[Bug driver/79974] New: First line of file is printed with unrecognized -mtune x86 option

[noloader at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79974

            Bug ID: 79974
           Summary: First line of file is printed with unrecognized -mtune
                    x86 option
           Product: gcc
           Version: 5.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: driver
          Assignee: unassigned at gcc dot gnu.org
          Reporter: noloader at gmail dot com
  Target Milestone: ---

I'm working on a VIA C7-D processor. GCC version is 5.4.0 from Ubuntu. I'm
attempting to use GCC's -mtune=c7 option
(https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html):

  $ cat test.cxx
  // Test file

  int main(int argc, char* argv[])
  {
      return 0;
  }

Attempting to compile results in:

  $ g++ -march=native -mtune=c7 test.cxx -o test.exe
  test.cxx:1:0: error: bad value (c7) for -mtune= switch
   // Test file
   ^

Flagging line 0 of the file seems unusual, especially since its just a comment.
It seems like the -mtune error should be printed and nothing more because the
comment has nothing to do with the issue.

I recall seeing the unusual output on Cygwin when using -fPIC. The Cygwin
behavior was fixed, IIRC.

**********

$ gcc --version
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.2 LTS
Release:        16.04
Codename:       xenial