[Bug c/107448] New: GCC no longer diagnoses missing input file with -MG

[boris at kolpackov dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107448

            Bug ID: 107448
           Summary: GCC no longer diagnoses missing input file with -MG
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: boris at kolpackov dot net
  Target Milestone: ---

With GCC 10 when trying to extract dependency information with -MG we get
diagnostics if the input file does not exist:

$ g++-10 -M -MG /tmp/no-such-file.cxx
g++-10: error: /tmp/no-such-file.cxx: No such file or directory
g++-10: fatal error: no input files
compilation terminated.

$ echo $?
1

In GCC 11 and 12 this diagnostics is gone:

$ g++-11 -M -MG /tmp/no-such-file.cxx
$ echo $?
1

$ g++-12 -M -MG /tmp/no-such-file.cxx
$ echo $?
1