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carraysassemblynasm
Mat A
Mat A

Reputation: 151

c pass array to nasm function

I am trying to pass an array to my sorting program written in assembly. The code i have so far is:

main.c:

#include <stdio.h>

extern void myFunc(int * somedata);

int arr[5] = { 3, 2, 33, 11, 1};

void main(){
    int i;
    myFunc(arr);
    for(i = 0; i < 5; i++)
    {
    //      printf( "%d\n", arr[i] );
    }
}

myFunc.asm:

section .text global myFunc extern printf

    myFunc:
            enter   4,0
            push    ebx

            push    dword [ebp + 8]
            call    printf

            pop     ebx
            leave
            ret

This is just some testing code to get learn how to do this.

My understanding would be that this should print the pointer to the array but I'm probably wrong.

Can anyone give me a simple example of passing an array to an assembly file (NASM).

Thank you!

Upvotes: 0

Views: 1522

Answers (2)

vonbrand
vonbrand

Reputation: 11791

The best way to answer such questions is to write a short function that does the types of operations you are interested in in C, and compile that to assembly to do reverse engineering.

Upvotes: 2

Jonathon Reinhart
Jonathon Reinhart

Reputation: 137398

You're calling printf with the first argument being the pointer that was passed to myFunc. That's not going to work - the first argument has to be a format string.

The rest of your code looks okay though. Note, you're going to have to pass the length of the array to your asm function, too.

Upvotes: 2

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