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iphonegccmakefilecross-compilingconfigure
ggambetta
ggambetta

Reputation: 3443

Cross-compiling Makefile: dealing with test programs

I'm trying to cross-compile several libraries from OSX to iOS. I've successfully cross-compiled libjpeg and libogg.

But I can't compile libvorbis because configure insists on creating and running a small test program. This obviously fails, because it creates an armv7 binary, fails to run it, and then interprets this as missing ogg libraries.

How do you usually deal with this kind of problem? I'm tempted to hack the configure script to work around these issues, but because of this kind of failure some features may be disabled. I'm also thinking of letting configure generate a native Makefile and then convert it to use the iOS toolchain, but this seems too error prone.

Any advice?

Upvotes: 2

Views: 1897

Answers (2)

ggambetta
ggambetta

Reputation: 3443

I finally figured it out. I tricked configure by explicitly making it link with ogg (LDFLAGS="/usr/local/ios/lib/libogg-armv7.a" ./configure ...) and then removed the explicit reference to the library from the generated makefile.

Upvotes: 1

kanaka
kanaka

Reputation: 73197

If you are cross-compiling anything that has more dependencies than libc (glibc) it becomes much more complicated. You need to have already cross-compiled all the dependencies. And the cross-compiler toolchain and all helper build programs and scripts need to know how to find those dependencies (the cross-compiled libraries and headers).

You need to have already cross-compiled libogg (and its dependencies) and installed them into the cross-compile root directory. The headers and libraries from your build system can't be used for the host (arm7) system. They must be kept separate.

Also, if you want to have shared object libraries (*.so) and not just static libraries then there is a whole new set of complications. For example, while a cross-compiler toolchain contains a cross-compiled libc as part of the toolchain, you still need a libc for the host system. The libc that is part of the toolchain can be used for this, but the way it is structured is different than on the host system. Sometimes people copy and re-arrange the files, but often people just compile and install a new glibc for the root.

Anyways, all that to say, the two errors you are seeing are because the configure script is not able to find a cross-compiled libogg library. If you haven't already, you need to cross-compile libogg (and dependencies) and install them into your target root. Then you need to tell the configure script where your cross-compiled headers (yes, header are architecture specific) and libraries are in your target root. Usually using CFLAGS, LDFLAGS, CXXFLAGS, etc (NOT --prefix) but there may be other environment variables you need to set also to affect things like pkg-config, etc. After you have built each dependency, then you need to get the makefile to install the dependency to the root. Usually this is done with make DESTDIR=[root] install but some makefiles have their own mechanism (or no proper alternate install mechanism).

You may also need to override certain configure checks (using environment variables) that are poorly written and don't have good cross-compile defaults. These variables usually start with ac_cv_*

So the basic process is to do this for packages that you need (in dependency order):

export CFLAGS=-I[root]/usr/include LDFLAGS=-L[root]/usr/lib CXXFLAGS=-I[root]/usr/include
export ac_cv_[test1]=[yes|no] ac_cv_[test2]=[yes|no] ...
./configure --host=[arm7-blah-blah]
make
make DESTDIR=[root] install

Good luck. Once you feel comfortable with standard cross-compiling, then you will be ready to take on the real black art, the Canadian cross ;-)

Upvotes: 3

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