[Bug c/44586] New: gcc does not warn about casting non-variadic types to variadic types

[Bug c/44586] New: gcc does not warn about casting non-variadic types to variadic types

[raj dot khem at gmail dot com]

the folowing testcase does a casting which results in undefined behaviour but
gcc does not warn about it.

ypedef int (*bar_t)(int x, int y, ...);

int foo(int x, int y) {
        return x+y;
}

void f(int x, int y) {
       bar_t bar;

       /* Cast foo to variadic type... undefined behaviour */
       bar = (bar_t) foo;
       (*bar)(x,y);
}


-- 
           Summary: gcc does not warn about casting non-variadic types to
                    variadic types
           Product: gcc
           Version: 4.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: raj dot khem at gmail dot com
 GCC build triplet: x86_64-linux-gnu
  GCC host triplet: x86_64-linux-gnu
GCC target triplet: x86_64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44586

[Bug c/44586] gcc does not warn about casting non-variadic types to variadic types

[manu at gcc dot gnu dot org]

------- Comment #1 from manu at gcc dot gnu dot org  2010-06-20 21:41 -------
Joseph, what do you think? Any suggestions where this may be catched? wording?
option?

I have wished for some time to create a -Wundefined option anyway.


-- 

manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu dot org,
                   |                            |jsm28 at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44586

[Bug c/44586] gcc does not warn about casting non-variadic types to variadic types

[joseph at codesourcery dot com]

------- Comment #2 from joseph at codesourcery dot com  2010-06-20 22:17 -------
Subject: Re:  gcc does not warn about casting non-variadic types
 to variadic types

It's not the conversion that's undefined, but the call.  You could have an 
option to warn for all function pointer conversions to incompatible 
function pointer types (but they have reasonable uses as there isn't a 
generic function pointer type like void *) - or you could have the 
optimizers detect calls to incompatibly cast types and warn then like the 
front ends does when the cast appears directly in the call.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44586

[Bug c/44586] gcc does not warn about casting non-variadic types to variadic types

[manu at gcc dot gnu dot org]

------- Comment #3 from manu at gcc dot gnu dot org  2010-06-20 22:25 -------
OK. So I would say confirmed, but still I am not sure how I would implement
this. So patches welcome.


-- 

manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2010-06-20 22:25:41
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44586