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Cross-Porting Software: Difference between revisions
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You extract the source code somewhere appropriate:
<
# Use --extract --file if you have a hard time surviving xkcd 1168.
tar -xf libfoo-4.2.tar.xz
</syntaxhighlight>
== pkg-config ==
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Libraries increasingly provide pkg-config files that describe where the headers are installed and how to link against the library (and private library dependencies if statically linked). Working with pkg-config is preferable to fighting it (see below on packages rolling their own foo-config program) and it nicely supports system roots and is cross-compile aware. It's possible to compile a custom cross-pkg-config, or you can simply wrap your system one. Make a <tt>x86_64-myos-pkg-config</tt> executable shell script and put it somewhere in your path for the duration of the cross-compilation:
<
#!/bin/sh
# Fill these in appropriately:
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# record that only static libraries were built.
exec pkg-config --static "$@"
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You then set <tt>PKG_CONFIG=x86_64-myos-pkg-config</tt> to packages use your custom pkg-config instead, and <tt>PKG_CONFIG_FOR_BUILD=pkg-config</tt> so packages that wish to compile local programs use the system pkg-config.
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Secondly, you cross-build the package in this manner:
<
# Potentially unset CC and such here (see configure --help) to prevent local
# tools from being mistakenly used as cross-tools. Alternatively, set them to
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make
make DESTDIR=$SYSROOT install
</syntaxhighlight>
This will cross-compile the software and install it under <tt>/usr</tt> on your system, inside your system root as the temporary installation location. Note how many packages remember <tt>--prefix</tt> and use it at runtime to locate their data files. You must not do <tt>--prefix=$SYSROOT/usr</tt> as that means libfoo would look files in <tt>/home/myuser/myos/sysroot/usr/share/libfoo</tt> while running on your operating system instead of <tt>/usr/share/libfoo</tt>. The <tt>DESTDIR</tt> acts as a second prefix for the purpose of installation, it's not revealed to the package before the install step, so it won't mistakenly remember it.
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