[Bug c++/110226] New: GCC ignores include of non-existent header

[jpegqs at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110226

            Bug ID: 110226
           Summary: GCC ignores include of non-existent header
           Product: gcc
           Version: 13.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jpegqs at gmail dot com
  Target Milestone: ---

Try compiling this code with g++:

#if __has_include("quadmath123.h")
#endif
#include <quadmath123.h>

You shouldn't have "quadmath123.h", but GCC will compile this without error.
Reproduced in every version of GCC since __has_include was supported (GCC
4.9.2).

Occurs in Boost headers when <quadmath.h> is not installed.