[SDL] Extending SDLActivity (2.0.1/Android)

Gabriele Greco gabriele.greco at darts.it
Thu Oct 24 06:36:32 PDT 2013

Thanks Joseph, that was quite helpful. There was a lot of jargon in there that I've seen before, but wasn't sure how it all came together until now.

So that reminded me of another, similar question that I was planning to ask:

What is the best way to organize a C project for distributing to multiple platforms? I'm planning on building a command-line tool with C that uses SDL that will be distributed to lots of different OSes. I'd rather not require that SDL already be installed, but find a way to distribute it with my program. It would be even better if my users didn't have to compile anything because it was "precompiled". How can I simplify the installation process for my users and account for the variations in platforms?


Andrew Havens

On October 16, 2013 at 3:44:08 PM, T. Joseph Carter (tjcarter at spiritsubstance.com) wrote:

First the easy answer: Lots of libraries began shipping themselves  
with *-config programs. They all took basically the same args,  
--cflags and --libs. They were so similar and so common that someone  
got a brilliant idea: let's produce ONE program, call it pkg-config,  
that does it in a common, standard way.

So they're basically the same thing. If you use pkg-config, it  
becomes absolutely trivial to write a configure test for a library.


The limitations of make

CMake isn't necessarily better than make for what make does. Well,  
except that telling make about your source code's header dependencies  
in an automatic fashion is not as trivial as we'd like.

It is better than make for what it does NOT do, however. If you look  
at a pristine SDL source tree, it contains no makefiles. The reason  
is that it doesn't know what to build, what features to include, etc.

CMake and premake exist to solve that problem. :) The alternative  
are autoconf/automake/etc., and these are considered standard tools.

Why autotools suck

(Sorry in advance for the novel…)

The standard way to get those on UNIXy systems involves running a  
shell script, ./configure, which generates the makefiles using a  
macro language called m4. Basically imagine if C/C++ preprocessor  
directives like #include and #ifdef were a full scripting language  
unto themselves for generating C/C++ source. Yikes. :)

But you can't just write a configure script, because it too must be  
generated using m4 and other things by running a program called  
autoconf. And all of that is assuming you're just writing a simple  
program. If you're writing a library, or you want to avoid writing  
messy Makefile's, you use another layer on top of that called  
automake. Same deal, only it kind of generates input for autoconf.

Of course all of these may pull in dependencies on UNIX programs like  
sed, awk, and sometimes a whole scripting programming infrastructure  
called perl. In fact, if you want to build a dynamic library in an  
intelligent fashion, you're kind of best off using another add-on  
called libtool. Whether or not libtool constitutes doing something  
in an intelligent fashion is a matter of some debate, but what's not  
up for debate is that it DOES bring in a dependency on perl.

You may also have a dependency on stuff like pkg-config, which isn't  
really a classic UNIX "standard", but it makes configure test writing  
so easy that it's very common. And often, then you go and write the  
fallback if pkg-config is NOT installed. But not always.

And if all systems were UNIX, the dependencies aren't a big deal  
because… well, you've got them. But Bourne shell is a language, m4  
is a language, perl is a language, awk is a language, and sed is kind  
of almost a language. ;) (Basically, it's mini like a mini subset  
of vi's predecessor, ed. Think MS-DOS EDLIN, but for working with  

You've got to know about three languages, in addition to the one  
you're writing your code with, in order to compile it. And if there  
is a bug in your build system, you might need to know all of them!

It's also not conducive to using an IDE. Any IDE. If you're using  
that stinking heap of legacy crap left over from the 1970s, your  
development environment is the UNIX shell. Even if you use an IDE  
that cleverly tries to generate automake-compatible stuff in the  
background, I promise you, you WILL be using the command line to sort  
out your projects sooner or later.

Why CMake is better but not perfect

ONE language. The CMake interpreter has most of the features needed  
to reproduce all of the above autotools stuff built-in. It can build  
static libraries, shared libraries, packages, and even Mac frameworks  
and app bundles. Languages and compilers are just structures  
defining variables and a few test to find the appropriate compilers  
and whatnot for using that language on your system.

It has the same sort of include path setup autoconf/automake use, to  
find cmake macros/plugins, but these are all written in cmake's  
single language.

You're not forced to break up your project's build files all over the  
tree. You can make your build as modular as you want, or not, as you  
choose. While it's technically possible to do that with make, it's  
considered doing it wrong. :) There is no recursive make, nor is  
there need for it.

And dependencies? You've got one: CMake itself. That, your  
compiler, and your linker are all you need. Plus, CMake CAN generate  
make, MSVC, and XCode project files if you want it to. No IDE does  
(nor likely realistically could) read and write CMakeLists.txt (the  
CMake equivalent of a Makefile, ./configure, and everything), but an  
IDE could at least read that file and figure out what was part of  
your project easily enough.

Other alternatives

There's a few. SCons, premake, others… But it's kind of like  
alternatives for Subversion and CVS: There are many, but git has kind  
of risen to the top. Almost to the point that CVS and Subversion are  
considered inferior alternatives to git, whereas Mercurial would be  
considered fairly comparable.

CMake hasn't reached that level of prominence. Autotools are still  
the standard, even if CMake is simply a better choice. But there  
isn't a perfect solution out there that meets everyone's needs. When  
there is, there will be much rejoicing. :)


On Tue, Oct 15, 2013 at 10:03:58PM -0700, Andrew Havens wrote:
>Yeah, I'm not interested in using XCode either. I'd rather not depend on an IDE. I've got a Makefile for automating the compile task. I've seen other projects use cmake, but I'm not familiar with what makes it different/better than make.
>The pkg-config and sdl-config look awfully similar…what's the difference? Why would I want to use sdl-config instead?

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