| Issue |
208655
|
| Summary |
[compiler-rt][tysan][libc++] False positives with global/static struct containing STL containers
|
| Labels |
libc++
|
| Assignees |
|
| Reporter |
onurcan-isler-oss
|
# global/static `struct` offset and layout
#### Flags: `-stdlib=libc++ -fsanitize=type -O1`
#### Compiler: x86-64 clang 22.1.0
#### Link: https://godbolt.org/z/x4nM6K5Mv
#### Code:
```.cpp
#include <vector>
struct Registry {
std::vector<int> arr;
char temp_byte;
bool bool_var = false;
};
int main() {
static Registry r;
r.arr.push_back(0); // reserve is also repro
r.bool_var = true;
}
```
#### Logs:
```
==1==ERROR: TypeSanitizer: type-aliasing-violation on address 0x62c0c8b4df08 (pc 0x62c0c81f3179 bp 0x7ffdf94d1420 sp 0x7ffdf94d13b0 tid 1)
WRITE of size 1 at 0x62c0c8b4df08 with type bool (in Registry at offset 32) accesses part of an existing object of type p1 int (in std::__1::vector<int, std::__1::allocator<int>> at offset 0) that starts at offset -32
#0 0x62c0c81f3178 (/app/output.s+0x36178)
```
#### Explanation:
- If we remove the “static” keyword in Registry initialization, it will not reproduce.
- If we replace the vector array with three int pointers, it will not reproduce.
- If we remove the vector function, it will not reproduce.
- If we reorder struct variables it will not reproduce:
```.cpp
#include <vector>
struct Registry {
char temp_byte;
std::vector<int> arr;
bool bool_var = false;
};
int main() {
static Registry r;
r.arr.push_back(0);
r.bool_var = true;
}
```
- Global `struct` also fires:
```.cpp
#include <vector>
struct Registry {
std::vector<int> arr;
char temp_byte;
bool bool_var = false;
};
Registry r;
int main() {
r.arr.push_back(0); // reserve is also repro
r.bool_var = true;
}
```
Might be related to global/static STL containers FP in 20.1.0: https://godbolt.org/z/q3TsrK5c4
But fixed in 22.1.0: https://godbolt.org/z/1qE3z6eea
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