[Bug c++/55602] New: Does not generate Error message for redefined macros

[Bug c++/55602] New: Does not generate Error message for redefined macros

[guojiufu at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55602

             Bug #: 55602
           Summary: Does not generate Error message for redefined macros
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: guojiufu@gmail.com


gcc and g++ generate warning message(do not generate any information if there
is '#pragma GCC system_header' is the header) instead an error message for
redefined macros. While in standard it seems require an error. 

Second paragraph of section "Macro replacement" in C standard:
--------
An identifier currently defined as an object-like macro shall not be redefined
by another #define preprocessing directive unless the second definition is an
object-like macro definition and the two replacement lists are identical.
Likewise, an identifier currently defined as a function-like macro shall not be
redefined by another #define preprocessing directive unless the second
definition is a function-like macro definition that has the same number and
spelling of parameters, and the two replacement lists are identical.
----------
C++ standard: Second paragraph of section "Macro replacement"
---------
An identifier currently defined as an object-like macro may be redefined by
another #define preprocessing directive provided that the second definition is
an object-like macro definition and the two replacement lists are identical,
otherwise the program is ill-formed. Likewise, an identifier currently defined
as a function-like macro may be redefined by another #define preprocessing
directive provided that the second definition is a function-like macro
definition that has the same number and spelling of parameters, and the two
replacement lists are identical, otherwise the program is ill-formed.
------------------


case:
a.h
----------------
#define A 1
#define A 2
---------------

a.c
---------------
#include "a.h"

int main(){
  return A;
}
--------------

[Bug preprocessor/55602] Does not generate Error message for redefined macros

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55602

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-12-05 05:00:05 UTC ---
Use -pedantic-errors.

[Bug preprocessor/55602] Does not generate Error message for redefined macros

[guojiufu at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55602

--- Comment #2 from Jeff Guo <guojiufu at gmail dot com> 2012-12-10 11:57:57 UTC ---
-pedantic-errors is helpful if the redefined macros not guarded by "#pragma GCC
system_header"
--a.h --
#pragma GCC system_header
#define A 1
#define A 2
-----a.c----
#include "a.h"

int main(){
  return A;
}

----------------

[Bug preprocessor/55602] Does not generate Error message for redefined macros

[guojiufu at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55602

--- Comment #3 from Jeff Guo <guojiufu at gmail dot com> 2012-12-10 11:59:07 UTC ---
Above case is still no error message reported even with -pedantic-errors

[Bug preprocessor/55602] Does not generate Error message for redefined macros

[guojiufu at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55602

Jeff Guo <guojiufu at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |VERIFIED
         Resolution|INVALID                     |WONTFIX

--- Comment #4 from Jeff Guo <guojiufu at gmail dot com> 2012-12-10 12:02:29 UTC ---
may GCC report error message for redefined macro if -pedantic-errors specified
for system headers?

[Bug preprocessor/55602] Does not generate Error message for redefined macros

[guojiufu at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55602

Jeff Guo <guojiufu at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|VERIFIED                    |CLOSED

--- Comment #5 from Jeff Guo <guojiufu at gmail dot com> 2012-12-26 02:26:34 UTC ---
using -pedantic-errors is helpful