In this case your approach is indeed the simplest fix to do.
libstdc++: [_GLIBCXX_DEBUG] Fix COW string valid range check
In revision 698a6af5dcbae5d935bcda8a461dea8458c658dc the
_GLIBCXX_DEBUG code
for the Library Defect 438 has been removed for C++11 and after.
But the COW basic_string implementation used when
_GLIBCXX_USE_CXX11_ABI=0 is
missing the _RequireInputIter constraint on a number method
resulting in test
failures.
For the moment move the culprit __glibcxx_requires_valid_range call
in a method
where the iterator type has already been checked.
libstdc++-v3/ChangeLog:
* include/bits/cow_string.h
(basic_string::replace(iterator, iterator, _InputIte,
_InputIte)): Move
__glibcxx_requires_valid_range to...
(basic_string::_M_replace_dispatch(iterator, iterator,
_InputIte,
_InputIte, __fase_type)): ...here.
* testsuite/21_strings/basic_string/debug/append_neg.cc:
New test case.
* testsuite/21_strings/basic_string/debug/assign_neg.cc:
New test case.
* testsuite/21_strings/basic_string/debug/construct_neg.cc:
New test case.
* testsuite/21_strings/basic_string/debug/insert_neg.cc:
New test case.
* testsuite/21_strings/basic_string/debug/replace_neg.cc:
New test case.
Tested under Linux x86_64 _GLIBCXX_DEBUG mode C++98 and C++11.
Ok to commit ?
François
On 3/30/26 19:13, Jonathan Wakely wrote:
On Thu, 26 Mar 2026 at 21:46, François Dumont <[email protected]> wrote:
Hi
Here is the fix to the current COW basic_string issue now that I've
removed the DR438 _GLIBCXX_DEBUG code.
I've also revisited the location of the debug checks so that for example
on the append_neg.cc test case we have this assertion message with the
cxx11 string:
In function:
constexpr std::cxx11::basic_string<_CharT, _Traits, _Alloc>& std::
cxx11::basic_string<_CharT, _Traits, _Alloc>::replace(const_iterator,
const_iterator, _InputIterator, _InputIterator) [with _InputIterator =
so refering to the replace method. Whereas on the cow string:
In function:
std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT,
_Traits, _Alloc>::append(_InputIterator, _InputIterator) [with
_InputIterator = gnu_debug::_Safe_iterator<gnu_cxx::
I plan to do something similar on cxx11 string. Let me know if useless.
libstdc++: [_GLIBCXX_DEBUG] Fix COW basic_string checks
In revision 698a6af5dcbae5d935bcda8a461dea8458c658dc the
_GLIBCXX_DEBUG code
for the Library Defect 438 has been removed for C++11 and after.
But the COW
basic_string implementation used when _GLIBCXX_USE_CXX11_ABI=0 was
missing
the _RequireInputIter constraint on a number method resulting in
test failures.
_RequireInputIter is now added where necessary. And _GLIBCXX_DEBUG
checks have
been added at the right place to benefit from more accurate
assertion messages.
libstdc++-v3/ChangeLog:
* include/bits/cow_string.h [__cplusplus >= 201103L]
(basic_string(_InputIte, _InputIte, const _Alloc&)): Add
_RequireInputIter
template parameter. Add
__glibcxx_requires_valid_constructor_range call.
(_M_replace_dispatch(_InputIte, _InputIte): New.
(_M_replace_dispatch(iterator, iterator, _InputIte,
_InputIte): New.
[__cplusplus >= 201103L]
(append(_InputIte, _InputIte)): Add _RequireInputIter
template parameter.
Add __glibcxx_requires_valid_constructor_range call. Use
latter.
(insert(iterator, _InputIte, _InputIte)): Likewise.
(replace(iterator, iterator, _InputIte, _InputIte)): Likewise.
(_S_construct(_InputIte, _InputIte, const _Alloc&)): Add
_RequireInputIter
template parameter.
* include/debug/debug.h
(__glibcxx_requires_valid_construtor_range): New.
* testsuite/21_strings/basic_string/debug/append_neg.cc:
New test case.
* testsuite/21_strings/basic_string/debug/assign_neg.cc:
New test case.
* testsuite/21_strings/basic_string/debug/construct_neg.cc:
New test case.
* testsuite/21_strings/basic_string/debug/insert_neg.cc:
New test case.
* testsuite/21_strings/basic_string/debug/replace_neg.cc:
New test case.
Tested under Linux x64_86.
Ok to commit ?
This seems like a large change to stable std::string code, which is
inappropriate when we're just a few weeks from releasing GCC 16.
I would prefer to just move the assertion macro to
_M_replace_dispatch, or only check the assertions for !_Integral, as
in the patches I showed.
For GCC 17 we can revisit this and apply your fixes.
diff --git a/libstdc++-v3/include/bits/cow_string.h
b/libstdc++-v3/include/bits/cow_string.h
index 6cf00224372..df71185e556 100644
--- a/libstdc++-v3/include/bits/cow_string.h
+++ b/libstdc++-v3/include/bits/cow_string.h
@@ -2124,7 +2124,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
_GLIBCXX_DEBUG_PEDASSERT(_M_ibegin() <= __i1 && __i1 <= __i2
&& __i2 <= _M_iend());
- __glibcxx_requires_valid_range(__k1, __k2);
typedef typename std::__is_integer<_InputIterator>::__type _Integral;
return _M_replace_dispatch(__i1, __i2, __k1, __k2, _Integral());
}
@@ -3833,6 +3832,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_replace_dispatch(iterator __i1, iterator __i2, _InputIterator __k1,
_InputIterator __k2, __false_type)
{
+ __glibcxx_requires_valid_range(__k1, __k2);
const basic_string __s(__k1, __k2);
const size_type __n1 = __i2 - __i1;
_M_check_length(__n1, __s.size(), "basic_string::_M_replace_dispatch");
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/debug/append_neg.cc
b/libstdc++-v3/testsuite/21_strings/basic_string/debug/append_neg.cc
new file mode 100644
index 00000000000..befe83a84f3
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/debug/append_neg.cc
@@ -0,0 +1,19 @@
+// { dg-do run { xfail *-*-* } }
+// { dg-require-debug-mode "" }
+
+#include <vector>
+#include <string>
+
+void test01()
+{
+ std::vector<char> v1(10, 'a');
+ std::string s2;
+
+ s2.append(v1.begin() + 7, v1.begin() + 2);
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/debug/assign_neg.cc
b/libstdc++-v3/testsuite/21_strings/basic_string/debug/assign_neg.cc
new file mode 100644
index 00000000000..5f32c170f50
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/debug/assign_neg.cc
@@ -0,0 +1,19 @@
+// { dg-do run { xfail *-*-* } }
+// { dg-require-debug-mode "" }
+
+#include <vector>
+#include <string>
+
+void test01()
+{
+ std::vector<char> v1(10, 'a');
+ std::string s2;
+
+ s2.assign(v1.begin() + 7, v1.begin() + 2);
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
diff --git
a/libstdc++-v3/testsuite/21_strings/basic_string/debug/construct_neg.cc
b/libstdc++-v3/testsuite/21_strings/basic_string/debug/construct_neg.cc
new file mode 100644
index 00000000000..1ac933d4309
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/debug/construct_neg.cc
@@ -0,0 +1,17 @@
+// { dg-do run { xfail *-*-* } }
+// { dg-require-debug-mode "" }
+
+#include <vector>
+#include <string>
+
+void test01()
+{
+ std::vector<char> v1(10, 'a');
+ std::string s2(v1.begin() + 7, v1.begin() + 2);
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/debug/insert_neg.cc
b/libstdc++-v3/testsuite/21_strings/basic_string/debug/insert_neg.cc
new file mode 100644
index 00000000000..95530ef2a51
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/debug/insert_neg.cc
@@ -0,0 +1,19 @@
+// { dg-do run { xfail *-*-* } }
+// { dg-require-debug-mode "" }
+
+#include <vector>
+#include <string>
+
+void test01()
+{
+ std::vector<char> v1(10, 'a');
+ std::string s2;
+
+ s2.insert(s2.begin(), v1.begin() + 7, v1.begin() + 2);
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
diff --git
a/libstdc++-v3/testsuite/21_strings/basic_string/debug/replace_neg.cc
b/libstdc++-v3/testsuite/21_strings/basic_string/debug/replace_neg.cc
new file mode 100644
index 00000000000..fd3df9e8539
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/debug/replace_neg.cc
@@ -0,0 +1,20 @@
+// { dg-do run { xfail *-*-* } }
+// { dg-require-debug-mode "" }
+
+#include <vector>
+#include <string>
+
+void test01()
+{
+ std::vector<char> v1(10, 'a');
+ std::string s2 = "bbbbbbbbbb";
+
+ s2.replace(s2.begin(), s2.begin() + 5,
+ v1.begin() + 7, v1.begin() + 2);
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
