Programming Forums > Application Development > Assembly

Klarre · Mar 3rd, 2008, 2:34 PM

Hi!

I am working on a system managing key presses in a MASM application. The problem is that I must be doing something wrong with the array that keeps the press status of each key. (bool g_keys[256] // Position 0x20 means VK_SPACE i e.)

The "input_set_key" function always returns a non-zero value like my memset hasn't done anything with the array.

What can be the problem? I can't see it...
Thanks alot for your helpfulness!

/Klarre

(Toggle Plain Text)

.data

g_keys dd 0	; Pointer to the array of keys

.code

; ------------------------------------------------------------------------------
input_create proc
	invoke crt_malloc, 256	; Allocate 256 Bytes for the key array
	mov g_keys, eax	; Store the key array pointer

	invoke crt_memset, g_keys, 0, 256	; Make sure no buttons are pressed

	invoke input_is_key_pressed, 27	; DEBUG TEST. Returns a non-zero value

	xor eax, eax

	ret
input_create endp

; ------------------------------------------------------------------------------
input_is_key_pressed proc key:dword
	lea eax, [g_keys]	; Get the key array address
	add eax, key	; Offset to the correct position in the array
	mov eax, [eax]		; Read the value on the position in the array

	ret
input_is_key_pressed endp

end

Klarre · Mar 3rd, 2008, 3:21 PM

After finding the "Memory" debug window in Visual Studio, it was pretty simply to solve the bug. The functions is now looking like this and seems to work fine.

(Toggle Plain Text)

; ------------------------------------------------------------------------------
input_create proc
	invoke crt_malloc, 256	; Allocate 256 Bytes for the key array
	mov g_keys, eax	; Store the key array pointer

	invoke crt_memset, g_keys, 0, 256	; Make sure no buttons are pressed

	ret
input_create endp

; ------------------------------------------------------------------------------
input_is_key_pressed proc key:dword
	mov eax, g_keys	; Get the key array address
	add eax, key	; Offset to the correct position in the array
	mov ah, [eax]	; Read the value on the position in the array

	.if(ah)
		mov eax, 1
	.else
		mov eax, 0
	.endif

	ret
input_is_key_pressed endp

Irwin · Mar 9th, 2008, 7:24 AM

(Toggle Plain Text)

IsKeyPressed proc Key:DWORD
    mov   ecx, [dwKey]
    movzx eax, byte [gKeys+ecx]
    test  eax, eax
    sete  al
    ret
IsKeyPressed endp

InputCreate  proc
    push  256d
    push  GPTR ; memory is filled with 0's
    call  GlobalAlloc
    push  27d
    push  IsKeyPressed
    ret
InputCreate endp

Also, a word to the wise. Don't use MSVCRT in ASM, it completely destroys the purpose of using ASM. The converting is fairly easy too:

malloc -> GlobalAlloc
memset -> stosb/stosw/stosd/stosq

Klarre · Mar 9th, 2008, 1:55 PM

Thanks for your input Irwin. I removed the msvcrt dependency from my project and changed the malloc function call to HeapAlloc since I read on MSDN that GlobalAlloc wasn't recommended.

Another question you may be able to answear on: Is it possible to link a program using the Visual Studio linker without linking with msvcrt.lib? I have set the entry point to main, but still got two linker errors I can't get rid of. So I guess it is impossible, right?

(Toggle Plain Text)

Error	1	error LNK2001: unresolved external symbol __RTC_Shutdown	main.obj
Error	2	error LNK2001: unresolved external symbol __RTC_InitBase	main.obj

Irwin · Mar 10th, 2008, 2:30 AM

Quote:

Originally Posted by Klarre

Thanks for your input Irwin. I removed the msvcrt dependency from my project and changed the malloc function call to HeapAlloc since I read on MSDN that GlobalAlloc wasn't recommended.

Another question you may be able to answear on: Is it possible to link a program using the Visual Studio linker without linking with msvcrt.lib? I have set the entry point to main, but still got two linker errors I can't get rid of. So I guess it is impossible, right?

(Toggle Plain Text)

Error	1	error LNK2001: unresolved external symbol __RTC_Shutdown	main.obj
Error	2	error LNK2001: unresolved external symbol __RTC_InitBase	main.obj

HeapAlloc is only recommended for small buffers, so for anything from 64-1024 bytes I use GlobalAlloc (then use VirtualAlloc for anything larger). Anyway, for a function like GetKeyboardState (which I assume you're using), I would use GlobalAlloc.

Also, you can completely remove any CRT dependency from an application by adding the /NODEFAULTLIB linker flag, then coupling it with the /entry:main (or whatever your entry function is called).

Klarre · Mar 10th, 2008, 5:02 AM

Ah, I see. Going to read up a little bit about the alloc functions.

I am using the /NODEFAULTLIB linker flag and have set the entry point. But this will not get rid of the linker errors...

Irwin · Mar 10th, 2008, 6:51 AM

Quote:

Originally Posted by Klarre

Ah, I see. Going to read up a little bit about the alloc functions.

I am using the /NODEFAULTLIB linker flag and have set the entry point. But this will not get rid of the linker errors...

Post your complete source and assembler/link flags and I'll find your problem.

Klarre · Mar 10th, 2008, 7:23 AM

The source file:

(Toggle Plain Text)

int main() { return 0; }

The linker command line (debug configuration):

(Toggle Plain Text)

/OUT:"G:\workspace\linktest\linktest\Debug\linktest.exe" /INCREMENTAL /NOLOGO /MANIFEST /MANIFESTFILE:"Debug\linktest.exe.intermediate.manifest" /NODEFAULTLIB /SUBSYSTEM:CONSOLE /ENTRY:"main" /MACHINE:X86 /ERRORREPORT:PROMPT

Causes these errors:

(Toggle Plain Text)

1>Linking...
1>main.obj : error LNK2001: unresolved external symbol __RTC_Shutdown
1>main.obj : error LNK2001: unresolved external symbol __RTC_InitBase
1>G:\workspace\linktest\linktest\Debug\linktest.exe : fatal error LNK1120: 2 unresolved externals

The linker command line (release configuration):

(Toggle Plain Text)

/OUT:"G:\workspace\linktest\linktest\Release\linktest.exe" /INCREMENTAL:NO /NOLOGO /MANIFEST /MANIFESTFILE:"Release\linktest.exe.intermediate.manifest" /NODEFAULTLIB /SUBSYSTEM:CONSOLE /OPT:REF /OPT:ICF /LTCG /ENTRY:"main" /MACHINE:X86 /ERRORREPORT:PROMPT

Causes these errors:

(Toggle Plain Text)

1>Linking...
1>main.obj : error LNK2001: unresolved external symbol @__security_check_cookie@4
1>G:\workspace\linktest\linktest\Release\linktest.exe : fatal error LNK1120: 1 unresolved externals

Klarre · Mar 10th, 2008, 10:40 AM

Oh, I meant in a C++ project, which I forgot to mention in the earlier posts.

Irwin · Mar 10th, 2008, 10:41 AM

Oh, the problems aren't in your linking flags but rather your compiler flags. Just add /GS- to your compiler flags.

Good luck

Also, it's fine; I also code in C(++)

Mar 3rd, 2008, 2:34 PM	#1
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 297 Rep Power: 4	[MASM32] Working with arrays Hi! I am working on a system managing key presses in a MASM application. The problem is that I must be doing something wrong with the array that keeps the press status of each key. (bool g_keys[256] // Position 0x20 means VK_SPACE i e.) The "input_set_key" function always returns a non-zero value like my memset hasn't done anything with the array. What can be the problem? I can't see it... Thanks alot for your helpfulness! /Klarre (Toggle Plain Text) .data g_keys dd 0 ; Pointer to the array of keys .code ; ------------------------------------------------------------------------------ input_create proc invoke crt_malloc, 256 ; Allocate 256 Bytes for the key array mov g_keys, eax ; Store the key array pointer invoke crt_memset, g_keys, 0, 256 ; Make sure no buttons are pressed invoke input_is_key_pressed, 27 ; DEBUG TEST. Returns a non-zero value xor eax, eax ret input_create endp ; ------------------------------------------------------------------------------ input_is_key_pressed proc key:dword lea eax, [g_keys] ; Get the key array address add eax, key ; Offset to the correct position in the array mov eax, [eax] ; Read the value on the position in the array ret input_is_key_pressed endp end .data g_keys dd 0 ; Pointer to the array of keys .code ; ------------------------------------------------------------------------------ input_create proc invoke crt_malloc, 256 ; Allocate 256 Bytes for the key array mov g_keys, eax ; Store the key array pointer invoke crt_memset, g_keys, 0, 256 ; Make sure no buttons are pressed invoke input_is_key_pressed, 27 ; DEBUG TEST. Returns a non-zero value xor eax, eax ret input_create endp ; ------------------------------------------------------------------------------ input_is_key_pressed proc key:dword lea eax, [g_keys] ; Get the key array address add eax, key ; Offset to the correct position in the array mov eax, [eax] ; Read the value on the position in the array ret input_is_key_pressed endp end __________________ http://www.klarre.se Last edited by Klarre; Mar 3rd, 2008 at 2:58 PM.

Mar 3rd, 2008, 3:21 PM	#2
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 297 Rep Power: 4	Re: [MASM32] Working with arrays After finding the "Memory" debug window in Visual Studio, it was pretty simply to solve the bug. The functions is now looking like this and seems to work fine. (Toggle Plain Text) ; ------------------------------------------------------------------------------ input_create proc invoke crt_malloc, 256 ; Allocate 256 Bytes for the key array mov g_keys, eax ; Store the key array pointer invoke crt_memset, g_keys, 0, 256 ; Make sure no buttons are pressed ret input_create endp ; ------------------------------------------------------------------------------ input_is_key_pressed proc key:dword mov eax, g_keys ; Get the key array address add eax, key ; Offset to the correct position in the array mov ah, [eax] ; Read the value on the position in the array .if(ah) mov eax, 1 .else mov eax, 0 .endif ret input_is_key_pressed endp ; ------------------------------------------------------------------------------ input_create proc invoke crt_malloc, 256 ; Allocate 256 Bytes for the key array mov g_keys, eax ; Store the key array pointer invoke crt_memset, g_keys, 0, 256 ; Make sure no buttons are pressed ret input_create endp ; ------------------------------------------------------------------------------ input_is_key_pressed proc key:dword mov eax, g_keys ; Get the key array address add eax, key ; Offset to the correct position in the array mov ah, [eax] ; Read the value on the position in the array .if(ah) mov eax, 1 .else mov eax, 0 .endif ret input_is_key_pressed endp __________________ http://www.klarre.se

Mar 9th, 2008, 7:24 AM	#3
Irwin Newbie Join Date: Mar 2008 Posts: 9 Rep Power: 0	Re: [MASM32] Working with arrays (Toggle Plain Text) IsKeyPressed proc Key:DWORD mov ecx, [dwKey] movzx eax, byte [gKeys+ecx] test eax, eax sete al ret IsKeyPressed endp InputCreate proc push 256d push GPTR ; memory is filled with 0's call GlobalAlloc push 27d push IsKeyPressed ret InputCreate endp IsKeyPressed proc Key:DWORD mov ecx, [dwKey] movzx eax, byte [gKeys+ecx] test eax, eax sete al ret IsKeyPressed endp InputCreate proc push 256d push GPTR ; memory is filled with 0's call GlobalAlloc push 27d push IsKeyPressed ret InputCreate endp Also, a word to the wise. Don't use MSVCRT in ASM, it completely destroys the purpose of using ASM. The converting is fairly easy too: malloc -> GlobalAlloc memset -> stosb/stosw/stosd/stosq

Mar 9th, 2008, 1:55 PM	#4
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 297 Rep Power: 4	Re: [MASM32] Working with arrays Thanks for your input Irwin. I removed the msvcrt dependency from my project and changed the malloc function call to HeapAlloc since I read on MSDN that GlobalAlloc wasn't recommended. Another question you may be able to answear on: Is it possible to link a program using the Visual Studio linker without linking with msvcrt.lib? I have set the entry point to main, but still got two linker errors I can't get rid of. So I guess it is impossible, right? (Toggle Plain Text) Error 1 error LNK2001: unresolved external symbol __RTC_Shutdown main.obj Error 2 error LNK2001: unresolved external symbol __RTC_InitBase main.obj Error 1 error LNK2001: unresolved external symbol __RTC_Shutdown main.obj Error 2 error LNK2001: unresolved external symbol __RTC_InitBase main.obj __________________ http://www.klarre.se

Mar 10th, 2008, 5:02 AM	#6
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 297 Rep Power: 4	Re: [MASM32] Working with arrays Ah, I see. Going to read up a little bit about the alloc functions. I am using the /NODEFAULTLIB linker flag and have set the entry point. But this will not get rid of the linker errors... __________________ http://www.klarre.se

Mar 10th, 2008, 7:23 AM	#8
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 297 Rep Power: 4	Re: [MASM32] Working with arrays The source file: (Toggle Plain Text) int main() { return 0; } int main() { return 0; } The linker command line (debug configuration): (Toggle Plain Text) /OUT:"G:\workspace\linktest\linktest\Debug\linktest.exe" /INCREMENTAL /NOLOGO /MANIFEST /MANIFESTFILE:"Debug\linktest.exe.intermediate.manifest" /NODEFAULTLIB /SUBSYSTEM:CONSOLE /ENTRY:"main" /MACHINE:X86 /ERRORREPORT:PROMPT /OUT:"G:\workspace\linktest\linktest\Debug\linktest.exe" /INCREMENTAL /NOLOGO /MANIFEST /MANIFESTFILE:"Debug\linktest.exe.intermediate.manifest" /NODEFAULTLIB /SUBSYSTEM:CONSOLE /ENTRY:"main" /MACHINE:X86 /ERRORREPORT:PROMPT Causes these errors: (Toggle Plain Text) 1>Linking... 1>main.obj : error LNK2001: unresolved external symbol __RTC_Shutdown 1>main.obj : error LNK2001: unresolved external symbol __RTC_InitBase 1>G:\workspace\linktest\linktest\Debug\linktest.exe : fatal error LNK1120: 2 unresolved externals 1>Linking... 1>main.obj : error LNK2001: unresolved external symbol __RTC_Shutdown 1>main.obj : error LNK2001: unresolved external symbol __RTC_InitBase 1>G:\workspace\linktest\linktest\Debug\linktest.exe : fatal error LNK1120: 2 unresolved externals The linker command line (release configuration): (Toggle Plain Text) /OUT:"G:\workspace\linktest\linktest\Release\linktest.exe" /INCREMENTAL:NO /NOLOGO /MANIFEST /MANIFESTFILE:"Release\linktest.exe.intermediate.manifest" /NODEFAULTLIB /SUBSYSTEM:CONSOLE /OPT:REF /OPT:ICF /LTCG /ENTRY:"main" /MACHINE:X86 /ERRORREPORT:PROMPT /OUT:"G:\workspace\linktest\linktest\Release\linktest.exe" /INCREMENTAL:NO /NOLOGO /MANIFEST /MANIFESTFILE:"Release\linktest.exe.intermediate.manifest" /NODEFAULTLIB /SUBSYSTEM:CONSOLE /OPT:REF /OPT:ICF /LTCG /ENTRY:"main" /MACHINE:X86 /ERRORREPORT:PROMPT Causes these errors: (Toggle Plain Text) 1>Linking... 1>main.obj : error LNK2001: unresolved external symbol @__security_check_cookie@4 1>G:\workspace\linktest\linktest\Release\linktest.exe : fatal error LNK1120: 1 unresolved externals 1>Linking... 1>main.obj : error LNK2001: unresolved external symbol @__security_check_cookie@4 1>G:\workspace\linktest\linktest\Release\linktest.exe : fatal error LNK1120: 1 unresolved externals __________________ http://www.klarre.se

Mar 10th, 2008, 10:40 AM	#9
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 297 Rep Power: 4	Re: [MASM32] Working with arrays Oh, I meant in a C++ project, which I forgot to mention in the earlier posts. __________________ http://www.klarre.se

Mar 10th, 2008, 10:41 AM	#10
Irwin Newbie Join Date: Mar 2008 Posts: 9 Rep Power: 0	Re: [MASM32] Working with arrays Oh, the problems aren't in your linking flags but rather your compiler flags. Just add /GS- to your compiler flags. Good luck Also, it's fine; I also code in C(++)

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Programming Forums > Application Development > Assembly

[MASM32] Working with arrays