[Bug c/38575] New: free() accept argument that has the same name with standard/builtin function

[Bug c/38575] New: free() accept argument that has the same name with standard/builtin function

[m dot shulhan at gmail dot com]

Any variable that has the same name with standard/builtin function name will be
accepted by free parameter.

example of code,

>>>
#include <stdlib.h>
int main(int argc, char *argv[])
{
        free(rand);
        return 0;
}
<<<

This sample code will success on compile,

$ gcc -Wall -g -O0 free-bug.c

but error on run,

$ ./a.out

*** glibc detected *** ./a.out: free(): invalid pointer: 0x08048364 ***
======= Backtrace: =========
/lib/libc.so.6[0xb7ee94b6]
/lib/libc.so.6(cfree+0x89)[0xb7eeb179]
./a.out[0x8048421]
/lib/libc.so.6(__libc_start_main+0xe0)[0xb7e98fe0]
./a.out[0x80483a1]
======= Memory map: ========
08048000-08049000 r-xp 00000000 08:03 7946378   
/home/rv77ax/doc/sandbox/c/a.out
08049000-0804a000 r--p 00000000 08:03 7946378   
/home/rv77ax/doc/sandbox/c/a.out
0804a000-0804b000 rw-p 00001000 08:03 7946378   
/home/rv77ax/doc/sandbox/c/a.out
0804b000-0806c000 rw-p 0804b000 00:00 0          [heap]
b7e76000-b7e80000 r-xp 00000000 08:01 817696     /lib/libgcc_s.so.1
b7e80000-b7e82000 rw-p 00009000 08:01 817696     /lib/libgcc_s.so.1
b7e82000-b7e83000 rw-p b7e82000 00:00 0
b7e83000-b7fb0000 r-xp 00000000 08:01 817612     /lib/libc-2.6.1.so
b7fb0000-b7fb1000 r--p 0012c000 08:01 817612     /lib/libc-2.6.1.so
b7fb1000-b7fb3000 rw-p 0012d000 08:01 817612     /lib/libc-2.6.1.so
b7fb3000-b7fb6000 rw-p b7fb3000 00:00 0
b7fcb000-b7fcc000 rw-p b7fcb000 00:00 0
b7fcc000-b7fe6000 r-xp 00000000 08:01 819693     /lib/ld-2.6.1.so
b7fe6000-b7fe8000 rw-p 0001a000 08:01 819693     /lib/ld-2.6.1.so
bfd0a000-bfd20000 rw-p bfd0a000 00:00 0          [stack]
ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
Aborted


-- 
           Summary: free() accept argument that has the same name with
                    standard/builtin function
           Product: gcc
           Version: 4.2.1
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: m dot shulhan at gmail dot com
 GCC build triplet: -Wall -g -O0
  GCC host triplet: i586-suse-linux
GCC target triplet: i586-suse-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38575

[Bug c/38575] free() accept argument that has the same name with standard/builtin function

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2008-12-19 03:16 -------
Yes you are passing free a function pointer.  a function decays to a function
pointer and an implicit conversion to void* happens.
If you use -pedantic you get an error message as a function pointer cannot be
converted to void* in standard C:
t.c:4: error: ISO C forbids passing argument 1 of 'free' between function
pointer and 'void *'
/usr/include/stdlib.h:159: note: expected 'void *' but argument is of type 'int
(*)(void)'


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38575

[Bug middle-end/38575] free() accept argument that has the same name with standard/builtin function

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2008-12-19 03:18 -------
Now maybe maybe_emit_free_warning should be enhanced to warn about this.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|minor                       |enhancement
          Component|c                           |middle-end


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38575

[Bug middle-end/38575] free() accept argument that has the same name with standard/builtin function

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38575

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.6.0

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-02-01 22:25:49 UTC ---
t7.c:4:13: warning: attempt to free a non-heap object [-Wfree-nonheap-object]
Fixed in 4.6.0 and above.