[Bug c/62228] New: gcc : expected identifier before numeric constant

[ankzzdev at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62228

            Bug ID: 62228
           Summary: gcc : expected identifier before numeric constant
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ankzzdev at gmail dot com

Created attachment 33379
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33379&action=edit
Header and C file used to reproduce this issue

I have attached the header file and c-code (t.c and t.h) used to reproduce this
issue.

# make t
cc     t.c   -o t
t.c: In function 'main':
t.c:8: error: expected identifier before numeric constant
make: *** [t] Error 1

Error is due to this piece of code in multi-line macro.
#define LOG(module, level, msg) \
    if ( (module)->level ) \
    msg_log(msg)


While verifying the pre-processed output of the c-code:
# gcc -E t.c
...
int main()
{
    struct logger module;
    if ( (&module)->0 ) msg_log("Ooops\n");
    return 0;
}
# cat t.c
#include <stdio.h>

#include "t.h"

int main()
{
    struct logger module;
    LOG(&module, 0, "Ooops\n");
    return 0;
}    


Here we can see the Macro LOG is wrongly getting interpreted. 
LOG(&module, 0, "Ooops\n"); ==> if ( (&module)->0 ) msg_log("Ooops\n");

This is happening as "level" in macro is getting replaced with a value "0".
Leading to the issue:  expected identifier before numeric constant