Re: [Qemu-devel] [PATCH] Fix SDL configuration for mingw32 cross compilation.

[Stefan Weil]

Anthony Liguori schrieb:
> Stefan Weil wrote:
>> When building QEMU for win32 on linux with mingw32,
>> configure must call ${cross_prefix}-sdl-config (not
>> sdl-config) to get the correct include and lib paths.
>>
>> The results of the native sdl-config are only valid
>> for native builds. They are useless for cross builds.
>>   
>
> No, when you cross compile sdl, you still end up with an sdl-config
> binary.  The solution is to install the binary to a different path and
> use PATH when building.
>
> Where did you get your cross build of SDL from?  I assume whoever
> packaged it renamed the binary but it's not what sdl actually does.
>

The PATH solution works (I used it, too), but it is bad:
you have to use a modified PATH for every cross build
(make calls configure when the configure script is updated).

http://www.libsdl.org/release/SDL-devel-1.2.9-mingw32.tar.gz
contains i386-mingw32msvc-sdl-config. It is rather old,
but I liked this and renamed it to i586-mingw32msvc-sdl-config.
When I installed newer versions of cross SDL, I made
a symbolic link from cross sdl-config to i586-mingw32msvc-sdl-config.

There is a quasi-standard for cross tools: binutils and gcc
are installed in a similar way. For example,
/usr/bin/i586-mingw32msvc-strip and
/usr/i586-mingw32msvc/bin/strip are (hard) linked.

If your cross sdl-config happens to be in
/usr/i586-mingw32msvc/bin and you add this to PATH,
you will see another problem caused by the PATH solution:
you will get the wrong binutils (ar, as, strip, ...)!
Ok, cross sdl-config (which is a script, not a binary)
can have its own directory, then this is not a problem.

sdl-config exists because users should not need to know
paths for includes, libs (and binaries) but have a simple
interface to ask for the information they need.

The same simple interface is needed for cross sdl.

There are no packages with cross build SDL (at least I
don't know any), so it is always a manual installation.
Adding a symbolic link is then easy:
ln -s /usr/i586-mingw32msvc/bin/sdl-config
/usr/bin/i586-mingw32msvc-sdl-config.
Looking for i586-mingw32msvc-sdl-config at google shows
that others use this solution, too.

Even better for most users would be a package or tar file
which installs the sdl cross environment needed for QEMU
mingw32 cross builds. Should I prepare one?

Or you could add a configure option which tells configure
where to look for sdl-config or its base directory,
something like --with-sdl-prefix=/usr/i586-mingw32msvc
(this is used by other projects, see google).

Regards

Stefan