I am beginner in assembly. The following code shows the entire ASM file that I am currently working with.
RegisterClassA does not return NULL because rax is not zero, so I suppose that my WNDCLASSA struct setup is just fine.
My problem occurs when calling CreateWindowExA which returns a NULL HWND. Referring to the CreateWindowExA docs on more error information, I called GetLastError which returned error code 87, which means I input an invalid parameter on CreateWindowExA.
How can I determine what parameter I input wrong? Or perhaps, there is another error that I am not aware of?
ExitProcess proto
MessageBoxA proto
RegisterClassA proto
GetModuleHandleA proto
LoadIconA proto
LoadCursorA proto
GetStockObject proto
CreateWindowExA proto
DefWindowProcA proto
DestroyWindow proto
PostQuitMessage proto
GetLastError proto
.const
w32_class_name byte "snake_asm_window_class", 0
w32_window_name byte "snake", 0
w32_window_width dword 720
w32_window_height dword 1280
.code
WinMainCRTStartup proc
; WNDCLASS Struct: 72 bytes
; 4 Local Vars: 32 bytes
; 8 more params for CreateWindowExA: 64 bytes
; 4 registers: 32 bytes
; 72 + 32 + 64 + 32 = 200 bytes
sub rsp, 200
mov ecx, 4
call GetStockObject
mov qword ptr [rsp + 120], rax
xor rcx, rcx
mov edx, 32512
call LoadIconA
mov qword ptr [rsp + 112], rax
xor rcx, rcx
mov edx, 32512
call LoadCursorA
mov qword ptr [rsp + 104], rax
xor rcx, rcx
call GetModuleHandleA
mov qword ptr [rsp + 96], rax
lea rcx, [rsp + 128] ; WNDCLASS into rcx
mov dword ptr [rcx + 0], 23h ; style = CS_HREDRAW | CS_OWNDC | CS_VREDRAW;
lea rax, [WindowProc]
mov qword ptr [rcx + 8], rax ; lpfnWndProc = WindowProc;
mov dword ptr [rcx + 16], 0 ; WindowClass.cbClsExtra = 0;
mov dword ptr [rcx + 20], 0 ; WindowClass.cbClsExtra = 0;
mov rax, qword ptr [rsp + 96]
mov qword ptr [rcx + 24], rax ; WindowClass.hInstance = ModuleInstance;
mov rax, qword ptr [rsp + 112]
mov qword ptr [rcx + 32], rax ; WindowClass.hIcon = LoadIcon(0, MAKEINTRESOURCE(32512));
mov rax, qword ptr [rsp + 104]
mov qword ptr [rcx + 40], rax ; WindowClass.hCursor = LoadCursor(0, MAKEINTRESOURCE(32512));
mov rax, qword ptr [rsp + 120]
mov qword ptr [rcx + 48], rax ; WindowClass.hbrBackground = GetStockObject(BLACK_BRUSH);
mov qword ptr [rcx + 56], 0 ; WindowClass.lpszMenuName = 0;
lea rax, w32_class_name
mov qword ptr [rcx + 64], rax ; WindowClass.lpszClassName = WindowClassName;
call RegisterClassA
xor ecx, ecx
lea rdx, w32_class_name
lea r8, w32_window_name
mov r9d, 0cf0000h
mov dword ptr [rsp + 32], 0
mov dword ptr [rsp + 40], 0
mov dword ptr [rsp + 48], 1280
mov dword ptr [rsp + 56], 720
mov qword ptr [rsp + 64], 0
mov qword ptr [rsp + 72], 0
mov rax, qword ptr [rsp + 96]
mov qword ptr [rsp + 80], rax
mov qword ptr [rsp + 88], 0
call CreateWindowExA
call GetLastError ; returns error code 87: ERROR_INVALID_PARAMETER
xor rcx, rcx
call ExitProcess
WinMainCRTStartup endp
WindowProc proc
sub rsp, 40
xor rax, rax
test edx, 010h
je WM_CLOSE
call DefWindowProcA
jmp done
WM_CLOSE:
call DestroyWindow
jmp done
done:
add rsp, 40
ret
WindowProc endp
end
what is just visible
test edx, 010h
you want compare message value with WM_CLOSE ( 10h) but instead cmp use test, as result you call DestroyWindow when you really not want and not need . and really not need call DestroyWindow on WM_CLOSE - the DefWindowProcA do this for you. probably you need call PostQuitMessage on WM_NCDESTROY.
then even if CreateWindowExA is ok, you need some message loop after this, but you not do this and call ExitProcess so in any case your program just exit, even if window will be created.
you not use WS_VISIBLE style and not call ShowWindow as result, even if window will be created and messgeloop exist - it will be invisible anyway.
you not check return values of RegisterClassA and CreateWindowExA . and call GetLastError after CreateWindowExA exist sense only if CreateWindowExA return 0.
use WinMainCRTStartup as entry point is ok, but really you can in concrete case use any name, and set this name in /ENTRY:name linker option (now you use default /ENTRY:WinMainCRTStartup )
in general probably no sense write such code complete on asm, use it exist sense only for special task, but minimal visible example can be next
EXTERN __imp_GetStockObject : QWORD
EXTERN __imp_LoadIconA : QWORD
EXTERN __imp_LoadCursorA : QWORD
EXTERN __ImageBase : QWORD
EXTERN __imp_RegisterClassA : QWORD
EXTERN __imp_CreateWindowExA : QWORD
EXTERN __imp_PostQuitMessage : QWORD
EXTERN __imp_ExitProcess : QWORD
EXTERN __imp_GetLastError : QWORD
EXTERN __imp_DefWindowProcA : QWORD
EXTERN __imp_GetMessageA : QWORD
EXTERN __imp_DispatchMessageA : QWORD
.code
Startup proc
; WNDCLASS Struct: 72 bytes
; 4 Local Vars: 32 bytes
; 8 more params for CreateWindowExA: 64 bytes
; 4 registers: 32 bytes
; 72 + 32 + 64 + 32 = 200 bytes
sub rsp, 200
mov ecx, 4
call __imp_GetStockObject
mov qword ptr [rsp + 120], rax
xor rcx, rcx
mov edx, 32512
call __imp_LoadIconA
mov qword ptr [rsp + 112], rax
xor rcx, rcx
mov edx, 32512
call __imp_LoadCursorA
mov qword ptr [rsp + 104], rax
lea rax, __ImageBase
mov qword ptr [rsp + 96], rax
lea rbp, [rsp + 128] ; WNDCLASS into rcx
mov rcx,rbp
mov dword ptr [rcx + 0], 23h ; style = CS_HREDRAW | CS_OWNDC | CS_VREDRAW;
lea rax, [WindowProc]
mov qword ptr [rcx + 8], rax ; lpfnWndProc = WindowProc;
mov dword ptr [rcx + 16], 0 ; WindowClass.cbClsExtra = 0;
mov dword ptr [rcx + 20], 0 ; WindowClass.cbClsExtra = 0;
mov rax, qword ptr [rsp + 96]
mov qword ptr [rcx + 24], rax ; WindowClass.hInstance = ModuleInstance;
mov rax, qword ptr [rsp + 112]
mov qword ptr [rcx + 32], rax ; WindowClass.hIcon = LoadIcon(0, MAKEINTRESOURCE(32512));
mov rax, qword ptr [rsp + 104]
mov qword ptr [rcx + 40], rax ; WindowClass.hCursor = LoadCursor(0, MAKEINTRESOURCE(32512));
mov rax, qword ptr [rsp + 120]
mov qword ptr [rcx + 48], rax ; WindowClass.hbrBackground = GetStockObject(BLACK_BRUSH);
mov qword ptr [rcx + 56], 0 ; WindowClass.lpszMenuName = 0;
lea rax, w32_class_name
mov qword ptr [rcx + 64], rax ; WindowClass.lpszClassName = WindowClassName;
call __imp_RegisterClassA
test ax,ax
je @@2
xor ecx, ecx
lea rdx, w32_class_name
lea r8, w32_window_name
mov r9d, 10cf0000h
mov dword ptr [rsp + 32], 0
mov dword ptr [rsp + 40], 0
mov dword ptr [rsp + 48], 1280
mov dword ptr [rsp + 56], 720
mov qword ptr [rsp + 64], 0
mov qword ptr [rsp + 72], 0
mov rax, qword ptr [rsp + 96]
mov qword ptr [rsp + 80], rax
mov qword ptr [rsp + 88], 0
call __imp_CreateWindowExA
test rax, rax
je @@1
@@0:
mov rcx, rbp
xor rdx,rdx
mov r8,rdx
mov r9,rdx
call __imp_GetMessageA
test eax, eax
je @@2
mov rcx, rbp
call __imp_DispatchMessageA
jmp @@0
@@1:
call __imp_GetLastError ;
@@2:
xor rcx, rcx
call __imp_ExitProcess
Startup endp
WindowProc proc
sub rsp, 28h
cmp edx, 82h ; WM_NCDESTROY
jne @@0
mov [rsp + 30h], rcx
mov [rsp + 38h], rdx
mov [rsp + 40h], r8
mov [rsp + 48h], r9
xor ecx, ecx
call __imp_PostQuitMessage
mov rcx, [rsp + 30h]
mov rdx, [rsp + 38h]
mov r8, [rsp + 40h]
mov r9, [rsp + 48h]
@@0:
call __imp_DefWindowProcA
add rsp, 28h
ret
WindowProc endp
.const
w32_class_name byte "snake_asm_window_class", 0
w32_window_name byte "snake", 0
end
(use /ENTRY:Startup )