Mac OS ? Assembly Language Esoteria
- by veryfoolish
I've been playing around with assembly and object files in general on Mac OS ? and was wondering if somebody could provide some edification. Specifically, I'm wondering what the extra code GCC generates when compiling the C file in the following example does.
I have a toy C program so I can comprehend the assembly output.
int main() {
int a = 5;
int b = 5;
int c = a + b; }
Running this through gcc -S creates the following assembly:
.text
.globl _main
_main:
LFB2:
pushq %rbp
LCFI0:
movq %rsp, %rbp
LCFI1:
movl $5, -4(%rbp)
movl $5, -8(%rbp)
movl -8(%rbp), %eax
addl -4(%rbp), %eax
movl %eax, -12(%rbp)
leave
ret
LFE2:
.section __TEXT,__eh_frame,coalesced,no_toc+strip_static_syms+live_support
EH_frame1:
.set L$set$0,LECIE1-LSCIE1
.long L$set$0
LSCIE1:
.long 0x0
.byte 0x1
.ascii "zR\0"
.byte 0x1
.byte 0x78
.byte 0x10
.byte 0x1
.byte 0x10
.byte 0xc
.byte 0x7
.byte 0x8
.byte 0x90
.byte 0x1
.align 3
LECIE1:
.globl _main.eh
_main.eh:
LSFDE1:
.set L$set$1,LEFDE1-LASFDE1
.long L$set$1
LASFDE1:
.long LASFDE1-EH_frame1
.quad LFB2-.
.set L$set$2,LFE2-LFB2
.quad L$set$2
.byte 0x0
.byte 0x4
.set L$set$3,LCFI0-LFB2
.long L$set$3
.byte 0xe
.byte 0x10
.byte 0x86
.byte 0x2
.byte 0x4
.set L$set$4,LCFI1-LCFI0
.long L$set$4
.byte 0xd
.byte 0x6
.align 3
LEFDE1:
.subsections_via_symbols
The LCFI1 section seems to contain the actual logic for the program, but I'm not sure what the misc. other stuff is for... also, is there any scheme these labels are following?
I'm sorry this is such a vague question. I'd appreciate anything, including being pointed to a resource where I can find out more about this. Thanks!
