[Bug preprocessor/81419] New: GCC wrongly suggests function-like macro as fixit hint for undefined object-like macro

[egall at gwmail dot gwu.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81419

            Bug ID: 81419
           Summary: GCC wrongly suggests function-like macro as fixit hint
                    for undefined object-like macro
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: egall at gwmail dot gwu.edu
                CC: dmalcolm at redhat dot com
  Target Milestone: ---
              Host: i386-apple-darwin9.8.0
            Target: i386-apple-darwin9.8.0
             Build: i386-apple-darwin9.8.0

Testcase: 

$ cat macro_fixit.c
#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))

int foo(unsigned int argument);

int bar(void)
{
        return foo(PTR_SIZE);
}

Compiling gives:

$ /usr/local/bin/gcc -c macro_fixit.c
macro_fixit.c: In function ‘bar’:
macro_fixit.c:7:13: error: ‘PTR_SIZE’ undeclared (first use in this function);
did you mean ‘ARRAY_SIZE’?
  return foo(PTR_SIZE);
             ^~~~~~~~
             ARRAY_SIZE
macro_fixit.c:7:13: note: each undeclared identifier is reported only once for
each function it appears in

However, making the replacement that the fixit hint suggests is invalid, and
still leads to another error:

$ /usr/local/bin/gcc -c macro_fixit.c
macro_fixit.c: In function ‘bar’:
macro_fixit.c:7:13: error: ‘ARRAY_SIZE’ undeclared (first use in this function)
  return foo(ARRAY_SIZE);
             ^~~~~~~~~~
macro_fixit.c:7:13: note: each undeclared identifier is reported only once for
each function it appears in

IMO gcc should only suggest replacements as fixit hints when they actually fix
the problem being pointed out.

Version info:

$ /usr/local/bin/gcc -v
Using built-in specs.
COLLECT_GCC=/usr/local/bin/gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/i386-apple-darwin9.8.0/8.0.0/lto-wrapper
Target: i386-apple-darwin9.8.0
Configured with: ../configure --disable-werror --disable-werror-always
--enable-languages=c,c++,lto,objc,obj-c++ --enable-stage1-checking=release,rtl
-C --with-system-libunwind --enable-secureplt --enable-frame-pointer
--enable-debug --with-isl --disable-host-shared --enable-maintainer-mode
--disable-default-pie --with-ld64 --without-pic --enable-target-optspace
CC=/usr/local/bin/gcc CXX=/usr/local/bin/g++ AUTOCONF=/usr/local/bin/autoconf
AUTOHEADER=/usr/local/bin/autoheader AUTORECONF=/usr/local/bin/autoreconf
AUTOM4TE=/usr/local/bin/autom4te AUTOSCAN=/usr/local/bin/autoscan
AUTOUPDATE=/usr/local/bin/autoupdate IFNAMES=/usr/local/bin/ifnames
Thread model: posix
gcc version 8.0.0 20170702 (experimental) (GCC)