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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - std::max_element causes an invalid static assert error in algorithm:2505:5: error: static_assert failed due to requirement '__is_forward_iterator<Iterator>::value' "std::max_element requires a ForwardIterator""
href="https://bugs.llvm.org/show_bug.cgi?id=40698">40698</a>
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</tr>
<tr>
<th>Summary</th>
<td>std::max_element causes an invalid static assert error in algorithm:2505:5: error: static_assert failed due to requirement '__is_forward_iterator<Iterator>::value' "std::max_element requires a ForwardIterator"
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
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<th>Hardware</th>
<td>Macintosh
</td>
</tr>
<tr>
<th>OS</th>
<td>MacOS X
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>vincent.lebourlot@starqube.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr></table>
<p>
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<pre>The following code generates a compilation error although the iterator being
marked as a forward iterator. This code compiles correctly on gcc 7.3.0.
~~~
#include <algorithm>
class Iterator:std::iterator<std::forward_iterator_tag,size_t>{
public:
bool operator==(Iterator ter)const noexcept{return true;}
bool operator!=(Iterator ter)const noexcept{return false;}
Iterator operator++()const noexcept{return *this;}
size_t operator*()const noexcept{return 42;}
};
int main(){
Iterator begin,end;
std::max_element(begin,end,[](size_t,size_t){return true;});
return 0;
}
~~~
full error report:
/usr/local/bin/clang++ -g -isysroot
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
-std=gnu++17 -o CMakeFiles/bug.dir/src/bug.cpp.o -c
CLionProjects/untitled/src/bug.cpp
In file included from CLionProjects/untitled/src/bug.cpp:1:
/usr/local/bin/../include/c++/v1/algorithm:2505:5: error: static_assert failed
due to requirement '__is_forward_iterator<Iterator>::value' "std::max_element
requires a ForwardIterator"
static_assert(__is_forward_iterator<_ForwardIterator>::value,
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CLionProjects/untitled/src/bug.cpp:13:7: note: in instantiation of function
template specialization 'std::__1::max_element<Iterator, (lambda at
CLionProjects/untitled/src/bug.cpp:13:29)>' requested here
std::max_element(begin,end,[](size_t,size_t){return true;});</pre>
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