Re: [Nasm-users] How to call MessageBoxA from Nasm program?

[Ermin R. A. <e.a...@st...>]

If I recall correctly, whenever I tried to use Win32 in my asm code I had to:
a) use extern _MessageBoxA@16 (or whatever function I used)
b) add User32.lib (or appropriate import library) to the linker
Check up on stdcall name decorating if you're wondering why MessageBoxA is like that.

Hope that helps,
Robert

-----Original Message-----
From: <oh...@co...>
To: Frank Kotler <fbk...@zy...>
Date: Thu, 7 May 2009 5:52:23 -0400
Subject: Re: [Nasm-users] How to call MessageBoxA from Nasm program?

Hi,

To answer your question:  I'm using the MS linker from Visual Studio 2008.

So, are you saying that I can eliminate both the "extern" and the "import"?

Thanks,
Jim



---- Frank Kotler <fbk...@zy...> wrote: 
> oh...@co... wrote:
> > Hi,
> > 
> > I'm trying to add a call to MessageBoxA in a Nasm app.  I know how to setup the parameters for the call, but I can't get Nasm to assemble successfully.
> > 
> > I have added an "extern MessageBoxA" and "import MessageBoxA user32.dll" (this is on Windows), but when I do that, I get an error from parser saying that an instruction is expected.
> > 
> > If I comment out the "import" line, I get a linker error.
> > 
> > Am I not suppose to use both the "extern" and "import" lines, before the .Code line?
> 
> Mmmm, yes, but only in "-f obj" output format (which defaults to 16-bit 
> and requires some "cruft" to tell Nasm we want 32-bit). Supposedly, in 
> "-f win32" format, we "don't need" it. I think the reason we "don't 
> need" it is that we are expected to link with an "import library" on the 
> linker command line. I am told that we can create our own import library 
> by assembling "extern MessageBoxA" and "import MessageBoxA user32.dll" 
> (with other extern/imports we need, presumably) as "-f obj" and linking 
> the produced .obj with the .obj containing your code (assembled as "-f 
> win32") - despite the different linkable object formats, this is 
> supposed to work. I was told this after I'd quit running Windows, so 
> never had a chance to try it. I think the more "usual" way would be to 
> link against an import library supplied with your linker(?). This raises 
> the obvious question: which linker are you using? And what, if anything, 
> came with it? I don't know much about Windows linkers - I used Alink, 
> mostly, for the few Windows programs I tried. I think Golink and Polink 
> are more common these days.
> 
> You might want to download the "nasmx" package:
> 
> http://www.asmcommunity.net/projects/nasmx/
> 
> Recent versions have been in .exe format, so I can't even look at it to 
> see what's there. Uses Golink, it says that on the web page... If it 
> doesn't include a "win32.lib" or such, the examples may give you an idea 
> how to function without it.
> 
> If all else fails...
> 
> http://home.comcast.net/~fbkotler/win32nasmbase.zip
> 
> ...as I recall, that includes a library that worked with "-f win32", 
> although it is extremely old and obsolete...
> 
> This question about "import" comes up fairly often, and I don't really 
> have a "good" answer to it, besides "it's for -f obj only" and we "don't 
> need" it for -f win32... Anyone got a clearer idea on this?
> 
> Best,
> Frank
> 
> 


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Robert Alegrid
#3164658
BP-079 Bachelor of Science (Physics)
BP-083  Bachelor of Applied Science (Mathematics)