如何从程序集中调用C函数

Question

I am programming x86 assembly in Visual Studio 2012.

I'm trying to call printf from an assembly program, but it throws an error as soon as I include the EXTERN line. It's probably something really stupid like including the library of C functions but I can't find any online resource that tells me how to do it right.

Here's my code:

.model flat

            EXTERN  _printf

.data

digits      byte    "0" dup (10), 0         

.code

main proc

            lea     eax,    digits
            push    eax
            call    _printf
            add     esp,    4

main endp

END

And the error thrown is:

error A2008: syntax error : in directive

on line 3 (the line with EXTERN)

EDIT: Added information about environment (the first line).

Answer 1

As commented, use

        extern  _printf:proc

or if 32 bit mode, you may need to use:

        extern  _printf:near

externs may need to be placed in the .code section.

Also add these two lines near the top of your source code to cause the linker to look in these libraries.

        includelib   msvcrtd
        includelib   oldnames