https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95515
Bug ID: 95515
Summary: missing --Wnonnull on a straightforward call with a
null pointer
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: ---
In the following test case only the first two instances of passing a null
argument to a nonnull function are diagnosed. The third one isn't.
$ cat z.c && gcc -O2 -S -Wall -Wpedantic -fdump-tree-optimized=/dev/stdout z.c
__attribute__ ((nonnull)) void f (void*);
void f1 (void)
{
f (0); // Wnonnull (good)
}
void f2 (void)
{
void *const p = 0;
f (p); // -Wnonnull (good)
}
void f3 (void)
{
void *p = 0;
f (p); // missing -Wnonnull
}
z.c: In function ‘f1’:
z.c:5:3: warning: null argument where non-null required (argument 1)
[-Wnonnull]
5 | f (0); // Wnonnull (good)
| ^
z.c: In function ‘f2’:
z.c:11:3: warning: null argument where non-null required (argument 1)
[-Wnonnull]
11 | f (p); // -Wnonnull (good)
| ^
;; Function f1 (f1, funcdef_no=0, decl_uid=1932, cgraph_uid=1, symbol_order=0)
f1 ()
{
<bb 2> [local count: 1073741824]:
f (0B); [tail call]
return;
}
;; Function f2 (f2, funcdef_no=4, decl_uid=1935, cgraph_uid=2, symbol_order=1)
f2 ()
{
<bb 2> [local count: 1073741824]:
f (0B); [tail call]
return;
}
;; Function f3 (f3, funcdef_no=6, decl_uid=1939, cgraph_uid=3, symbol_order=2)
f3 ()
{
<bb 2> [local count: 1073741824]:
f (0B); [tail call]
return;
}
Clang is similarly ineffective on its own, but its analyzer detects all three:
$ clang -O2 -S -Wall --analyze z.c
z.c:5:3: warning: Null pointer passed as an argument to a 'nonnull' parameter
f (0); // Wnonnull (good)
^~~~~
z.c:11:3: warning: Null pointer passed as an argument to a 'nonnull' parameter
f (p); // -Wnonnull (good)
^~~~~
z.c:18:3: warning: Null pointer passed as an argument to a 'nonnull' parameter
f (p); // missing -Wnonnull
^~~~~
3 warnings generated.
