osx - CoreFoundation functions in Mac OS X Assembly -

i have following code in assembly (assembled clang)

updated thought cause alignment; still doesn't.

updated again; code still seg faults suggestions(thank suggestions though stephen canon ) tried subtract 4, 8, 12 didn't work same stack realignment issue updated more info.

.globl _main .data _hw:    .asciz  "hello world\n\0"  .text _main:  push 8      # 4 bytes push _hw    # 4 bytes push 0      # 4 bytes ##https://developer.apple.com/library/mac/documentation/corefoundation/reference/cfstringref/reference/reference.html#//apple_ref/c/func/cfstringcreatewithcstring call _cfstringcreatewithcstring # 4 bytes ## push cfstr return value in eax sub esp, 8  # 8 bytes push eax    # 4 bytes ##https://developer.apple.com/library/ios/documentation/corefoundation/reference/cftyperef/reference/reference.html#//apple_ref/c/func/cfshow call _cfshow # 4 bytes add esp, 8 # remove padding stack pointer mov eax, 99 ret 

program execution

start of main stack empty

=============== (0xffff) |             | |    stack    | |             | =============== 

the push 8, address of _hw, , 0 call _cfstringcreatewithcstring. looks like

=============== (0xffff) |      8      | |-------------- (0xfffb) 4 bytes 8 |  hw address | |-------------- (0xfff7) 4 bytes address of hw |      0      | |-------------- (0xfff3) 4 bytes 0 (null) |    call     | --------------- (0xffef) 4 bytes address return after call (eip?) 8 on x64? 

then cfstringcreatewithcstring called saving return address (popping off call correct?), popping arguments off stack , jumping saved eip address after executing , putting return value in eax.

after stack looks like

===============  0xffff |             | |    stack    | |             | =============== 

i subtract 8 esp looks like

=============== (0xffff) |   padding   | |   8 bytes   | |-------------- (0xfff7) (esp) |             | =============== 

i push eax cfstringcreatewithcstring stack looks like

=============== (0xffff) |   padding   | |   8 bytes   | |-------------- (0xfff7) # 8 bytes padding subtracting stack counter |     eax     | |-------------- (0xfff3) # 4 bytes eax, return last call, or 8 bytes on x64? |    call     | |-------------- (0xffef) # 4 bytes return after call (eip?) =============== 

after call cfshow (and popping off arguments , address call) stack looks this

=============== (0xffff) |   padding   | |   8 bytes   | |-------------- (0xfff7) # 8 bytes padding subtracting stack counter, cfshow doesn't touch expects 4 byte address  

i add 8 bytes esp removing padding looks this

=============== (0xffff) |             | |    stack    | |             | =============== 

correct?

this type run code, need change because processor 64 bit?

macbookpro:helloworld user$ cat hand.s .globl _main .data _hw:    .asciz  "hello world\n\0"  .text _main:  push 8      # 4 bytes push _hw    # 4 bytes push 0      # 4 bytes call _cfstringcreatewithcstring ## push cfstr return value in eax sub esp, 8  # 8 bytes push eax    # 12 bytes call _cfshow mov eax, 99 ret 

my compilation steps, using clang's built in assembler (gas think) , ld. on mac os x 64 bit mountain lion

macbookpro:helloworld user$ clang -cc1as -filetype obj -mllvm --x86-asm-syntax=intel -o hand.o hand.s 

link corefoundation

macbookpro:helloworld user$ ld -macosx_version_min 10.8.0 -o hand hand.o -lsystem -framework corefoundation 

run executable.

macbookpro:helloworld user$ ./hand segmentation fault: 11 macbookpro:helloworld user$  

results in following error

segmentation fault: 11 

i can't test code , not familiar assembly syntax, seems wrong me...

imho, proper code should be:

.globl _main .data _hw:    .asciz  "hello world\n\0"  .text _main:           push  8         push  _hw       push  0         call  _cfstringcreatewithcstring       add   esp, 12  ; remove arguments stack...      sub   esp, 8   ; align stack next call...      push  eax      call  _cfshow      add   esp, 12      mov   eax, 99     ret 

note, add/sub sequence:

    add   esp, 12  ; remove arguments stack...      sub   esp, 8   ; align stack next call... 

i wrote way in order clean logic, of course can reduced to:

    add   esp, 4  

so, final code:

.globl _main .data _hw:    .asciz  "hello world\n\0"  .text _main:           push  8         push  _hw       push  0         call  _cfstringcreatewithcstring       add   esp, 4   ; clean arguments , align stack next call...      push  eax      call  _cfshow      add   esp, 12      mov   eax, 99     ret