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diff --git a/doc/crosscompile.html b/doc/crosscompile.html new file mode 100644 index 0000000..ba22b31 --- /dev/null +++ b/doc/crosscompile.html @@ -0,0 +1,93 @@ +<html> + <head> + <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> + <meta http-equiv="Content-Language" content="en" /> + <title>How to cross-compile skalibs</title> + <meta name="Description" content="How to cross-compile skalibs" /> + <meta name="Keywords" content="skalibs build cross-compilation" /> + <!-- <link rel="stylesheet" type="text/css" href="http://skarnet.org/default.css" /> --> + </head> +<body> + +<p> +<a href="index.html">skalibs</a><br /> +<a href="http://skarnet.org/software/">Software</a><br /> +<a href="http://skarnet.org/">skarnet.org</a> +</p> + +<h1> How to cross-compile skalibs </h1> + +<p> + There are three issues in the world of cross-compilation: +</p> + +<ul> + <li> support for parallel builds: the source directory must be read-only +and each build process must have its own build tree. </li> + <li> support for compiler options: to specify the target architecture, +the header and library files that should be used, etc. + <li> build-time tests performed on the build architecture are invalid +if the target architecture is different. </li> +</ul> + +<h2> Support for parallel builds </h2> + +<p> + skalibs does not support out-of-tree builds at the moment, +but since the source code tree is small, it's not costly to duplicate it +to perform parallel builds. If the source code trees grows significantly +larger, out-of-tree build support will be considered. +</p> + +<h2> Support for build-time options </h2> + +<p> + skalibs now uses a standard <tt>./configure && make && make install</tt> +process, and cross-compiling build-time options can be given on the +<tt>./configure</tt> command line. +</p> + +<h2> Bypassing the build-time tests </h2> + +<p> + This is the hardest part of cross-compilation, and very few build systems +get it right. (GNU autotools does not, which is one of the reasons why +skarnet.org packages do not use autotools.) +</p> + +<p> + Native build procedures usually perform build-time tests: they compile +executables and run them (on the build platform, which is the same as +the target platform) to check for features and system quirks. skalibs +does exactly that: the <tt>./configure</tt> step performs tests on the +build platform and stores the system-dependent results in a directory +that it calls the <em>sysdeps</em> for this platform. +</p> + +<p> +But in a +cross-compilation environment, build-time tests are invalid, since the build +platform and the target platform differ. + There is only one way to cross-compile portable code without resorting +to build-time autodetection: +<strong>you must provide by hand the sysdeps for your target +architecture</strong>, via the --with-sysdeps option to configure. +</p> + +<p> + The easiest way to get the correct sysdeps for a target achitecture is +to natively compile skalibs on that target, and steal the produced sysdeps +files. It can be easily done with a virtual machine, qemu for instance. +You could also (politely) ask for precompiled sysdeps on the +skaware mailing-list, if you cannot find them anywhere on the Internet. +</p> + +<h2> Credits </h2> + +<p> +<a href="http://www.kegel.com/">Dan Kegel</a> brought up the need for a +clean cross-compilation system. +</p> + +</body> +</html> |