Limitations of Intel Assembly Syntax Compared to AT&T

Linux Problem Overview

To me, Intel syntax is much easier to read. If I go traipsing through assembly forest concentrating only on Intel syntax, will I miss anything? Is there any reason I would want to switch to AT&T (outside of being able to read others' AT&T assembly)? My first clue is that gdb uses AT&T by default.

If this matters, my focus is only on any relation assembly and syntax may have to Linux/BSD and the C language.

Linux Solutions

Solution 1 - Linux

There is really no advantage to one over the other. I agree though that Intel syntax is much easier to read. Keep in mind that, AFAIK, all GNU tools have the option to use Intel syntax also.

It looks like you can make GDB use Intel syntax with this:

set disassembly-flavor intel

GCC can do Intel syntax with -masm=intel.

Solution 2 - Linux

The primary syntax for the GNU assembler (GAS) is AT&T. Intel syntax is a relatively new addition to it. x86 assembly in the Linux kernel is in AT&T syntax. In the Linux world, it's the common syntax. In the MS world, Intel syntax is more common.

Personally, I hate AT&T syntax. There are plenty of free assemblers (NASM, YASM) along with GAS that support Intel syntax too, so there won't be any problems doing Intel syntax in Linux.

Beyond that, it's just a syntactic difference. The result of both will be the same x86 machine code.

Solution 3 - Linux

There is really no advantage to one over the other. I disagree though that Intel syntax is much easier to read, because personally I hate Intel syntax. Keep in mind that, AFAIK, all GNU tools have the option to use Intel syntax also.

at&t noprefix                   intel
mov eax, -4(ebp,edx,4)          mov DWORD PTR[-4 +ebp +edx *4], eax
mov eax, -4(ebp)                mov DWORD PTR[-4 +ebp], eax
mov edx, (ecx)                  mov DWORD PTR[ecx], edx
lea (   ,eax,4), eax            lea eax, DWORD PTR[8 + eax*4]
lea (eax,eax,2), eax            lea eax, DWORD PTR[eax*2+eax]

...and it gets more complicated with more complex instructions

'nuff said.

PS: This answer exists mainly for the reason of highlighting (IMHO) weaknesses in some other answers, which are actually not answers, but opinions. And of course this answer in reality is only my humble opinion.

PPS: I do not hate Intel syntax, I just don't care.

Solution 4 - Linux

It's the "same language", in that it compiles down to the same machine code, has the same opcodes, etc. On the other hand, if you are using GCC at all, you will probably want to learn AT&T syntax, just because it's the default--no changing compiler options, etc. to get it.

I too cut my teeth on Intel-syntax x86 ASM (on DOS, too) and found it more intuitive initially when switching to C/UNIX. But once you learn AT&T it'll look just as easy.

I wouldn't give it that much thought---it's easy to learn AT&T once you know Intel, and vice-versa. The actual language is much harder to get in your head than the syntax. So by all means just focus on one and then learn the other when it comes up.

Solution 5 - Linux

It's a sign of professionalism that you are willing to adjust to whatever is in use. There is no real advantage to one or the other. The intel syntax is common in the Microsoft world, AT&T is the standard in Linux/Unix. Since there's no advantage to either one, people tend to imprint on whatever they saw first. That said, a professional programmer raises above things like that. Use whatever they use at work, or in the domain that you're working in.

Solution 6 - Linux

Intel syntax covers everything (assuming the assembler/disassembler is up to date with the latest junk Intel added to their instruction set). I'm sure at&t is the same.

at&t                             intel
movl -4(%ebp, %edx, 4), %eax     mov eax, [ebp-4+edx4]
movl -4(%ebp), %eax              mov eax, [ebp-4]
movl (%ecx), %edx                mov edx, [ecx]
leal 8(,%eax,4), %eax            lea eax, [eax4+8]
leal (%eax,%eax,2), %eax         lea eax, [eax*2+eax]