Build Instructions ------------------ * Requirements ------------ - A POSIX-compliant C development environment - GNU make version 3.81 or later - If cross-compiling: the sysdeps for your target architecture (see the "Cross-compilation" section below) This software will install on any operating system that implements POSIX.1-2008, available at: http://pubs.opengroup.org/onlinepubs/9699919799/ * Standard usage -------------- ./configure && make && sudo make install will work for most users. It will install the static libraries in /usr/lib/skalibs, the shared libraries in /lib, and the sysdeps in /usr/lib/skalibs/sysdeps. You can strip the libraries of their extra symbols via "make strip" before the "make install" phase. It will shave a few bytes off them. * Customization ------------- You can customize the installation process via flags given to configure. See ./configure --help for a list of all available configure options. * Environment variables --------------------- Controlling a build process via environment variables is a big and dangerous hammer. You should try and pass flags to configure instead; nevertheless, the standard environment variables are recognized. The value of the CROSS_COMPILE environment variable will prefix the building tools' names. The --enable-cross option is preferred, see "Cross-compilation" below. If the CC environment variable is set, its value will override compiler detection by configure. The values of CFLAGS, CPPFLAGS and LDFLAGS will be appended to flags auto-detected by configure. To entirely override the flags set by configure instead, use make -e. The Makefile supports the DESTDIR convention for staging. * Shared libraries ---------------- Software from skarnet.org is small enough that shared libraries are generally not worth using. Static linking is simpler and incurs less runtime overhead and less points of failure: but since skalibs only provides libraries, both versions are built by default. Nevertheless, you can: * avoid building shared libraries: --disable-shared * avoid building static libraries: --disable-static If you are using a GNU/Linux system, be aware that the GNU libc behaves badly with static linking and produces huge executables, so if you plan on making static executables, you should consider using another libc, which you also need to use when compiling skalibs. musl is recommended: http://musl-libc.org/ * Cross-compilation ----------------- skarnet.org centralizes all the difficulty of cross-compilation in skalibs. The native skalibs build process runs some tests to gather "sysdeps", i.e. system-dependent properties of the target, and stores those into a sysdeps directory; software depending on skalibs is provided the name of the sysdeps directory at build time, and can depend on its contents - that's how skarnet.org packages are easily made portable. However, when the host differs from the target - the cross-compilation case - those build-time tests are invalid. So you must provide configure with a precomputed sysdeps directory, containing valid sysdeps values for your target. Use the --with-sysdeps=DIR option to specify DIR as a sysdeps directory for your target. Also use the --enable-cross=PREFIX option to specify a cross-compiling PREFIX for your toolchain's binaries, or simply --enable-cross if your default toolchain is a cross-compiler. If you know the peculiarities of your target system, you can build a sysdeps directory by hand. However, a much easier, and recommended, method of obtaining sysdeps, is to natively determine them (via ./configure) in a virtual machine, for instance provided by qemu. If you are using Linux, simple root filesystems bootable with qemu for testing purposes are available at Aboriginal Linux: http://landley.net/aboriginal/ Precomputed sysdeps for various targets may also be available on skarnet.org or on third-party sites. Once you have gathered your sysdeps, for any skarnet.org package: * give the correct --with-sysdeps option to ./configure * give the correct --enable-cross option * for --prefix, --bindir and other paths, always use the run-time path * to install the cross-compiled package in a staging directory /your/stage, perform "make install DESTDIR=/your/stage/" * The slashpackage convention --------------------------- The slashpackage convention (http://cr.yp.to/slashpackage.html) is a package installation scheme that provides a few guarantees over other conventions such as the FHS, for instance fixed absolute pathnames. skarnet.org packages support it: use the --enable-slashpackage option to configure, or --enable-slashpackage=DIR for a prefixed DIR/package tree. This option will activate slashpackage support during the build and set slashpackage-compatible installation directories. If $version is the current skalibs version number: --bindir will be set to /package/prog/skalibs-$version/command --includedir will be set to /package/prog/skalibs-$version/include --libdir will be set to /package/prog/skalibs-$version/library --dynlibdir will be set to /package/prog/skalibs-$version/library.so --sysdepdir will be set to /package/prog/skalibs-$version/sysdeps Note that --datadir will be unchanged, because the data exported by skalibs, i.e. the leap second table, is system-wide. You should manually specify --datadir=... if you want to deviate from the default. --prefix is pretty much ignored when you use --enable-slashpackage: it will only impact --datadir. You should probably not use both --enable-slashpackage and --prefix. When using slashpackage, two additional Makefile targets are available after "make install": - "make -L update" changes the default version of the software to the freshly installed one. (This is useful when you have several installed versions of the same software, which slashpackage supports.) - "make -L global-links" adds links from DIR/command and DIR/library.so to the default version of the binaries and shared libraries. The "-L" option to make is necessary because targets are symbolic links, and the default make behaviour is to check the pointed file's timestamp and not the symlink's timestamp. * Out-of-tree builds ------------------ skarnet.org packages do not support out-of-tree builds. They are small, so it does not cost much to duplicate the entire source tree if parallel builds are needed.