Writing Intel Syntax in Xcode 10.3

Question

I'm writing a C project in Xcode and I'd like to link a separate assembly file to be compiled along with the project. But I need the assembly to be written in Intel syntax since I find AT&T syntax absolutely grotesque.

Unfortunately, Apple's default Clang compiler doesn't like me writing my assembly code in Intel and prefers AT&T. Is there a setting I can change to allow my separate assembly file to be written in Intel syntax?

As an example, this assembles:

.text  
.global _func  
func:  
mov %rdx,%rax  
ret

But this doesn't assemble

.text  
.global _func  
_func:  
mov rax,rdx  
ret

The compiler throws errors with the latter example.

_func Is being called from the C code.

#include <stdio.h>
void func(void);
int main(int argc, const char * argv[]) {
    func();
    return 0;
}

To clarify, I am not writing inline assembly.

score 3 · Accepted Answer · answered Aug 22 '19 at 01:40

3

If you want to use asm intel syntax. Just add .intel_syntax noprefix to begin of asm file.

.intel_syntax noprefix
.text  
.global _func  
_func:  
mov rax,rdx  
ret

answered Aug 22 '19 at 01:40

Thanh Vu

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14

Ah thank you! That works. What is the noprefix for? – Irelia Aug 22 '19 at 01:57
I think `noprefix` is disable prefix in assembly intruction. – Thanh Vu Aug 22 '19 at 02:06
2

@Nina: `noprefix` lets you write `rax` instead of `%rax` for register names, controlled separately from the rest of Intel vs. AT&T syntax mode. – Peter Cordes Aug 22 '19 at 09:35
@PeterCordes You are right. Link: http://web.mit.edu/rhel-doc/3/rhel-as-en-3/i386-syntax.html – Thanh Vu Aug 22 '19 at 09:39
@PeterCordes Interesting. I assumed intel syntax alone meant I didn't need the % before registers. Thanks for clarifying. – Irelia Aug 22 '19 at 12:02

Writing Intel Syntax in Xcode 10.3

1 Answers1