[PATCH] Decorate COW string methods with std::_RequireInputIte
François Dumont
frs.dumont@gmail.com
Tue Jul 28 17:00:54 GMT 2026
Sorry for previous patch, I was too focus on _GLIBCXX_DEBUG mode and
tend to forget that template methods can be exported.
Let's try with this less enthusiast version then.
I've split the patch, so the subject change. The small _GLIBCXX_DEBUG
parts left will come in a future patch, not implying new symbols thought.
For now I think just adding _RequireInputIte and remove in C++11 useless
methods is fine.
libstdc++: Decorate COW string methods with std::_RequireInputIte
Add the std::_RequireInputIter constraints on members taking template
iterator range to avoid the "do the right thing" ambiguity.
Thanks to this requirement remove, in post-C++11, associated
dispatch methods.
libstdc++v3/ChangeLog:
* include/bits/cow_string.h
(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.
(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::_M_replace_dispatch
(iterator, iterator, _Integer, _Integer, __true_type)): Remove.
[__cplusplus < 201103L](basic_string::_S_construct_aux):
Remove.
[__cplusplus < 201103L](basic_string::_S_construct_aux_2):
Remove.
(basic_string::_S_construct): Adapt.
Tested under Linux x86_64 testsuite/21_strings/* C++98 & C++23 including
abi check.
Ok to commit ?
François
On 7/21/26 13:19, Jonathan Wakely wrote:
> On Tue, 21 Jul 2026 at 07:43, Jonathan Wakely<jwakely@redhat.com> wrote:
>> On Tue, 21 Jul 2026 at 05:57, François Dumont<frs.dumont@gmail.com> wrote:
>>> 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 thestd::_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&):
>>> Addstd::_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 thestd::_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.
>> You've added a new member function, basic_string::_M_replace. Why
>> doesn't that need to be exported from the shared library?
>>
>> Why don't the changes to the signature of basic_string::assign and
>> basic_string::append change the exported symbols?
> As expected, 'make check-abi' fails:
>
> Running /home/jwakely/src/gcc/gcc/libstdc++-v3/testsuite/libstdc++-abi/abi.exp
> ...
> FAIL: libstdc++-abi/abi_check
>
> === libstdc++ Summary ===
>
> # of unexpected failures 1
>
>
>>> Ok to commit ?
> Definitely not.
>
-------------- next part --------------
diff --git a/libstdc++-v3/include/bits/cow_string.h b/libstdc++-v3/include/bits/cow_string.h
index 0f1a2e082d0..a3f9195c098 100644
--- a/libstdc++-v3/include/bits/cow_string.h
+++ b/libstdc++-v3/include/bits/cow_string.h
@@ -721,7 +721,12 @@ _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)
@@ -1391,7 +1396,12 @@ _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); }
@@ -1551,7 +1561,12 @@ _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); }
@@ -1657,7 +1672,12 @@ _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); }
@@ -2143,14 +2163,23 @@ _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());
+#if __cplusplus >= 201103L
+ typedef std::__false_type _Integral;
+#else
typedef typename std::__is_integer<_InputIterator>::__type _Integral;
+#endif
return _M_replace_dispatch(__i1, __i2, __k1, __k2, _Integral());
}
@@ -2295,11 +2324,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif // C++17
private:
+#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 +2345,7 @@ _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>
@@ -2337,13 +2369,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static _CharT*
_S_construct_aux_2(size_type __req, _CharT __c, const _Alloc& __a)
{ return _S_construct(__req, __c, __a); }
+#endif
template<class _InIterator>
static _CharT*
_S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a)
{
+#if __cplusplus < 201103L
typedef typename std::__is_integer<_InIterator>::__type _Integral;
return _S_construct_aux(__beg, __end, __a, _Integral());
+#else
+ return _S_construct(__beg, __end, __a,
+ std::__iterator_category(__beg));
+#endif
}
// For Input Iterators, used in istreambuf_iterators, etc.
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