[Bug c/50154] New: attribute printf and scanf should imply attribute nonnull

[Bug c/50154] New: attribute printf and scanf should imply attribute nonnull

[bruno at clisp dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50154

             Bug #: 50154
           Summary: attribute printf and scanf should imply attribute
                    nonnull
    Classification: Unclassified
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: bruno@clisp.org


Created attachment 25076
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=25076
test case

When a function is declared as taking a printf or scanf format string, gcc
gives a warning when a format string with invalid syntax is passed. It should
also give a warning when a NULL format string is passed.

How to reproduce:
Save the test case file as foo.c.
$ gcc -Wformat=2 -c foo.c
[no warning]
$ gcc -Wformat=2 -c foo.c -DDECLARE_NONNULL
foo.c: In function 'foo':
foo.c:10:3: warning: null argument where non-null required (argument 3)
[-Wnonnull]

Rationale:
1) ISO C 99 specifies that the printf and scanf format strings must be
"multibyte
character sequences"; that excludes NULL.
See ISO C 99 sections 7.19.6.1 paragraph 3 and 7.19.6.2 paragraph 3.
2) Passing NULL as first argument to printf crashes the program on FreeBSD,
Solaris, and other platforms.

[Bug c/50154] attribute printf and scanf should imply attribute nonnull

[bruno at clisp dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50154

bruno at clisp dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #25076|0                           |1
        is obsolete|                            |

--- Comment #1 from bruno at clisp dot org 2011-08-22 16:29:26 UTC ---
Created attachment 25077
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=25077
test case (corrected)

[Bug c/50154] attribute printf and scanf should imply attribute nonnull

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50154

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
           Severity|normal                      |enhancement

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-08-24 21:15:37 UTC ---
I think it is better if the person adds nonnull attribute themselves rather
than GCC adding it with the printf format.

[Bug c/50154] attribute printf and scanf should imply attribute nonnull

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50154

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |jakub at gcc dot gnu.org
         Resolution|                            |INVALID

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-08-25 11:13:59 UTC ---
Yeah, I agree with that.