What are CFI directives in Gnu Assembler (GAS) used for?
- by claws
There seem to be a .CFI directive after every line and also there are wide varities of these ex.,.cfi_startproc , .cfi_endproc etc.. more here.
.file "temp.c"
.text
.globl main
.type main, @function
main:
.LFB0:
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
movq %rsp, %rbp
.cfi_offset 6, -16
.cfi_def_cfa_register 6
movl $0, %eax
leave
ret
.cfi_endproc
.LFE0:
.size main, .-main
.globl func
.type func, @function
func:
.LFB1:
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
movq %rsp, %rbp
.cfi_offset 6, -16
.cfi_def_cfa_register 6
movl %edi, -4(%rbp)
movl %esi, %eax
movb %al, -8(%rbp)
leave
ret
.cfi_endproc
.LFE1:
.size func, .-func
.ident "GCC: (Ubuntu 4.4.1-4ubuntu9) 4.4.1"
.section .note.GNU-stack,"",@progbits
I didn't get the purpose of these.