| Issue |
61512
|
| Summary |
CSA widen-loop option may lead to false positives arsing from useless for loop
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
Geoffrey1014
|
CSA 's widen-loop option may lead to false positives arsing from useless for loop.
Besides, there is a wrong path note: ` instrument_npd305.c:9:10: note: Value assigned to 'l' `
See it live : https://godbolt.org/z/x9evh8qPv
Compilation options : clang --analyze --analyzer-output text -Xclang -analyzer-config -Xclang widen-loops=true
input:
```c
#include <stdio.h>
unsigned char **a() {
int d =0;
int i;
int *k = &i;
int *j = k;
int *l = j;
for (; d < 7; d++)
printf("NPD_FLAG\n");
0 != l, *l;
}
void main() { a(); }
```
Output:
``` bash
instrument_npd305.c:11:11: warning: Dereference of null pointer (loaded from variable 'l') [core.NullDereference]
0 != l, *l;
^
instrument_npd305.c:15:15: note: Calling 'a'
void main() { a(); }
^~~
instrument_npd305.c:9:3: note: Loop condition is true. Entering loop body
for (; d < 7; d++)
^
instrument_npd305.c:9:3: note: Loop condition is true. Entering loop body
instrument_npd305.c:9:3: note: Loop condition is true. Entering loop body
instrument_npd305.c:9:10: note: Value assigned to 'l'
for (; d < 7; d++)
^
instrument_npd305.c:9:10: note: Assuming 'd' is >= 7
for (; d < 7; d++)
^~~~~
instrument_npd305.c:9:3: note: Loop condition is false. Execution continues on line 11
for (; d < 7; d++)
^
instrument_npd305.c:11:3: note: Assuming 'l' is equal to null
0 != l, *l;
^~~~~~
instrument_npd305.c:11:3: note: Assuming pointer value is null
0 != l, *l;
^~~~~~
instrument_npd305.c:11:11: note: Dereference of null pointer (loaded from variable 'l')
0 != l, *l;
^~
1 warning generated.
```
Deleting the loop which is useless code, NPD warning disappear
See it live : https://godbolt.org/z/b9G9W4oef
```c
#include <stdio.h>
unsigned char **a() {
int d =0;
int i;
int *k = &i;
int *j = k;
int *l = j;
//for (; d < 7; d++)
printf("NPD_FLAG\n");
0 != l, *l;
}
void main() { a(); }
```
Compiling this case without widen-loop options does not results in FP NPD warning.
So, it seems that widen-loop has a negative effect.
See it live :https://godbolt.org/z/sEhq8vMGa
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