[llvm-bugs] [Bug 52219] New: invocation of next_permutation will not compile when using libc++

via llvm-bugs llvm-bugs at lists.llvm.org
Tue Oct 19 07:36:06 PDT 2021


            Bug ID: 52219
           Summary: invocation of next_permutation will not compile when
                    using libc++
           Product: libc++
           Version: 11.0
          Hardware: PC
                OS: other
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: edward.vogel at hpe.com
                CC: llvm-bugs at lists.llvm.org, mclow.lists at gmail.com

The following program compiles with clang and the g++ headers, but will not
compile using the libc++ headers.  Visual Studio also cleanly compiles the

Perhaps the program is invalid, but other headers do allow it.

Here is a cut/paste from a cygwin session:

$ cat t.cpp

#include <algorithm>
using namespace std;
struct S {
  S(char ch = 0) : c(ch) {}
  S(const S& x) {
  S& operator=(const S& x) {
   return (*this);
  S& operator=(char ch) {
   return (*this);
  bool operator<(const S& x) {
   return (c == x.c);
  char c;

int main(int, char *[])
        S a[10];
        next_permutation(a, a + 1);

VogelEd at XLB3502Q4E ~
$ clang++ t.cpp

VogelEd at XLB3502Q4E ~
$ clang++   -stdlib=libc++ t.cpp
In file included from t.cpp:3:
/usr/include/c++/v1/algorithm:716:71: error: invalid operands to binary
      expression ('const S' and 'const S')
    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
                                                                  ~~~ ^ ~~~
/usr/include/c++/v1/algorithm:5612:13: note: in instantiation of member
      'std::__1::__less<S, S>::operator()' requested here
        if (__comp(*--__i, *__ip1))
<remaining messages removed>

Not important, just thought I'd post it.

Thanks again for your time,

Ed Vogel

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