MASM32 Process32FirstW not working

Question

I've been trying to debug this code. My Process32First function just keep returning an invalid value. I don't know what's wrong with it. Can someone help me in this problem?

include \masm32\include\masm32rt.inc

.data
  err db "Error!",0

.data?
  procData PROCESSENTRY32 <>
  procH HANDLE ?

.code
start:
  lea esi, procData

  push 0
  push TH32CS_SNAPPROCESS
  call CreateToolhelp32Snapshot

  mov procH, eax

  mov procData.dwSize, sizeof PROCESSENTRY32

  push offset procData
  push procH
  call Process32First

  .if eax == 0
    jmp _err
  .endif

  jmp _end


_err:
  push offset err
  call StdOut

_end:
  push 0
  call ExitProcess
end start

This is my latest code.

Answer 1

You're calling Process32FirstW, the Unicode (wide character) version of Process32First. So you need a wide character version of PROCESSENTRY32, where TCHAR is defined as WORD. The windows.inc of the MASM32 SDK doesn't have such a version, but the ANSI version (TCHAR => BYTE). As far as I can see you don't need the Unicode version. Remove the uppercase "W" from Process32FirstW.

If you absolutely want to use the Unicode version, you have to declare a special "PROCESSENTRY32W" structure:

include \masm32\include\masm32rt.inc

PROCESSENTRY32W STRUCT
    dwSize              DWORD ?
    cntUsage            DWORD ?
    th32ProcessID       DWORD ?
    th32DefaultHeapID   DWORD ?
    th32ModuleID        DWORD ?
    cntThreads          DWORD ?
    th32ParentProcessID DWORD ?
    pcPriClassBase      DWORD ?
    dwFlags             DWORD ?
    szExeFile           dw MAX_PATH dup(?)
PROCESSENTRY32W ENDS

.data
    err db "Error!",0

.data?
    procData PROCESSENTRY32W <>
    procH HANDLE ?

.code
start:
    lea esi, procData

    push 0
    push TH32CS_SNAPPROCESS
    call CreateToolhelp32Snapshot

    mov procH, eax

    ;https://msdn.microsoft.com/de-de/library/windows/desktop/ms684834(v=vs.85).aspx
    mov procData.dwSize, sizeof PROCESSENTRY32W

    push offset procData
    push procH
    call Process32FirstW

    .if eax == 0
        jmp _err
    .endif

    printf ("%S\n", OFFSET procData.szExeFile)

    jmp _end


_err:
    push offset err
    call StdOut

_end:
    push 0
    call ExitProcess
end start