[llvm-bugs] [Bug 30357] New: Unexpected compile time error with vector<bool>

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=30357

            Bug ID: 30357
           Summary: Unexpected compile time error with vector<bool>
           Product: libc++
           Version: 3.8
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: billy.jasiniecki at hpe.com
                CC: llvm-bugs at lists.llvm.org, mclow.lists at gmail.com
    Classification: Unclassified

An test case (that is an excerpt from a standard validation test) gets an error
when compiled with both g++ and clang, but only with headers from libc++.  When
the same test case is compiled using gnu headers, the test compiles cleanly.

The test case:

#include <vector>
struct alloc : std::allocator<bool> {};
int main(void)
{
        std::vector<bool> v1;
        std::vector<bool, alloc>::reference r01 = v1[0];
}


With clang:

$ clang -c t.cpp -std=c++11 -Ic:/downloads/libcxx-3.8.1.src/include
t265.cpp:6:45: error: no viable conversion from '__bit_reference<vector<[...],
      std::__1::allocator<bool>>>' to
      '__bit_reference<vector<[...], alloc>>'
        std::vector<bool, alloc>::reference r01 = v1[0];
                                            ^     ~~~~~
c:/downloads/libcxx-3.8.1.src/include/__bit_reference:35:7: note: candidate
      constructor (the implicit copy constructor) not viable: no known
      conversion from 'reference' (aka '__bit_reference<std::__1::vector<bool,
      std::__1::allocator<bool> > >') to 'const
      std::__1::__bit_reference<std::__1::vector<bool, alloc>, true> &' for 1st
      argument
class __bit_reference
      ^
c:/downloads/libcxx-3.8.1.src/include/__bit_reference:51:31: note: candidate
      function
    _LIBCPP_INLINE_VISIBILITY operator bool() const _NOEXCEPT
                              ^
1 error generated.

With g++:

$ g++ -c t.cpp -std=c++11 -Ic:/downloads/libcxx-3.8.1.src/include
t265.cpp: In function ‘int main()’:
t265.cpp:6:55: error: conversion from ‘std::__1::vector<bool>::reference {aka
std::__1::__bit_reference<std::__1::vector<bool>, true>}’ to non-scalar type
‘std::__1::vector<bool, alloc>::reference {aka
std::__1::__bit_reference<std::__1::vector<bool, alloc>, true>}’ requested
         std::vector<bool, alloc>::reference r01 = v1[0];


The test case also compiles cleanly when headers from Dinkumware are used.

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