cc:
New test.
Reviewed-by: Nathan Myers <nmyers@redhat.com>
Diff:
---
libstdc++-v3/include/bits/basic_string.h | 2 -
libstdc++-v3/include/bits/cow_string.h | 2 -
.../basic_string/operations/compare/char/123991.cc | 56 ++++++++++++++++++++++
.../operations/compare/wchar_t/123991.cc | 56 ++++++++++++++++++++++
4 files changed, 112 insertions(+), 4 deletions(-)
diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index 0602b0dcac88..cd6f312f1bd2 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -3524,7 +3524,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
_GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
_If_sv<_Tp, int>
compare(size_type __pos, size_type __n, const _Tp& __svt) const
- noexcept(is_same<_Tp, __sv_type>::value)
{
__sv_type __sv = __svt;
return __sv_type(*this).substr(__pos, __n).compare(__sv);
@@ -3545,7 +3544,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
_If_sv<_Tp, int>
compare(size_type __pos1, size_type __n1, const _Tp& __svt,
size_type __pos2, size_type __n2 = npos) const
- noexcept(is_same<_Tp, __sv_type>::value)
{
__sv_type __sv = __svt;
return __sv_type(*this)
diff --git a/libstdc++-v3/include/bits/cow_string.h b/libstdc++-v3/include/bits/cow_string.h
index 36c19fabfc5b..6cf002243729 100644
--- a/libstdc++-v3/include/bits/cow_string.h
+++ b/libstdc++-v3/include/bits/cow_string.h
@@ -2998,7 +2998,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp>
_If_sv<_Tp, int>
compare(size_type __pos, size_type __n, const _Tp& __svt) const
- noexcept(is_same<_Tp, __sv_type>::value)
{
__sv_type __sv = __svt;
return __sv_type(*this).substr(__pos, __n).compare(__sv);
@@ -3018,7 +3017,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_If_sv<_Tp, int>
compare(size_type __pos1, size_type __n1, const _Tp& __svt,
size_type __pos2, size_type __n2 = npos) const
- noexcept(is_same<_Tp, __sv_type>::value)
{
__sv_type __sv = __svt;
return __sv_type(*this)
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/compare/char/123991.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/compare/char/123991.cc
new file mode 100644
index 000000000000..53ef2d4606c6
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/compare/char/123991.cc
@@ -0,0 +1,56 @@
+// { dg-do run { target c++17 } }
+
+// Bug 123991 - std::string::compare crashes instead of throwing
+
+#include <string>
+#include <string_view>
+#include <stdexcept>
+#include <testsuite_hooks.h>
+
+void
+test_compare_3arg()
+{
+ std::string_view sv;
+ std::string s;
+ static_assert( ! noexcept(s.compare(0, 0, sv)) );
+#ifdef __cpp_exceptions
+ try
+ {
+ (void) s.compare(1, 0, sv);
+ VERIFY(false);
+ }
+ catch (const std::out_of_range&)
+ { }
+#endif
+}
+
+void
+test_compare_5arg()
+{
+ std::string_view sv;
+ std::string s;
+ static_assert( ! noexcept(s.compare(0, 0, sv, 0, 0)) );
+#ifdef __cpp_exceptions
+ try
+ {
+ (void) s.compare(1, 0, sv, 0, 0);
+ VERIFY(false);
+ }
+ catch (const std::out_of_range&)
+ { }
+
+ try
+ {
+ (void) s.compare(0, 0, sv, 1, 0);
+ VERIFY(false);
+ }
+ catch (const std::out_of_range&)
+ { }
+#endif
+}
+
+int main()
+{
+ test_compare_3arg();
+ test_compare_5arg();
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/compare/wchar_t/123991.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/compare/wchar_t/123991.cc
new file mode 100644
index 000000000000..c4188bbff8b2
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/compare/wchar_t/123991.cc
@@ -0,0 +1,56 @@
+// { dg-do run { target c++17 } }
+
+// Bug 123991 - std::string::compare crashes instead of throwing
+
+#include <string>
+#include <string_view>
+#include <stdexcept>
+#include <testsuite_hooks.h>
+
+void
+test_compare_3arg()
+{
+ std::wstring_view sv;
+ std::wstring s;
+ static_assert( ! noexcept(s.compare(0, 0, sv)) );
+#ifdef __cpp_exceptions
+ try
+ {
+ (void) s.compare(1, 0, sv);
+ VERIFY(false);
+ }
+ catch (const std::out_of_range&)
+ { }
+#endif
+}
+
+void
+test_compare_5arg()
+{
+ std::wstring_view sv;
+ std::wstring s;
+ static_assert( ! noexcept(s.compare(0, 0, sv, 0, 0)) );
+#ifdef __cpp_exceptions
+ try
+ {
+ (void) s.compare(1, 0, sv, 0, 0);
+ VERIFY(false);
+ }
+ catch (const std::out_of_range&)
+ { }
+
+ try
+ {
+ (void) s.compare(0, 0, sv, 1, 0);
+ VERIFY(false);
+ }
+ catch (const std::out_of_range&)
+ { }
+#endif
+}
+
+int main()
+{
+ test_compare_3arg();
+ test_compare_5arg();
+}
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