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@@ -1 +1,106 @@ -slibtool: a skinny libtool implementation, written in C +# slibtool + +`slibtool` is an independent reimplementation of the commonly used libtool, +written in C. `slibtool` is designed to be a clean, fast, easy-to-use +libtool drop-in replacement, and is accordingly aimed at package authors, +distro developers, and system integrators. `slibtool` maintains compatibility +with libtool in nearly every aspect of the tool's functionality as well as +semantics, leaving out (or turning into no-ops) only a small number of +features that are no longer needed on modern systems. + +Being a compiled binary, and although not primarily written for the sake of +performance, building a package with `slibtool` is often faster than with its +script-based counterpart. The resulting performance gain would normally vary +between packages, and is most noticeable in builds that invoke libtool a large +number of times, and which are characterized by the short compilation time of +individual translation units. + +## Requirements for building slibtool + +- a C toolchain, consisting of... + - a C compiler such as gcc, clang, or [cparser]. + - The compiler should support -std=c99. + - The system's libc should support -D_XOPEN_SOURCE=700. + +## Usage + +With most packages, simply adding `LIBTOOL=slibtool` to the `make` invocation +should suffice. To have `slibtool` operate in debug mode (outputting a colorized +raw argument vector), use `LIBTOOL=dlibtool` instead, or alternatively add +`--debug` to the libtool flags inside of your Makefile. + +### Corner cases + +Some programs which make heavy use of recursive `make` are known to drop the +`LIBTOOL` value at some point in the process, and as such you may additionally +need to export the environment variable; `export MAKE="make LIBTOOL=slibtool"`. + +`slibtool` additionally installs two symlinks that are the equivalent of +`-disable-shared` and `-disable-static`, named `slibtool-static` and +`slibtool-shared`, respectively. These symlinks should be used when building +packages that have the above switches hard-coded into the generated libtool +script; two examples of such packages are `binutils` and `gdb`, which both have +shared library builds disabled by default. A quick way to determine whether this +invocation form is appropriate is to run `./libtool --features` from the build +directory, then check whether the output has either shared or static library +builds disabled. + +## Differences from GNU libtool + +While `slibtool` aims to be compatible with all common usages of libtool, there +are a few differences at the implementation level that should be noted. + +- `-rpath` argument values are passed to the compiler and linker as needed only; + `-rpath` is often [mis]used by libtool to add redundant paths to a program's + linker search path. When using slibtool, `-rpath` argument values are only + forwarded to the compiler and linker when pointing to non-default linker + directories, and are accordingly filtered out when pointing to default library + locations (i.e. `/usr/lib`, `/lib`, and so on). + +- no-ops + - `-R`, which adds a path to the generated program's run-time search path; + this switch is currently not needed, and is accordingly ignored. + - `-export-symbols`, which exports symbols listed in a given file, and + `-export-symbols-regex`, which exports symbols matching a regex; + both are unimplemented because similar functionality has long been + provided by the compiler or toolchain; `gcc` has supported setting ELF + visibility since v4.0, for instance, and PE import library support is + provided by slibtool via the --output-def linker switch and a subsequent + invocation of dlltool. + - `-no-install`, which considers the executable wrapper to be optional; + this switch is not needed on modern systems, and is accordingly ignored. + +- No `libltdl`. + libltdl is nowadays no longer needed; it serves to provide a `dlopen()` + functionality on systems which do not offer it, i.e. HP-UX and BeOS, + however since neither HP-UX nor BeOS is currently supported by slibtool, + there exists no urgent need to provide equivalent functionality. + +## Development + +Major changes to slibtool should be discussed on [#midipix] prior to pursuing +a considerable effort, and patches should be sent, gpg-signed, to the project +maintainer; before hacking on slibtool, please take a moment of your time and +read the [CONTRIB] document. + +Before finalizing your changes, please consider building at least once with +`cparser` as the compiler. cparser is excellent at catching logical errors +and semantic flaws, and at the time of this writing is capable of spotting +some errors that go unnoticed by the other major open source compilers. +For a few examples of such errors, see commits [94d109f], [1142bf2], and +[55c95a8]. + +## License + +`slibtool` is distributed under a permissive [MIT license]. + +[MIT license]: http://git.midipix.org/cgit.cgi/slibtool/tree/COPYING.SLIBTOOL +[libltdl]: https://www.gnu.org/software/libtool/manual/html_node/Using-libltdl.html#Using-libltdl +[dlopen()]: http://pubs.opengroup.org/onlinepubs/9699919799/functions/dlopen.html +[CONTRIB]: http://git.midipix.org/cgit.cgi/slibtool/tree/CONTRIB +[libtool]: https://www.gnu.org/software/libtool/ +[#midipix]: irc://irc.freenode.net/#midipix +[cparser]: http://pp.ipd.kit.edu/git/cparser/ +[94d109f]: http://git.midipix.org/cgit.cgi/slibtool/commit/?id=94d109fa418c024c214a50d645624e2e2935e6d1 +[1142bf2]: http://git.midipix.org/cgit.cgi/slibtool/commit/?id=1142bf2e13f411cf967c1ed8b4060d7829eb13bb +[55c95a8]: http://git.midipix.org/cgit.cgi/slibtool/commit/?id=55c95a829928ae9f053678a58a2145276cad9c08 |