[cfe-dev] trouble getting Hello World / gas / Mac OS X to work

[Andrew Pennebaker]

I'm trying to write Hello World in GNU assembler for Mac OS X, but it's bus
erroring before it can print "Hello World".

hello.s<https://github.com/mcandre/mcandre/blob/master/gas/hello/freebsd/hello.s>
:

.global start

.data

.equ stdout, 1

.equ sys_write, 4
.equ sys_exit, 1

.equ kernel, 0x80

msg: .asciz "Hello World!\n"
.equ len, .-msg

.text

start:
	push $len
	push $msg
	push $stdout
	mov $sys_write, %eax
	sub $4, %esp
	int $kernel
	add $4 + $4 * $3, %esp

	push $0
	mov $sys_exit, %eax
	sub $4, %esp
	int $kernel

Trace:

$ clang -c -o hello.o hello.s
$ ld -o hello -macosx_version_min 10.6 hello.o
$ ./hello
Bus error: 10

$ gdb hello
(gdb) run
Starting program: /Users/andrew/Desktop/src/mcandre/gas/hello/freebsd/hello

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_PROTECTION_FAILURE at address: 0x0000000000002000
0x0000000000002000 in msg ()

I'm basing my code off of a couple things:

   - Working NASM / Mac OS X code for Hello
World<https://github.com/mcandre/mcandre/blob/master/nasm/hello/freebsd/hello.asm>
   - Working Gas / Linux code for Hello
World<https://github.com/mcandre/mcandre/blob/master/gas/hello/linux/hello.s>

I took the semantics from NASM / Mac OS X and the syntax from Gas / Linux.

I also tried the example program on the GNU Assembler Wikipedia
page<http://en.wikipedia.org/wiki/GNU_Assembler#Example_Programs>,
but it also bus error's.

I filed a bug report with Apple due to its GNU assembler being horribly out
of date (as 1.38). They said to use clang instead, so here I am.

What am I doing wrong?

Specs:

* ld64-134.9
* clang 4.1
* Xcode 4.5
* Mac OS X 10.8.2
* MacBook Pro 2009

-- 
Cheers,

Andrew Pennebaker
www.yellosoft.us
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20121015/cb775eb5/attachment.html>