[Bug c/67957] New: gcc's printf attribute accepts %m as a format character

[Bug c/67957] New: gcc's printf attribute accepts %m as a format character

[christos at zoulas dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67957

            Bug ID: 67957
           Summary: gcc's printf attribute accepts %m as a format
                    character
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: christos at zoulas dot com
  Target Milestone: ---

According to TOG
(http://pubs.opengroup.org/onlinepubs/009695399/functions/fprintf.html), %m is
not a legal formatting character for printf(3) like functions. Some
implementations (glibc) accept this formatting character as an extension and
expand it to the error string via strerror(3) that errno currently points to.
Most other c library implementations do not expand %m. 

Attached is a patch that makes printf warn when %m is present and adds a
"syslog" attribute that accepts %m. I recognize that this is an incompatible
change, and I welcome suggestions how to do this in a less intrusive way.

I tried to mininize the size of the patch; there are better ways to do this,
but require more refactoring.

[Bug c/67957] gcc's printf attribute accepts %m as a format character

[christos at zoulas dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67957

--- Comment #1 from Christos Zoulas <christos at zoulas dot com> ---
Created attachment 36504
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36504&action=edit
patch

[Bug c/67957] gcc's printf attribute accepts %m as a format character

[schwab@linux-m68k.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67957

Andreas Schwab <schwab@linux-m68k.org> changed:

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

--- Comment #2 from Andreas Schwab <schwab@linux-m68k.org> ---
.

*** This bug has been marked as a duplicate of bug 67956 ***