I am learning NASM and am tying to compile this code (which I found here). It assembles using this NASM command:
nasm -f coff -l printf.lst printf1.asm
to printf.o but this gcc linking command:
gcc -o printf1 printf1.o
fails with the error:
printf1.o:printf1.asm:(.text+0x1a): undefined reference to `printf
collect2: ld returned 1 exit status
What am I doing wrong? Thanks in advance. (EDIT: I m on Windows 7);
; printf1.asm print an integer from storage and from a register
; Assemble: nasm -f coff -l printf.lst printf1.asm
; Link: gcc -o printf1 printf1.o
; Run: printf1
; Output: a=5, eax=7
; Equivalent C code
; /* printf1.c print an int and an expression */
; #include
; int main()
; {
; int a=5;
; printf("a=%d, eax=%d
", a, a+2);
; return 0;
; }
; Declare some external functions
;
extern printf ; the C function, to be called
section .data ; Data section, initialized variables
a: dd 5 ; int a=5;
fmt: db "a=%d, eax=%d", 10, 0 ; The printf format, "
", 0
section .text ; Code section.
global _main ; the standard gcc entry point
_main: ; the program label for the entry point
push ebp ; set up stack frame
mov ebp,esp
mov eax, [a] ; put a from store into register
add eax, 2 ; a+2
push eax ; value of a+2
push dword [a] ; value of variable a
push dword fmt ; address of ctrl string
call printf ; Call C function
add esp, 12 ; pop stack 3 push times 4 bytes
mov esp, ebp ; takedown stack frame
pop ebp ; same as "leave" op
mov eax,0 ; normal, no error, return value
ret ; return