[Bug preprocessor/98021] New: #warning issues redundant diagnostic lines

["eggert at cs dot ucla.edu" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98021

            Bug ID: 98021
           Summary: #warning issues redundant diagnostic lines
           Product: gcc
           Version: 10.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: eggert at cs dot ucla.edu
  Target Milestone: ---

I ran into this problem when building something from Gnulib. For the following
program foo.c:

#warning "GCC might issue a bogus -Wreturn-local-addr warning here."
#warning "See <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93644>."

The command 'gcc -S foo.c' issues the following diagnostics, which are too
repetitive:

foo.c:1:2: warning: #warning "GCC might issue a bogus -Wreturn-local-addr
warning here." [-Wcpp]
    1 | #warning "GCC might issue a bogus -Wreturn-local-addr warning here."
      |  ^~~~~~~
foo.c:2:2: warning: #warning "See
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93644>." [-Wcpp]
    2 | #warning "See <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93644>."
      |  ^~~~~~~

GCC should simply output something like this instead:

foo.c:1:2: warning: GCC might issue a bogus -Wreturn-local-addr warning here.
[-Wcpp]
foo.c:2:2: warning: See <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93644>.
[-Wcpp]