| Issue |
109777
|
| Summary |
clang does not support union or struct types for "register" variables
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
DavidSpickett
|
Originally reported by https://discourse.llvm.org/t/frontend-how-to-use-register-union-or-struct-in-c/81392.
https://godbolt.org/z/bz8nM1E9x
```
typedef union Test {
int i;
} Test;
register Test t asm ("x21");
typedef struct Test2 {
int i;
} Test2;
register Test t2 asm ("x22");
register int t3 asm ("w23");
register int *t4 asm ("x24");
```
Clang does not allow the first 2, the union and struct, despite their sizeof being correct for the register chosen.
```
<source>:5:22: error: size of register 'x21' does not match variable size
5 | register Test t asm ("x21");
| ^
<source>:5:1: error: bad type for named register variable
5 | register Test t asm ("x21");
| ^
<source>:11:1: error: bad type for named register variable
11 | register Test t2 asm ("w22");
| ^
```
GCC allows all of them.
It appears that types have to be explicitly added, as was done for pointers https://github.com/llvm/llvm-project/commit/2e31e4e47b09ca5e889e7470e5ae372348661692.
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