[Bug c++/115067] New: Bogus -O2 -Wnull-dereference for istreambuf_iterator

[Bug c++/115067] New: Bogus -O2 -Wnull-dereference for istreambuf_iterator

[hewillk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115067

            Bug ID: 115067
           Summary: Bogus -O2 -Wnull-dereference for istreambuf_iterator
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hewillk at gmail dot com
  Target Milestone: ---

#include <sstream>
#include <iterator>
#include <iostream>

std::string fn() {
  std::istringstream is {"bob"};
  auto beg = std::istreambuf_iterator<char>(is);
  auto end = std::istreambuf_iterator<char>();
  return {beg, end};
}

int main() {
  std::cout << fn() << "\n";
}

https://godbolt.org/z/rGqW5he87

The above code always triggers the following warning when -O2
-Wnull-dereference is used since GCC-12:

/opt/compiler-explorer/gcc-trunk-20240513/include/c++/15.0.0/streambuf:495:30:
error: potential null pointer dereference [-Werror=null-dereference]
  495 |       egptr() const { return _M_in_end; }
      |                              ^~~~~~~~~
In member function 'std::basic_streambuf<_CharT, _Traits>::char_type*
std::basic_streambuf<_CharT, _Traits>::gptr() const [with _CharT = char;
_Traits = std::char_traits<char>]',
    inlined from 'std::basic_streambuf<_CharT, _Traits>::int_type
std::basic_streambuf<_CharT, _Traits>::sbumpc() [with _CharT = char; _Traits =
std::char_traits<char>]' at
/opt/compiler-explorer/gcc-trunk-20240513/include/c++/15.0.0/streambuf:326:33,
    inlined from 'std::istreambuf_iterator<_CharT, _Traits>&
std::istreambuf_iterator<_CharT, _Traits>::operator++() [with _CharT = char;
_Traits = std::char_traits<char>]' at
/opt/compiler-explorer/gcc-trunk-20240513/include/c++/15.0.0/bits/streambuf_iterator.h:173:17,
    inlined from 'void std::__cxx11::basic_string<_CharT, _Traits,
_Alloc>::_M_construct(_InIterator, _InIterator, std::input_iterator_tag) [with
_InIterator = std::istreambuf_iterator<char, std::char_traits<char> >; _CharT =
char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at
/opt/compiler-explorer/gcc-trunk-20240513/include/c++/15.0.0/bits/basic_string.tcc:182:6,
    inlined from 'std::__cxx11::basic_string<_CharT, _Traits,
_Alloc>::basic_string(_InputIterator, _InputIterator, const _Alloc&) [with
_InputIterator = std::istreambuf_iterator<char, std::char_traits<char> >;
<template-parameter-2-2> = void; _CharT = char; _Traits =
std::char_traits<char>; _Alloc = std::allocator<char>]' at
/opt/compiler-explorer/gcc-trunk-20240513/include/c++/15.0.0/bits/basic_string.h:770:16,
    inlined from 'std::string fn()' at <source>:9:19:
/opt/compiler-explorer/gcc-trunk-20240513/include/c++/15.0.0/streambuf:492:30:
error: potential null pointer dereference [-Werror=null-dereference]
  492 |       gptr()  const { return _M_in_cur;  }

[Bug middle-end/115067] Bogus -O2 -Wnull-dereference for istreambuf_iterator

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115067

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Dup

*** This bug has been marked as a duplicate of bug 105580 ***