Hello, I'm working on a program to set the forecolor and backcolor of some text. The program will debug but then crashes immediately. Because of this, it's giving me an access violation error. I'm using the Irvine.inc directory.
My code:
TITLE SetColor and WriteColorChar
SetColor PROTO forecolor:BYTE, backcolor:BYTE
WriteColorChar PROTO char:BYTE,forecolor:BYTE, backcolor:BYTE
.data
.code
main PROC
INVOKE WriteColorChar, 'A', white, blue
INVOKE WriteColorChar, 'B', blue, white
INVOKE WriteColorChar, 'C', green, black
INVOKE WriteColorChar, 'D', yellow, gray
INVOKE SetColor, lightGray, black
call Crlf
exit
main ENDP
WriteColorChar PROC, char:BYTE, forecolor:BYTE, backcolor:BYTE
pop ebp ; pop the ebp from the stack
pop ecx ; pop the ecx reg. from the stack
pop ebx ; pop the ebx reg. from the stack
pop eax ; pop the eax reg. from the stack
push eax ; push Foreground onto the stack
push ebx ; push background onto the stack
push ecx ; push wChar onto the stack
call SetColor ; call SetColor
call WriteChar ; call WriteChar
ret
WriteColorChar ENDP
SetColor PROC, forecolor:BYTE, backcolor:BYTE
push ebp ; Save calling procedure base pointer
mov ebp, esp ; Set base pointer for this procedure
mov ecx, [ebp + 16] ; Retrieve colors
mov eax, [ebp + 12] ; from the stack
mov ebx, 16 ; foreColor + (backColor * 16 )
mul ebx
add ecx, eax
mov eax, ecx ; move ecx reg. into eax re.
call SetTextColor ; call SetTextColor to set the fore and back colors
mov eax, [ ebp + 8 ] ; retreive the char from the stack
pop ebp ; Restore base pointer for calling procedure
ret
SetColor ENDP
END main
Any help would be greatly appreciated
You should reconsider your stack usage for both procedures. If you have any book, read up about calling conventions and the stack frame.
Thank you qWord. Does this have to do with my usage of ebp?
- Google for Masm Programmer's Guide
- Read Tips, Tricks & Traps (http://www.webalice.it/jj2006/Masm32_Tips_Tricks_and_Traps.htm)
- more specifically: the push ebp etc gets done automatically - check with Olly (http://www.ollydbg.de/version2.html). If you want to do it manually, you need to insert a specific instruction before the proc:
OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE
MyTest proc arg1, arg2
... your code ...
retn 2*DWORD
MyTest endp
OPTION PROLOGUE:PrologueDef
OPTION EPILOGUE:EpilogueDef
Note that you cannot use LOCAL with a manual stack frame, at least not so easily. And arguments should be DWORD (default), never BYTE. You cannot push a BYTE...
Last but not least: Welcome to the Forum :icon14:
there is also an issue to be aware of.....
the Irvine library has functions that are named "SetTextColor" and "GetTextColor"
these names conflict with windows API functions in the gdi32 dll
Thanks a lot for all the help! I found the MASM Programmers Guide and it has a lot of useful information. I'll need to crack down on that.
I've cleaned the code up a bit and seems to work ok but I'm a little confused because my assignment requires the use of BYTE parameters. The question is as follows:
SetColor receives two byte parameters: forecolor and backcolor. It
calls the SetTextColor procedure from the Irvine32 library. (2) WriteColorChar receives three
byte parameters: char, forecolor, and backcolor. It displays a single character, using the color
attributes specified in forecolor and backcolor. It calls the SetColor procedure, and it also calls
WriteChar from the kips library. Both SetColor and WriteColorChar must contain declared
parameters. Write a short test program that tests both procedures. Be sure to create PROTO declarations
for SetColor and WriteColorChar.
But you're stating I should never use BYTE?
Quote from: jj2007 on February 26, 2014, 04:51:39 AM- Google for Masm Programmer's Guide
- Read Tips, Tricks & Traps (http://www.webalice.it/jj2006/Masm32_Tips_Tricks_and_Traps.htm)
- more specifically: the push ebp etc gets done automatically - check with Olly (http://www.ollydbg.de/version2.html). If you want to do it manually, you need to insert a specific instruction before the proc:
OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE
MyTest proc arg1, arg2
... your code ...
retn 2*DWORD
MyTest endp
OPTION PROLOGUE:PrologueDef
OPTION EPILOGUE:EpilogueDef
Note that you cannot use LOCAL with a manual stack frame, at least not so easily. And arguments should be DWORD (default), never BYTE. You cannot push a BYTE...
Last but not least: Welcome to the Forum :icon14:
The problem with BYTE parameters is that there is bug in the INVOKE directive for MASM v6...8, which produce bad code. However, you can use later versions (9+) or jWasm that does not have this issue.
Thanks for the info. So after it was all said and done the program runs and shows the first "A" in white and blue like I want. However, the program then proceeds to crash before showing the rest of the letters. Any idea what could be causing this? I decided to use ebp because that's how the book explains it. Here's the updated code:
SetColor PROTO forecolor:DWORD, backcolor:DWORD
WriteColorChar PROTO char:DWORD,forecolor:DWORD, backcolor:DWORD
.data
.code
main PROC
INVOKE WriteColorChar, 'A', white, blue
INVOKE WriteColorChar, 'B', blue, white
INVOKE WriteColorChar, 'C', green, black
INVOKE WriteColorChar, 'D', yellow, gray
INVOKE SetColor, lightGray, black
call waitmsg
call Crlf
exit
main ENDP
OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE
WriteColorChar PROC, char:DWORD, forecolor:DWORD, backcolor:DWORD
pop ebp ; pop the ebp from the stack
pop ecx ; pop the ecx reg. from the stack
pop ebx ; pop the ebx reg. from the stack
pop eax ; pop the eax reg. from the stack
push eax ; push Foreground onto the stack
push ebx ; push background onto the stack
push ecx ; push wChar onto the stack
call SetColor ; call SetColor
call WriteChar ; call WriteChar
ret
WriteColorChar ENDP
OPTION PROLOGUE:PrologueDef
OPTION EPILOGUE:EpilogueDef
OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE
SetColor PROC, forecolor:DWORD, backcolor:DWORD
push ebp ; Save calling procedure base pointer
mov ebp, esp ; Set base pointer for this procedure
mov ecx, [ebp + 16] ; Retrieve colors
mov eax, [ebp + 12] ; from the stack
mov ebx, 16 ; foreColor + (backColor * 16 )
mul ebx
add ecx, eax
mov eax, ecx ; move ecx reg. into eax re.
call SetTextColor ; call SetTextColor to set the fore and back colors
mov eax, [ ebp + 8 ] ; retreive the char from the stack
pop ebp ; Restore base pointer for calling procedure
ret
SetColor ENDP
OPTION PROLOGUE:PrologueDef
OPTION EPILOGUE:EpilogueDef
END main
There are several issues here...
Inter alia, I would recommend that you use invoke instead of call. For example,
invoke SetTextColor would have choked with "error A2137: too few arguments to INVOKE" - and indeed, SetTextColor needs two DWORD arguments on the stack.
Please read the documentation for all the functions you are using. If your OS allows using *.hlp files, the Win32 help file is still available here (http://www.powerbasic.com/support/downloads/Microsoft%20Tools.htm).
Thank you for your response jj2007. I am using the SetTextColor from the Irvine Library and not from the Windows API. The example I referred to for my program was from here: http://programming.msjc.edu/asm/help/source/irvinelib/settextcolor.htm (http://programming.msjc.edu/asm/help/source/irvinelib/settextcolor.htm)as well as the book of course. I should have colors on the stack when using the following instructions right?
mov ecx, [ebp + 16]
mov eax, [ebp + 12]
I'm probably wrong because I'm receiving the access violation but I have not seen any errors about having too few arguments to INVOKE even when changing the call to Invoke.
no, no
SetTextColor from windows API (gdi32) requires 2 dword parameters on the stack
COLORREF SetTextColor(
_In_ HDC hdc,
_In_ COLORREF crColor
);
however, that function applies primarily to GUI apps
SetTextColor in the Irvine library has no stack parameters
; Receives: AX = attribute. Bits 0-3 are the foreground
; color, and bits 4-7 are the background color.
i have a modified version of kips library, in which i renamed this function to SetConTextColor
that avoids the name conflict
on another note.....
SetColor PROC, forecolor:DWORD, backcolor:DWORD
push ebp ; Save calling procedure base pointer
mov ebp, esp ; Set base pointer for this procedure
mov ecx, [ebp + 16] ; Retrieve colors
mov eax, [ebp + 12] ; from the stack
;
;
;
mov eax, [ ebp + 8 ] ; retreive the char from the stack[EBP] holds the preserved contents of EBP on the stack
[EBP+4] holds the RETurn address
[EBP+8] holds the forecolor
[EBP+12] holds the backcolor
there are cases where it's good to disable the prologue and epilogue
however, this doesn't appear to be one of them
it might be best to leave them enabled and let the assembler sort out the EBP offsets
Just wanted to thank everyone for their help as I got everything to work properly. I decided to not manually alter the stack as I'm obviously not experienced enough in that aspect.
Final code for those who care:
main PROC
INVOKE WriteColorChar, 'A', white, blue
INVOKE WriteColorChar, 'B', blue, white
INVOKE WriteColorChar, 'C', green, black
INVOKE WriteColorChar, 'D', yellow, gray
INVOKE SetColor, lightGray, black
call Crlf
call WaitMsg
exit
main ENDP
WriteColorChar PROC, char:dword, forecolor:dword, backcolor:dword
invoke SetColor, forecolor, backcolor
mov eax, char
invoke WriteChar
ret
WriteColorChar endp
SetColor PROC, forecolor:dword, backcolor:dword
mov eax, backcolor
shl eax, 4
add eax, forecolor
call SetTextColor
ret
SetColor ENDP