Thread: How would these variables get pushed on to the stack?

Originally Posted by I C everything

its two different animals compile for x86 or compile for x64 using very different calling conventions
so x64 only uses stack in exceptions
x86 calling conventions - Wikipedia

Yep... Try to compile the same code for i386 (or x86, as you called) and you'll get:

Code:

  section .text

_multiplyByTwo:
  fld QWORD [esp+4]
  fadd  st, st(0)
  ret

  section .rdata
LC2:
  db `double your salary is %.3f\n`, 0

  section .text

  extern printf

  global _main
_main:
  push  ebp
  mov   ebp, esp
  and   esp, -16
  sub   esp, 16
  call  ___main
  mov   DWORD [esp+4], -1030792151
  mov   DWORD [esp+8], 1087904981
  mov   DWORD [esp], .LC2
  call  _printf
  xor   eax, eax
  leave
  ret

_multiplyByTwo isn't called by _main and the direct doubled value is pushed before printf. No 'local vars' are pushed!

Let's try with ARM AArch32, shall we?

Code:

  .cpu cortex-a53
  .arm
  .fpu vfp

  .section .text

  .extern printf

multiplyByTwo:
  vadd.f64  d0, d0, d0
  bx        lr

  .global  main
main:
  push  {r4, lr}
  movw  r0, #:lower16:.LC1
  movt  r0, #:upper16:.LC1
  movw  r2, #23593
  movt  r2, 49807
  movw  r3, #7381
  movt  r3, 16600
  bl    printf  
  mov   r0, #0  
  pop   {r4, pc}

  .section  .rodata 
.LC1:
  .ascii  "double your salary is %.3f\012\000"

Still... no multiplyByTwo call and still no 'local var' pushing...