| Issue |
136292
|
| Summary |
analyzer: Thinks result of `__builtin_mul_overflow` can be uninitialized
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
Zentrik
|
```c++
#include <stddef.h>
int test(size_t nel, size_t elsz) {
size_t nbytes;
int overflow = __builtin_mul_overflow(nel, elsz, &nbytes);
int overflow2 = __builtin_add_overflow(nel, nbytes, &nbytes);
return overflow * overflow2;
}
```
```
> clang++ --analyze -Xclang -analyzer-output=text -std=c++20
clang++: warning: argument unused during compilation: '-S' [-Wunused-command-line-argument]
<source>:6:19: warning: 2nd function call argument is an uninitialized value [core.CallAndMessage]
6 | int overflow2 = __builtin_add_overflow(nel, nbytes, &nbytes);
| ^ ~~~~~~
<source>:4:3: note: 'nbytes' declared without an initial value
4 | size_t nbytes;
| ^~~~~~~~~~~~~
<source>:5:18: note: Assuming overflow
5 | int overflow = __builtin_mul_overflow(nel, elsz, &nbytes);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:6:19: note: 2nd function call argument is an uninitialized value
6 | int overflow2 = __builtin_add_overflow(nel, nbytes, &nbytes);
| ^ ~~~~~~
1 warning generated.
Compiler returned: 0
```
Godbolt: https://godbolt.org/z/4q4Efcax8
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