_Static_assert not accepted in empty switch/case clause

[joeyye-work]

#include <assert.h>
int main(int x, char **argv)
{
        switch (x) {
                case 1:
                    // x++;  // Uncommenting this will pass
                    _Static_assert(1, "error message");
                    break;
        };
        return x;
}

compiled with clang -c c.c -std=c11
error: expected expression
_Static_assert(1, "error message");

Impacted version: from llvm-14 to llvm-17

Strange thing is if I put some statements before the _Static_assert it will work.

GCC compiles it fine.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Jinyun (Joey) Ye (joeyye-work)

```c #include <assert.h> int main(int x, char **argv) { switch (x) { case 1: // x++; // Uncommenting this will pass _Static_assert(1, "error message"); break; }; return x; } ``` compiled with clang -c c.c -std=c11 error: expected expression _Static_assert(1, "error message");

Impacted version: from llvm-14 to llvm-17

Strange thing is if I put some statements before the _Static_assert it will work.

GCC compiles it fine.

[llvmbot]

@llvm/issue-subscribers-c11

Author: Jinyun (Joey) Ye (joeyye-work)

```c #include <assert.h> int main(int x, char **argv) { switch (x) { case 1: // x++; // Uncommenting this will pass _Static_assert(1, "error message"); break; }; return x; } ``` compiled with clang -c c.c -std=c11 error: expected expression _Static_assert(1, "error message");

Impacted version: from llvm-14 to llvm-17

Strange thing is if I put some statements before the _Static_assert it will work.

GCC compiles it fine.

[AaronBallman]

This isn't valid until C23 because _Static_assert is a declaration, not a statement; we partially implement WG14 N2508 but we don't fully implement it. This is a duplicate of #53692