Question

I am trying just to print out the value of argc using the CommandLineToArgvW Window’s API function in NASM. The following is what I have:

extern _ExitProcess@4
extern _GetCommandLineA@0
extern _CommandLineToArgvW@8
extern printf

global _start
section .code

Format:
    db "%d",10,0
FormatS:
    db "%s",10,0
_start:
    push ebp
    mov ebp, esp
    sub esp, 4 ; Create empty space for ArgC
    call _GetCommandLineA@0
    push eax; Push value beneath ArgC
    mov ebx, ebp ; Set ebx to ebp
    sub ebx, 4
    push dword ebx ; pushes ArgC address onto stack
    push dword [ebp - 8] ; pushes pointer to Command Line String
    call _CommandLineToArgvW@8
    push dword [ebp - 4]
    push Format
    call printf
    push dword 0
    call _ExitProcess@4

No matter what I do, the value for argc is 1. What am I doing wrong?

I assemble and link with these commands:

nasm -fwin32 FunctionTests.asm
golink FunctionTests.obj kernel32.dll msvcrt.dll shell32.dll /console /entry _start
FunctionTests.exe hi asdf asdf asdf asdf

As you can see, from the last line, argc should be 6.

Answer 1

Change _GetCommandLineA to _GetCommandLine*W* CommandLineToArgv expects a pointer to a UNICODE string.

MASM but just about the same:

start:
    push    ebp
    mov     ebp, esp
    sub     esp, 4

    call    GetCommandLineW

    lea     ecx, dword ptr[ebp - 4] ; need the address of local
    push    ecx                     ; address of local
    push    eax                     ; pointer to unicode string
    call    CommandLineToArgvW

    push    dword ptr [ebp - 4]     ; value of local
    push    offset Format
    call    crt_printf
    add     esp, 8

    ; this is all?  Then we don't have to restore stack.
    push    0
    call    ExitProcess
end start

and this is the output:

D:\Projects>ConTest.exe boo boo I see you

6

D:\Projects>