[Bug c/55791] New: gcc fails to detect wrong type in sizeof in malloc

[Bug c/55791] New: gcc fails to detect wrong type in sizeof in malloc

[dcb314 at hotmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55791

             Bug #: 55791
           Summary: gcc fails to detect wrong type in sizeof in malloc
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dcb314@hotmail.com


Given the following code, culled from customer code,

# include <stdlib.h>

extern void g(char *);

void f()
{
    char *p;

    // wrong type in sizeof in malloc
    p = (char *) malloc( 10 * sizeof( char *));

    g(p);
}

gcc can't detect that the malloc line should be something closer to

    p = (char *) malloc( 10 * sizeof( char));

i.e. the type in the sizeof expression must be the same as (or 
at very least the same size as) the type of destination buffer.

[Bug c/55791] gcc fails to detect wrong type in sizeof in malloc

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55791

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

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

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-12-22 17:57:02 UTC ---
I think for GCC it is hard to detect this as sizeof is changed into a constant
integer early on.

[Bug c/55791] gcc fails to detect wrong type in sizeof in malloc

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55791

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
We have -Wsizeof-pointer-memaccess warning for memcpy/memmove/memcmp/..., but I
don't think we can do something about malloc.