How to use C functions in asm?

LongName · 08-28-2004, 03:22 PM

Im using nasm as an asm compiler and gcc/g++ for c/c++ compiling.

I have a C function in file1.c and some code in asm in file2.asm. How may I call the function in file1.c from file2.asm?

Thanks in advance!

infamous41md · 08-28-2004, 03:58 PM

Code:

[n00b@localho.outernet] cat test.c
int foo()
{
    printf("foobar\n");
}
[n00b@localho.outernet] cat test.s

.text

.global foo

.global _start

_start:

    call foo
    movl $1, %eax
    int $0x80
[n00b@localho.outernet] gcc test.c test.s -nostartfiles
[n00b@localho.outernet] ./a.out 
foobar

LongName · 08-28-2004, 06:13 PM

Thanks very much!

When linking using ld, I get an error stating that there is an undefined reference to 'printf', I have included <stdio.h> in file1.c. What may/am I (be) missing?

Thanks in advance!

infamous41md · 08-28-2004, 07:56 PM

you need to link with libc. read the man page for 'ld' and it will tell you how to link with libraries on the command line.

LongName · 08-29-2004, 12:25 AM

Thanks very much!

Everything works now