[Bug c/19113] New: Assigning to va_list var is valid for va_arg calls but not other cases

[Bug c/19113] New: Assigning to va_list var is valid for va_arg calls but not other cases

[hjl at lucon dot org]

With gcc 3.4.3, I got

[hjl@gnu-20 tmp]$ cat a.c
#include <stdarg.h>
void
foo(int l, ...)
{
   va_list p,q,r;
   va_start(p,l);
#if WORK
   q = va_arg(p,va_list);
#else
/* The following code fails */
   q = r;
#endif
}
[hjl@gnu-20 tmp]$ gcc -S a.c
a.c: In function `foo':
a.c:11: incompatible types in assignment
[hjl@gnu-20 tmp]$ gcc -S a.c -DWORK

It used to work in gcc 2.96:

[hjl@gnu-6 tmp]$ gcc -S a.c
[hjl@gnu-6 tmp]$ gcc -v
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.2 2.96-128.7.2)

Is that a bug or a feature?

-- 
           Summary: Assigning to va_list var is valid for va_arg calls but
                    not other cases
           Product: gcc
           Version: 3.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hjl at lucon dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19113

[Bug c/19113] Assigning to va_list var is valid for va_arg calls but not other cases

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-12-21 18:43 -------
Use va_copy as this is invalid c.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19113

[Bug c/19113] Assigning to va_list var is valid for va_arg calls but not other cases

[joseph at codesourcery dot com]

------- Additional Comments From joseph at codesourcery dot com  2004-12-21 19:27 -------
Subject: Re:  Assigning to va_list var is valid for va_arg calls
 but not other cases

On Tue, 21 Dec 2004, pinskia at gcc dot gnu dot org wrote:

> Use va_copy as this is invalid c.

The compile-time validity depends on whether va_list is an array type (in 
which case it should be rejected at compile-time) or some other object 
type (in which case it shouldn't).  Copying other than with va_copy is 
merely undefined behavior at runtime.

However, I can't reproduce the original bug report on x86 which would 
appear to be the target to which it was referring (from the compiler used 
for comparison).  x86-64 does use an array type so the reported behavior 
would be correct on that target.



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19113