Hi there,

I am using Allegro for quite a while now.
Recently I stumbled across something I wanted to try out for a long time, DLL files.
So, after trying out a little bit, I wanted to implement Allegro functions in a DLL file.
I know it probably sounds way too far fetched and inefficient, but I'm just doing this to learn a bit more.
So, my problem is as follows.
I created a DLL file (all the settings in my compiler, MSVC++, are set correctly, so no problems there).
I could compile that DLL file without any problems at first, but after including the header file "allegro_native_dialog.h", things went south.
I got the following error messages and warning:

Warning 1 warning LNK4086: entrypoint '_mainCRTStartup' is not __stdcall with 12 bytes of arguments; image may not run C:\Users\Remco\Documents\Visual Studio 2010\Projects\Project_SandBox_Engine\Debug\Project_SandBox_Engine.dll 1 1 Project_SandBox_Engine

Error 2 error LNK2019: unresolved external symbol _main referenced in function ___tmainCRTStartup C:\Users\Remco\Documents\Visual Studio 2010\Projects\Project_SandBox_Engine\Project_SandBox_Engine\MSVCRTD.lib(crtexe.obj) Project_SandBox_Engine

Error 3 error LNK1120: 1 unresolved externals C:\Users\Remco\Documents\Visual Studio 2010\Projects\Project_SandBox_Engine\Debug\Project_SandBox_Engine.dll 1 1 Project_SandBox_Engine

Now, without including that specific header, everything works fine, except for the fact that I cannot use the desired function "al_show_native_message_box(...)", which I'd like to implement inside my DLL.

Here's my code for the DLL project:

Header file:

CPP file:

The project is set as a Dynamic Library (.dll), and I have a global definition set for "COMPILE_ENGINE".

Once again, I know that what I'm trying to to is quite inefficient, but I'd still love to see this work, and I hope to achieve that with your help!

Greetings,
RemmyDZ

Thanks for your quick reply!

Well, the reason I thought it'd be inefficient is that Allegro already works with a DLL itself, the monolith-thingy.
So my initial thought was that using that DLL inside another DLL would be quite useless, nevertheless I wanted to try it out.
So it actually is efficient?
Is that because you can reuse the created DLL for other projects for instance?

Anyways, I'll try out your suggestion and see if it works, thanks!

EDIT:

Allright, I tried using the mt-debug, but it still gave me the same errors and warning.
After trying a few things, I noticed two things.
First, it compiles just fine with only the "allegro.h" header included, but it starts giving errors when including the "allegro_native_dialog.h" header.
Now, I also noticed that, when searching online for my error message, people who are experiencing this error all forgot to write a main function in their CPP file.
I know that a DLL file doesn't need a main function, and maybe it even doesn't function with one (no idea on that one), but, when addind the following code to my CPP file, it compiles just fine:

Will my DLL still work this way, or is there another solution without having to include a main function in my project?

Greetings,
RemmyDZ

Can you try using the separate allegro DLLs instead of monolith? Something like this (I don't really know the exact names):

#pragma comment(lib, "allegro-5.0.10-md-debug.lib")
#pragma comment(lib, "allegro-5.0.10-native_dialog-md-debug.lib")
#pragma comment(lib, "allegro-5.0.10-main-md-debug.lib")

By "toolchain" I meant the chain of tools used to build the program. Typically there's a C pre-processor, a compiler, and a linker. In Visual Studio, this is all hidden away from you, and instead you would configure them all using Visual Studio's project settings, and that would pass the appropriate options onto the command line tools.

There isn't going to be a main function in Allegro. There shouldn't be. There's only supposed to be one main function ([C++:] at least with any given signature) and that's typically going to be defined by the program author, not the library author. However, there's no reason that your DLL should require a main function...

It sounds like there's an "entry point" function that is supposed to be optional. This says that the run-time might provide one for you to use. If not, I don't know, maybe you should define an empty one? But I don't think it needs to be called main (and I'd assume it shouldn't since it serves a different purpose).

I don't know. Maybe look into that and see if it sheds any light on things.

Once again thanks for the replies!

I actually found out that I didn't do my research well enough.
It turns out that I get the same errors and warning when I compile with just the "allegro.h" header file included.
What I basically did was including that header file and not using any Allegro functions throughout the code.
So, just including any of those Allegro header files gives me those errors.
Including the "allegro_image.h" header file makes it even weirder:

I tried the DllMain function as suggested, but to no avail.

Inside my MSVC options I tried compiling with both /NOENTRY and without, but as long as there are Allegro header files involved, I'm not getting anything compiled.

EDIT:
Nevermind, when having both "allegro.h" and "allegro_image.h" included, I don't get the errors stated above, but I still keep the 2 errors and 1 warning from earlier.

EDIT #2:

It seems like my problem is solved!
I don't want to jump on the hype train too soon, but my DLL compiles fine so far!
As happy as I am, I'll be going to bed right now, so I haven't tested if the DLL actually works, but here's what I did:

I kept searching on internet for my error, and once I also used the word "Allegro" in my search keys, I came across this post:

So, I added the following code to my CPP file:

And voila, it worked!
I'll post the results tomorrow, as I'm about to sleep right now.

Cheers!
RemmyDZ