[PATCH][_GLIBCXX_DEBUG] Enhance COW basic_string checks
François Dumont
frs.dumont@gmail.com
Tue Jul 21 04:57:43 GMT 2026
Here is the new commit message:
libstdc++: [_GLIBCXX_DEBUG] Improve COW basic_string checks
Put the __glibcxx_requires_valid_range checks at public member level
so that diagnostics are giving directly the culprit member name.
Add the std::_RequireInputIter constraints on members taking template
iterator range to avoid the "do the right thing" ambiguity.
libstdc++v3/ChangeLog:
* include/bits/cow_string.h
(basic_string::_M_replace): New.
(basic_string(_InputIterator, _InputIterator, const _Alloc&):
Add std::_RequireInputIter constraint and
__glibcxx_requires_valid_constructor_range check.
(basic_string::append(_InputIte, _InputIte): Add
std::_RequireInputIter
constraint and __glibcxx_requires_valid_range check. Call
_M_replace.
(basic_string::assign(_InputIte, _InputIte): Likewise.
(basic_string::insert(iterator, _InputIte, _InputIte)):
Likewise.
(basic_string::replace(iterator, iterator, _InputIte,
_InputIte)): Likewise.
[__cplusplus >= 201103L](basic_string::_S_construct): New.
(basic_string::_M_replace_dispatch(iterator, iterator,
_InputIte, _InputIte,
__false_type)): Remove __glibcxx_requires_valid_range check.
* include/debug/debug.h
(__glibcxx_requires_valid_constructor_range): New.
On 7/6/26 22:42, Jonathan Wakely wrote:
> On Mon, 15 Jun 2026 at 07:07 +0200, François Dumont wrote:
>> Hi
>>
>> libstdc++: [_GLIBCXX_DEBUG] Improve COW basic_string checks
>>
>> Put the __glibcxx_requires_valid_range checks at public member level
>> so that diagnostics are giving directly the invoked member name.
>>
>> Add the std::_RequireInputIter constraints on members taking
>> template
>> iterator range to avoid the "do the right thing" ambiguity
>> without the help of __is_integer.
>>
>> libstdc++v3/ChangeLog:
>>
>> * include/bits/cow_string.h
>> (basic_string::_M_replace): New.
>> (basic_string(_InputIterator, _InputIterator, const
>> _Alloc&): Add
>> std::_RequireInputIter constraint and
>> __glibcxx_requires_valid_constructor_range
>
> Please fix the line-wrapping here. Try to keep the lines to < 72
> characters so that when indented by 'git log' they fit below 80.
>
>> check.
>> (basic_string::append(_InputIte, _InputIte): Add
>> std::_RequireInputIter
>> constraint and __glibcxx_requires_valid_range check. Call
>> _M_replace.
>> (basic_string::assign(_InputIte, _InputIte): Likewise.
>> (basic_string::insert(iterator, _InputIte, _InputIte)):
>> Likewise.
>> (basic_string::replace(iterator, iterator, _InputIte,
>> _InputIte)): Likewise.
>> [__cplusplus >= 201103L](basic_string::_S_construct): New.
>> (basic_string::_M_replace_dispatch(iterator, iterator,
>> _InputIte, _InputIte,
>> __false_type)): Remove __glibcxx_requires_valid_range check.
>> * include/debug/debug.h
>> (__glibcxx_requires_valid_constructor_range): New.
>>
>> Tested under Linux x86_64 with _GLIBCXX_USE_CXX11_ABI=0 and
>> _GLIBCXX_DEBUG.
>
> Did you test C++98 as well as the default -std modes?
I hadn't but now did, ex:
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::
normal_iterator<char*, std::vector<char, std::allocator<char> > >,
std::
debug::vector<char>, std::random_access_iterator_tag>; _CharT = char;
_Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
Error: function requires a valid iterator range [first, last).
Objects involved in the operation:
iterator "first" @ 0x7ffc9027e5a0 {
type = gnu_cxx::normal_iterator<char*, std::vector<char,
std::allocator<char> > > (mutable iterator);
state = dereferenceable;
references sequence with type 'std::debug::vector<char,
std::allocator<char> >' @ 0x7ffc9027e750
}
iterator "last" @ 0x7ffc9027e600 {
type = gnu_cxx::normal_iterator<char*, std::vector<char,
std::allocator<char> > > (mutable iterator);
state = dereferenceable;
references sequence with type 'std::debug::vector<char,
std::allocator<char> >' @ 0x7ffc9027e750
}
XFAIL: 21_strings/basic_string/debug/append_neg.cc -std=gnu++98
execution test
>
> Doesn't this require new symbols to be exported by the linker script?
>
I don't think so. Maybe you had in mind the
__gnu_debug::__check_valid_range but that's a template function
implemented inline.
Ok to commit ?
-------------- next part --------------
diff --git a/libstdc++-v3/include/bits/cow_string.h b/libstdc++-v3/include/bits/cow_string.h
index 0f1a2e082d0..1e088f22241 100644
--- a/libstdc++-v3/include/bits/cow_string.h
+++ b/libstdc++-v3/include/bits/cow_string.h
@@ -721,10 +721,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @param __end End of range.
* @param __a Allocator to use (default is default allocator).
*/
- template<class _InputIterator>
+#if __cplusplus >= 201103L
+ template<typename _InputIterator,
+ typename = std::_RequireInputIter<_InputIterator>>
+#else
+ template<typename _InputIterator>
+#endif
basic_string(_InputIterator __beg, _InputIterator __end,
const _Alloc& __a = _Alloc())
- : _M_dataplus(_S_construct(__beg, __end, __a), __a)
+ : _M_dataplus(_S_construct(
+ __glibcxx_requires_valid_constructor_range(__beg, __end),
+ __end, __a), __a)
{ }
#ifdef __glibcxx_string_view // >= C++17
@@ -1391,10 +1398,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*
* Appends characters in the range [__first,__last) to this string.
*/
- template<class _InputIterator>
+#if __cplusplus >= 201103L
+ template<typename _InputIterator,
+ typename = std::_RequireInputIter<_InputIterator>>
+#else
+ template<typename _InputIterator>
+#endif
basic_string&
append(_InputIterator __first, _InputIterator __last)
- { return this->replace(_M_iend(), _M_iend(), __first, __last); }
+ {
+ __glibcxx_requires_valid_range(__first, __last);
+ return _M_replace(_M_iend(), _M_iend(), __first, __last);
+ }
#ifdef __glibcxx_string_view // >= C++17
/**
@@ -1551,10 +1566,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*
* Sets value of string to characters in the range [__first,__last).
*/
- template<class _InputIterator>
+#if __cplusplus >= 201103L
+ template<typename _InputIterator,
+ typename = std::_RequireInputIter<_InputIterator>>
+#else
+ template<typename _InputIterator>
+#endif
basic_string&
assign(_InputIterator __first, _InputIterator __last)
- { return this->replace(_M_ibegin(), _M_iend(), __first, __last); }
+ {
+ __glibcxx_requires_valid_range(__first, __last);
+ return _M_replace(_M_ibegin(), _M_iend(), __first, __last);
+ }
#if __glibcxx_containers_ranges // C++ >= 23
/**
@@ -1657,10 +1680,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* length_error is thrown. The value of the string doesn't
* change if an error is thrown.
*/
- template<class _InputIterator>
+#if __cplusplus >= 201103L
+ template<typename _InputIterator,
+ typename = std::_RequireInputIter<_InputIterator>>
+#else
+ template<typename _InputIterator>
+#endif
void
insert(iterator __p, _InputIterator __beg, _InputIterator __end)
- { this->replace(__p, __p, __beg, __end); }
+ {
+ _GLIBCXX_DEBUG_PEDASSERT(_M_ibegin() <= __p && __p <= _M_iend());
+ __glibcxx_requires_valid_range(__beg, __end);
+ _M_replace(__p, __p, __beg, __end);
+ }
#if __glibcxx_containers_ranges // C++ >= 23
/**
@@ -2143,15 +2175,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* The value of the string doesn't change if an error is
* thrown.
*/
- template<class _InputIterator>
+#if __cplusplus >= 201103L
+ template<typename _InputIterator,
+ typename = std::_RequireInputIter<_InputIterator>>
+#else
+ template<typename _InputIterator>
+#endif
basic_string&
replace(iterator __i1, iterator __i2,
_InputIterator __k1, _InputIterator __k2)
{
_GLIBCXX_DEBUG_PEDASSERT(_M_ibegin() <= __i1 && __i1 <= __i2
&& __i2 <= _M_iend());
- typedef typename std::__is_integer<_InputIterator>::__type _Integral;
- return _M_replace_dispatch(__i1, __i2, __k1, __k2, _Integral());
+ __glibcxx_requires_valid_range(__k1, __k2);
+ return _M_replace(__i1, __i2, __k1, __k2);
}
// Specializations for the common case of pointer and iterator:
@@ -2295,11 +2332,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif // C++17
private:
+ template<class _InputIterator>
+ basic_string&
+ _M_replace(iterator __i1, iterator __i2,
+ _InputIterator __k1, _InputIterator __k2)
+ {
+#if __cplusplus < 201103L
+ typedef typename std::__is_integer<_InputIterator>::__type _Integral;
+#else
+ using _Integral = std::__false_type;
+#endif
+ return _M_replace_dispatch(__i1, __i2, __k1, __k2, _Integral());
+ }
+
+#if __cplusplus < 201103L
template<class _Integer>
basic_string&
_M_replace_dispatch(iterator __i1, iterator __i2, _Integer __n,
_Integer __val, __true_type)
{ return _M_replace_aux(__i1 - _M_ibegin(), __i2 - __i1, __n, __val); }
+#endif
template<class _InputIterator>
basic_string&
@@ -2314,6 +2366,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_replace_safe(size_type __pos1, size_type __n1, const _CharT* __s,
size_type __n2);
+#if __cplusplus < 201103L
// _S_construct_aux is used to implement the 21.3.1 para 15 which
// requires special behaviour if _InIter is an integral type
template<class _InIterator>
@@ -2345,6 +2398,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
typedef typename std::__is_integer<_InIterator>::__type _Integral;
return _S_construct_aux(__beg, __end, __a, _Integral());
}
+#else
+ template<typename _InIterator>
+ static _CharT*
+ _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a)
+ {
+ return _S_construct(__beg, __end, __a,
+ std::__iterator_category(__beg));
+ }
+#endif
// For Input Iterators, used in istreambuf_iterators, etc.
template<class _InIterator>
@@ -3858,7 +3920,6 @@ _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/include/debug/debug.h b/libstdc++-v3/include/debug/debug.h
index 5604f98e4d3..aabb9af2271 100644
--- a/libstdc++-v3/include/debug/debug.h
+++ b/libstdc++-v3/include/debug/debug.h
@@ -65,6 +65,8 @@ namespace __gnu_debug
# define __glibcxx_requires_cond(_Cond,_Msg)
# define __glibcxx_requires_valid_range(_First,_Last)
+# define __glibcxx_requires_valid_constructor_range(_First,_Last) \
+ _First
# define __glibcxx_requires_can_increment(_First,_Size)
# define __glibcxx_requires_can_increment_range(_First1,_Last1,_First2)
# define __glibcxx_requires_can_decrement_range(_First1,_Last1,_First2)
@@ -92,6 +94,8 @@ namespace __gnu_debug
# define __glibcxx_requires_cond(_Cond,_Msg) _GLIBCXX_DEBUG_VERIFY(_Cond,_Msg)
# define __glibcxx_requires_valid_range(_First,_Last) \
__glibcxx_check_valid_range(_First,_Last)
+# define __glibcxx_requires_valid_constructor_range(_First,_Last) \
+ __glibcxx_check_valid_constructor_range(_First,_Last)
# define __glibcxx_requires_can_increment(_First,_Size) \
__glibcxx_check_can_increment(_First,_Size)
# define __glibcxx_requires_can_increment_range(_First1,_Last1,_First2) \
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