https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107736
Bug ID: 107736
Summary: call to a function, generated by inline asm, is off by
one byte
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: miladfarca at gmail dot com
Target Milestone: ---
Tested on Arm64, PPC64 and s390x with gcc 12.
```
const char num = 0;
void call();
asm( ".globl call \n"
".type call, %function \n"
".hidden call \n"
"call: \n"
// Just return.
"ret \n");
int main(){
call();
return 0;
}
```
TL;DR:
The instruction generated for `call();` is jumping to the address of `num` and
causing a crash as `num` is not an instruction, seems to be an alignment issue?
Details:
- This doesn't happen on x64 and call is made to the correct address. It also
does not happen with clang on either platforms (tested with version 6.0).
- gcc is putting "call" into .rodata section of memory including on x64. Not
sure if this is a separate bug or intentional. clang is putting it under
".text" as expected.
- gcc is incorrectly assuming `&num` is the address of `call` and jumping to it
which is off by 1 byte.
- Workarounds include adding either ".text \n" or ".align 8" to the inline asm,
tho call should be made to the correct address even without them?
