macOS Assembly syntax?

[SAEinSDSU]

In my assembly programming class and book all of the syntax for assembly has l or q or some other char after the commands such as movl, leaq ect...however when i look up the language and sample codes do not have these char's. Also % signs are used before the registers (e.g. %eax, %edp)...just wondering why this is and what they mean? Thanks!

 

[pilotError]

movl = Move Long word (I'm pretty sure). The others make sense when you learn the registers. dp being some sort of pointer.

Sorry, it's been a while and the cobwebs are pretty thick!

 

[Cromulent]

In my assembly programming class and book all of the syntax for assembly has l or q or some other char after the commands such as movl, leaq ect...however when i look up the language and sample codes do not have these char's. Also % signs are used before the registers (e.g. %eax, %edp)...just wondering why this is and what they mean? Thanks!

If memory serves that is one of the differences between Intel and AT&T syntax.

You might be better off using an assembler like NASM. It has the nicest syntax of any assembler I have seen. While managing to avoid all the rubbish that assemblers like MASM make use of.

 

[Sander]

The suffix is not needed if the assembler can infer the data width from the register name.

 

[SAEinSDSU]

Okay thanks for the clarification on that...now that that is clear here is another inquiry. I wrote this code in assembly using i386 architecture but i keep getting the same compile error.

_main:

.globl _sumthem

_sumthem:

pushl %ebp
movl %esp,%ebp
movl 8(%ebp), %ecx
xorl %esi,%esi
xorl %eax,%eax
again:
addl %esi,%eax
incl %esi
cmpl %esi,%ecx //loop again:
JGE again
popl %ebp
ret


here is the error that xcode keeps giving me

Undefined symbols:
"_main", referenced from:
start in crt1.10.6.o
ld: symbol(s) not found
collect2: ld returned 1 exit status

im not sure what it is talking about when it refers to _main...please let me know

 

[chown33]

It's telling you there isn't a symbol "_main".

Unless I miss my guess, you've neglected to make _main external.

I could easily be wrong, it's been ages since I did any *86 assembler.


Another interpretation is that it's running the final link phase for a stand-alone program, as opposed to a static lib, dylib, or object-file. That's why it's looking for main: it expects you to have defined a main() in your C program (or equivalent). If you don't want an executable program, then you need to tell the linker what you want to produce.


Since you haven't shown the command-line for compiling or assembling, those are just the two best guesses I have.