<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/119615>119615</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            TySan doesn't catch strict-aliasing violation when using struct initializers
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            compiler-rt:tysan
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          fhahn
      </td>
    </tr>
</table>

<pre>
    The initial version of TySan (https://github.com/llvm/llvm-project/pull/76261) doesn't properly report the first strict aliasing violation in the test case below


```
#include <stdio.h>

__attribute__((noinline))
void print(char**v) {
    printf("%s\n", v[0]);
}

int main() {
  char *values[2] = { "value", 0};
  void **curr = ((void *) values);
  int count;
  for (count = 0; curr && curr[count]; count++);

  values[0] = "test";
  print(values);
  return count;
}
```
 
Produces the output below with TySan. It looks like it is missing setting the initial type of `values` and the first reported violation is `  values[0] = "test";`, while it should already report the read of `void *` for `curr[count]` from memory with `char *`.

```
> bin/clang -fsanitize=type test.c -O1  -g -isysroot $MACOS_SYSROOT
>  ./a.out
==81689==ERROR: TypeSanitizer: type-aliasing-violation on address 0x00016b16b1c0 (pc 0x000104c97dac bp 0x00016b16b1b0 sp 0x00016b16a940 tid 18058865)
WRITE of size 8 at 0x00016b16b1c0 with type p1 omnipotent char accesses an existing object of type p1 void
    #0 0x000104c97da8 in main test.c:14

==81689==ERROR: TypeSanitizer: type-aliasing-violation on address 0x00016b16b1c0 (pc 0x000104c97a68 bp 0x00016b16b180 sp 0x00016b16a910 tid 18058865)
READ of size 8 at 0x00016b16b1c0 with type p1 omnipotent char accesses an existing object of type p1 void
    #0 0x000104c97a64 in print test.c:5

test
```
</pre>
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