Some custom iterators are incompatible with standard algorithms #946
Description
Containers that return raw pointers (like Array or SortedSet) work well with standard algorithms, but the ones that use custom iterators (like juce_CharPointer_UFT8 for strings or HashMap::Iterator) do not.
When compiling the following code with GCC-11...
#include <JuceHeader.h>
#include <algorithm>
static bool complex_test(juce::juce_wchar const c)
{
/* do some complex test... */
return c == 'o';
};
int main (int argc, char* argv[])
{
juce::String const string{ "foo" };
auto const valid{ std::all_of(string.begin(), string.end(), complex_test) };
return valid ? 0 : 1;
}...we get the following error :
In file included from /usr/include/c++/11/algorithm:62,
from ../../JuceLibraryCode/modules/juce_core/system/juce_StandardHeader.h:46,
from ../../JuceLibraryCode/modules/juce_core/juce_core.h:203,
from ../../JuceLibraryCode/JuceHeader.h:16,
from ../../Source/Main.cpp:1:
/usr/include/c++/11/bits/stl_algo.h: In instantiation of ‘_InputIterator std::__find_if_not(_InputIterator, _InputIterator, _Predicate) [with _InputIterator = juce::CharPointer_UTF8; _Predicate = __gnu_cxx::__ops::_Iter_pred<bool (*)(wchar_t)>]’:
/usr/include/c++/11/bits/stl_algo.h:513:32: required from ‘_IIter std::find_if_not(_IIter, _IIter, _Predicate) [with _IIter = juce::CharPointer_UTF8; _Predicate = bool (*)(wchar_t)]’
/usr/include/c++/11/bits/stl_algo.h:453:40: required from ‘bool std::all_of(_IIter, _IIter, _Predicate) [with _IIter = juce::CharPointer_UTF8; _Predicate = bool (*)(wchar_t)]’
../../Source/Main.cpp:14:34: required from here
/usr/include/c++/11/bits/stl_algo.h:108:53: error: no matching function for call to ‘__iterator_category(juce::CharPointer_UTF8&)’
108 | std::__iterator_category(__first));
| ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~
In file included from /usr/include/c++/11/bits/stl_algobase.h:65,
from /usr/include/c++/11/algorithm:61,
from ../../JuceLibraryCode/modules/juce_core/system/juce_StandardHeader.h:46,
from ../../JuceLibraryCode/modules/juce_core/juce_core.h:203,
from ../../JuceLibraryCode/JuceHeader.h:16,
from ../../Source/Main.cpp:1:
/usr/include/c++/11/bits/stl_iterator_base_types.h:238:5: note: candidate: ‘template<class _Iter> constexpr typename std::iterator_traits< <template-parameter-1-1> >::iterator_category std::__iterator_category(const _Iter&)’
238 | __iterator_category(const _Iter&)
| ^~~~~~~~~~~~~~~~~~~
/usr/include/c++/11/bits/stl_iterator_base_types.h:238:5: note: template argument deduction/substitution failed:
/usr/include/c++/11/bits/stl_iterator_base_types.h: In substitution of ‘template<class _Iter> constexpr typename std::iterator_traits< <template-parameter-1-1> >::iterator_category std::__iterator_category(const _Iter&) [with _Iter = juce::CharPointer_UTF8]’:
/usr/include/c++/11/bits/stl_algo.h:108:32: required from ‘_InputIterator std::__find_if_not(_InputIterator, _InputIterator, _Predicate) [with _InputIterator = juce::CharPointer_UTF8; _Predicate = __gnu_cxx::__ops::_Iter_pred<bool (*)(wchar_t)>]’
/usr/include/c++/11/bits/stl_algo.h:513:32: required from ‘_IIter std::find_if_not(_IIter, _IIter, _Predicate) [with _IIter = juce::CharPointer_UTF8; _Predicate = bool (*)(wchar_t)]’
/usr/include/c++/11/bits/stl_algo.h:453:40: required from ‘bool std::all_of(_IIter, _IIter, _Predicate) [with _IIter = juce::CharPointer_UTF8; _Predicate = bool (*)(wchar_t)]’
../../Source/Main.cpp:14:34: required from here
/usr/include/c++/11/bits/stl_iterator_base_types.h:238:5: error: no type named ‘iterator_category’ in ‘struct std::iterator_traits<juce::CharPointer_UTF8>’
Compilation also fails with Clang-10. MSVC compiles without problem.
If we define the standard iterator traits in juce_CharPointerUTF8, it seems to solve the issue.
class CharPointer_UTF8 final
{
public:
using value_type = juce::juce_wchar;
using pointer = value_type*;
using reference = value_type&;
using iterator_category = std::bidirectional_iterator_tag;
// not sure if this last one makes sense, since
// `int operator-(CharPointer_UTF8 lhs, CharPointer_UTF8 rhs);`
// is not defined. Maybe it should?
using difference_type = int;
// ...
};