https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95485
Bug ID: 95485
Summary: missing warning writing into function text
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
GCC doesn't diagnose attempts to write into functions, even though those will
in all likelihood crash with a SIGBUS at runtime.
For example, in the following snippet the destination of the memset call is a
function rather than the memory it was called to obtain. The memset call
should be diagnosed.
$ cat z.c && gcc -O2 -S -Wall -fdump-tree-optimized=/dev/stdout z.c
typedef void* F (int);
void* f (F *p)
{
void *q = p (32); // allocate memory
__builtin_memset (p, 0, 32); // zero out -- whoops! -- writing to a
function
return q; // return "clear" memory
}
;; Function f (f, funcdef_no=0, decl_uid=1933, cgraph_uid=1, symbol_order=0)
f (void * (*<T322>) (int) p)
{
void * q;
<bb 2> [local count: 1073741824]:
q_4 = p_2(D) (32);
__builtin_memset (p_2(D), 0, 32);
return q_4;
}
Two compilers on Godbolt diagnose the code: Visual C++:
z.c(8): warning C4152: nonstandard extension, function/data pointer conversion
in expression
and the Small Device C Compiler (SDCC):
x.c:8: warning 244: pointer types incompatible
from type 'void generic* function ( int fixed) code* fixed'
to type 'void generic* fixed'
