| Issue |
61522
|
| Summary |
UBsan produces incorrect report on a null-pointer-dereference
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
shao-hua-li
|
For the following code, Clang's UBsan cannot produce an incorrect report on the null-pointer-dereference. GCC'UBsan can produce the correct report.
Compiler explorer: https://godbolt.org/z/949vYEaMb
```shell
% cat a.c
struct a {
char d
} ;
struct a b;
struct a *c;
struct a e() {
int f[3];
f[2]=0;
c = 0;
f[2]=0;
*c = b;
return b;
}
void main() {
e();
}
%
% clang -fsanitize=undefined -O0 a.c && ./a.out
UndefinedBehaviorSanitizer:DEADLYSIGNAL
==1==ERROR: UndefinedBehaviorSanitizer: SEGV on unknown address
...
% clang -fsanitize=undefined -O2 a.c && ./a.out
/a.c:8:3: runtime error: subtraction of unsigned offset from 0x7ffcd03c3e2c overflowed to 0x7ffcd03c3e34
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /a.c:8:3 in
/a.c:10:3: runtime error: subtraction of unsigned offset from 0x7ffcd03c3e2c overflowed to 0x7ffcd03c3e34
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /a.c:10:3 in
UndefinedBehaviorSanitizer:DEADLYSIGNAL
==1==ERROR: UndefinedBehaviorSanitizer
...
%
% gcc -fsanitize=undefined -O2 a.c && ./a.out
/a.c:11:6: runtime error: store to null pointer of type 'struct a'
%
```
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