| Issue |
175639
|
| Summary |
clang-analyzer-unix.Malloc false positive
|
| Labels |
false-positive
|
| Assignees |
|
| Reporter |
nick-potenski
|
Using the following code to determine the allocation size for a struct containing a flexible array member leads to false-positives from the clang-analyzer-unix.Malloc checker.
```c
#include <stdlib.h>
typedef struct {
size_t count;
int flex_array[];
} flex_array_struct;
int main() {
flex_array_struct* p = (flex_array_struct*)malloc(
(size_t)(&(((flex_array_struct*)0)->flex_array[42])));
p->count = 42;
free(p);
return 0;
}
```
```
<source>:11:14: warning: Use of memory allocated with size zero [clang-analyzer-unix.Malloc]
9 | flex_array_struct* p = (flex_array_struct*)malloc(
| ~~~~~~~
10 | (size_t)(&(((flex_array_struct*)0)->flex_array[42])));
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
11 | p->count = 42;
| ^
<source>:9:48: note: Memory is allocated
9 | flex_array_struct* p = (flex_array_struct*)malloc(
| ^~~~~~~
10 | (size_t)(&(((flex_array_struct*)0)->flex_array[42])));
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:11:14: note: Use of memory allocated with size zero
9 | flex_array_struct* p = (flex_array_struct*)malloc(
| ~~~~~~~
10 | (size_t)(&(((flex_array_struct*)0)->flex_array[42])));
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
11 | p->count = 42;
| ^
1 warning generated.
```
See https://godbolt.org/z/zKKxWxrsM.
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