C float in NASM x86 assembly -

in university project have use binary representation of float number in x86 assembly arithmetic operations. using fpu forbidden try read float number , return dword whatever try "-nan". advices?

edit: use gcc , it's 32 bit code

declaration in c (i can't change that)

extern "c" float func(float num); 

*.asm file

section .text global  func  func: ;prolog     push    ebp     mov ebp, esp  ; zapamiętanie rejestrów zachowywanych     push ebx     push esi     push edi      mov eax, dword [ebp+8]     ;mov eax, 0xffffffff checked still same result  ; odtworzenie rejestrów, które były zapamiętane     pop edi     pop esi     pop ebx  ;epilog      pop ebp     ret 

example result (for 256)

01000011100000000000000000000000 11111111110000000000000000000000 num1: 256.000000 num2: -nan 

edit:

c code without checking bits part

#include <stdio.h>  extern "c" float func(float num);  int main() {     float num1;     float num2;      scanf("%f", &num1);     num2=func(num1);      printf("num1: %f\nnum2: %f\n", num1, num2);     return 0; } 

if declare return type func float result returned in fpu (st0). returning value in eax have declare integer type. printf have fake float. example:

caller.c:

#include <stdio.h> #include <stdint.h> extern float asmfunc1(float); extern uint32_t asmfunc2(float);  int main (void) {     printf ("asmfunc1: %f\n", asmfunc1(456.78));      uint32_t ifl = asmfunc2(123.45);     float* pfl = (float*) &ifl;             // faking float     printf ("asmfunc2: %f\n", *pfl);      return 0; } 

callee.asm:

section .text global asmfunc1, asmfunc2  asmfunc1:     fld dword [esp+4]     ret  asmfunc2:     push ebp     mov ebp, esp     mov eax, [ebp+8]     leave     ret 

build & run:

nasm -felf callee.asm gcc -m32 callee.o caller.c ./a.out