https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107289
Geoffrey <geoffreydgr at icloud dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |geoffreydgr at icloud dot com
--- Comment #3 from Geoffrey <geoffreydgr at icloud dot com> ---
(In reply to David Malcolm from comment #2)
> I believe that the analyzer is considering the case where "d" is (somehow)
> called from outside of "main", and thus not making the assumption that *b ==
> &a; seeing the compare with NULL, it considers the case that b could be NULL.
>
> It's not yet clear to me that this case of d being called from outside
> "main" is valid, or if it's always the case that d can only ever be called
> from main.
In addition, i changed the original case to the following one (only add
specifier static to `d`) and Compiled it with gcc 12.1 with `-O0 -fanalyzer`
```
int a=1;
int *b = &a;
void c () {
int f;
f = *b;
}
void e (){
if (0 == b){
int *g = 0;
}
}
static void d() {
e();
c();
}
int main(){
d();
}
```
results in:
```
<source>: In function 'void c()':
<source>:5:7: warning: dereference of NULL 'b' [CWE-476]
[-Wanalyzer-null-dereference]
5 | f = *b;
| ~~^~~~
'void d()': events 1-2
|
| 12 | static void d() {
| | ^
| | |
| | (1) entry to 'd'
| 13 | e();
| | ~~~
| | |
| | (2) calling 'e' from 'd'
|
+--> 'void e()': events 3-6
|
| 7 | void e (){
| | ^
| | |
| | (3) entry to 'e'
| 8 | if (0 == b){
| | ~~
| | |
| | (4) following 'true' branch...
| 9 | int *g = 0;
| | ~
| | |
| | (5) ...to here
| | (6) 'b' is NULL
|
<------+
|
'void d()': events 7-8
|
| 13 | e();
| | ~^~
| | |
| | (7) returning to 'd' from 'e'
| 14 | c();
| | ~~~
| | |
| | (8) calling 'c' from 'd'
|
+--> 'void c()': events 9-10
|
| 3 | void c () {
| | ^
| | |
| | (9) entry to 'c'
| 4 | int f;
| 5 | f = *b;
| | ~~~~~~
| | |
| | (10) dereference of NULL 'b'
|
```
Static analyzer should not give the CWE-476 warning, and it should start
analyzing from function main instead of function `d` because function `d` is a
static function (it is visible only in this compile unit) and only called by
function `main`.
And i am wondering how gcc analyzer handles global variables?
