| Issue |
64684
|
| Summary |
Undefined behavior sanitizer missed case with uninitialized arrays
|
| Labels |
enhancement,
compiler-rt:ubsan
|
| Assignees |
|
| Reporter |
wheatman
|
I found this based on reading https://discourse.llvm.org/t/clang-assigning-an-uninitialized-array-to-another-array-produces-undefined-behavior-with-optimization-o1/72763
the following code which I believe is undefined behavior based on
`the value of an object with automatic storage duration is used while it is indeterminate” (C99 draft).`
is not detected by `-fsanitize=undefined,address`
```
#include <stdio.h>
#define N 4
int ia[N];
int main (void) {
int i, ib[N];
for (i = 0; i < N; i++)
ia[i] = ib[i];
/* check results: */
for (i = 0; i < N; i++)
printf("%d : %d\n",ia[i], ib[i]);
return 0;
}
```
The output does change based on optimization levels which indicates to me that this is undefined behavior
https://godbolt.org/z/s9T6TdEbd
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