Letting <invoke MessageBox> display more than one string

[Rsir]

from Win32 API helpfile:

int MessageBox(

    HWND  hWnd,          // handle of owner window
    LPCTSTR  lpText,      // address of text in message box
    LPCTSTR  lpCaption,  // address of title of message box 
    UINT  uType            // style of message box
   );

MessageBox accepts one address for LPCTSTR lpText.
Does anyone know a trick to put more than one string in the window that is created by this function?
I already consulted the tuts of Iczelion, but didn't found anything usefull.

[ragdog]

Hi

Mean you this?

Code Select Expand


.data
szCaption db "Information",0
szText    db "Masm32",13,10
          db "------",13,10
          db "Masm32 example",0

.code

invoke MessageBox,NULL,addr szText,addr szCaption,MB_OK


[Rsir]

hi ragdog,
happy newyear.
No not quite.
More like this:

Code Select Expand

.data
szCaption db "Information",0
szText1   db "Masm32",0
szText2   db "------",0
szText3   db "Masm32 example",0

.code

invoke MessageBox,NULL,addr szText1+szText2+szText3,addr szCaption,MB_OK

I want to do a separate thing with szText2

[donkey]

Hi Rsir,

Obviously that is an unworkable solution since it is completely contrary to how data is passed to an API or even the fundamentals of how addresses work at any level, you will have to concatenate the strings then pass a single address to the function. Use lstrcat to combine the strings then pass the result...

Code Select Expand

buffer db 1024 DUP (?)

invoke lstrcpy, offset buffer, offset String1
invoke lstrcat, offset buffer, offset String2
invoke lstrcat, offset buffer, offset String3

invoke MessageBox,NULL,offset buffer,NULL,NULL

Although I am sure that there's a way to write a macro for this, most here know how I feel about macros ;)

[Rsir]

Thank you donkey.
I think your solution will work.
I realize that my 'pseudocode' looks funny, but you got the message.
Have a drink, prosit!

[Rsir]

Donkey,
Your code works fine.
To diminish the size of the exec the decl of the buffer can even be:

Code Select Expand

.data?
buffer  db ?
.code
thanks,
Rsir

[donkey]

Donkey,
Your code works fine.
To diminish the size of the exec the decl of the buffer can even be:

Code Select Expand

.data?
buffer  db ?
.code
thanks,
Rsir

Hi Rsir,

That's a recipe for disaster, setting the buffer length of a C string you will be building to a single byte guarantees a buffer over-run, perhaps in your tests you got lucky since Windows allocates space by pages and you didn't pass the page boundary however you can't guarantee that this will always be the case. Anyway, a 256 byte buffer of uninitialized data adds exactly the same amount of space to your executable as a 1 byte buffer or a 10 MB buffer, it's just an entry in a table and no physical space in the PE is allocated.

[Rsir]

-------------------------------------
sorry, you're right.
I made this mistake earlier and it then took me days to find out.