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diff --git a/INSTALL b/INSTALL index 9e2c0061..5b58693e 100644 --- a/INSTALL +++ b/INSTALL @@ -1,45 +1,58 @@ -A quick-and-simple guide to installing musl: +==== Installing musl ==== +musl may be installed either as an alternate C library alongside the +existing libraries on a system, or as the primary C library for a new +or existing musl-based system. -STEP 1: Configuration +First, some prerequisites: -Edit config.mak to override installation prefix, compiler options, -target architecture, etc. as needed. Currently supported archs are -i386 and x86_64. Otherwise, the defaults should be okay for trying out -musl with static linking only. +- A C99 compiler with gcc-style inline assembly support, support for + weak aliases, and support for building stand-alone assembly files. + gcc 3.x and 4.x are known to work. pcc and LLVM/clang may work but + are untested, and pcc is known to have some bugs. -DO NOT set the prefix to /, /usr, or even /usr/local unless you really -know what you're doing! You'll probably break your system such that -you'll no longer be able to compile and link programs against glibc! -This kind of setup should only be used if you're building a system -where musl is the default/primary/only libc. +- GNU make -The default prefix is /usr/local/musl for a reason, but some people -may prefer /opt/musl or $HOME/musl. +- Linux, preferably 2.6.22 or later. Older versions are known to have + serious bugs that will make some interfaces non-conformant, but if + you don't need threads or POSIX 2008 features, even 2.4 is probably + okay. -For shared library support, the dynamic linker pathname needs to be -hard-coded into every program you link to musl. Ideally, you should -leave the path ($syslibdir) set to /lib unless you are unable to -install files to /lib, in which case you can change it. +- A supported CPU architecture (currently i386, x86_64, or arm). +- If you want to use dynamic linking, it's recommended that you have + permissions to write to /lib and /etc. Otherwise your binaries will + have to use a nonstandard dynamic linker path. -STEP 2: Compiling -Run "make". (GNU make is required.) +== Option 1: Installing musl as an alternate C library == -STEP 3: Installation +In this setup, musl and any third-party libraries linked to musl will +reside under an alternate prefix such as /usr/local/musl or /opt/musl. +A wrapper script for gcc, called musl-gcc, can be used in place of gcc +to compile and link programs and libraries against musl. -With appropriate privileges, run "make install". +To install musl as an alternate libc, follow these steps: +1. Edit config.mak to select your system's CPU architecture (i386, + x86_64, or arm), installation prefix, location for the dynamic + linker, and other build preferences. -STEP 4: Using the gcc wrapper. +2. Run "make". Parallel build is fully supported, so you can instead + use "make -j3" or so on SMP systems if you like. -musl comes with a script "musl-gcc" (installed in /usr/local/bin by -default) that can be used to compile and link C programs against musl. -It requires a version of gcc with the -wrapper option (gcc 4.x should -work). For example: +3. Run "make install" as a user sufficient privileges to write to the + destination. + +4. Ensure that /etc/ld-musl-$ARCH.path (where $ARCH is replaced by + i386, x86_64, etc. as appropriate) contains the correct search path + for where you intend to install musl-linked shared library files. + This step can be skipped if you disabled dynamic linking. + +After installing, you can use musl via the musl-gcc wrapper. For +example: cat > hello.c <<EOF #include <stdio.h> @@ -52,17 +65,74 @@ EOF musl-gcc hello.c ./a.out -For compiling programs that use autoconf, you'll need to configure -them with a command like this: +To configure autoconf-based program to compile and link against musl, +you may wish to use: + +CC="musl-gcc -D_GNU_SOURCE" ./configure ... + +Correctly-written build systems should not need -D_GNU_SOURCE as part +of $CC, but many programs do not use feature-test macros correctly and +simply assume the compiler will automatically give them the kitchen +sink, so the above command is an easy workaround. + +You will probably also want to use --prefix when building libraries to +ensure that they are installed under the musl prefix and not in the +main host system library directories. + +Finally, it's worth noting that musl's include and lib directories in +the build tree are setup to be usable without installation, if +necessary. Just modify the musl-gcc wrapper's libc_prefix variable to +point to the source/build tree. + + + +== Option 2: Installing musl as the primary C library == + +In this setup, you will need an existing compiler/toolchain. It +shouldnt matter whether it was configured for glibc, uClibc, musl, or +something else entirely, but sometimes gcc can be uncooperative, +especially if the system distributor has built gcc with strange +options. It probably makes the most sense to perform the following +steps inside a chroot setup or on a virtualized machine with the +filesystem containing just a minimal toolchain. + +WARNING: DO NOT DO THIS ON AN EXISTING SYSTEM UNLESS YOU REALLY WANT +TO CONVERT IT TO BE A MUSL-BASED SYSTEM!! + +1. If you are just upgrading an existing version of musl, you can skip + step 1 entirely. Otherwise, move the existing include and lib + directories on your system out of the way. Unless all the binaries + you will need are static-linked, you should edit /etc/ld.so.conf + (or equivalent) and put the new locations of your old libraries in + the search path before you move them, or your system will break + badly and you will not be able to continue. + +2. Edit musl's config.mak and set the installation prefix to the + prefix your compiler toolchain is configured to search, probably + /usr. Set ARCH to match your CPU architecture, and change any other + options as you see fit. + +3. Run "make" to compile musl. + +4. Run "make install" with appropriate privileges. + +5. If you are using gcc and wish to use dynamic linking, find the gcc + directory containing libgcc.a (it should be something like + /usr/lib/gcc/i486-linux-gnu/4.3.5, with the arch and version + possibly different) and look for a specs file there. If none + exists, use "gcc -dumpspecs > specs" to generate a specs file. Find + the dynamic linker (/lib/ld-linux.so.2 or similar) and change it to + "/lib/ld-musl-$ARCH.so.1" (with $ARCH replaced by your CPU arch). + +At this point, musl should be the default libc. Compile a small test +program with gcc and verify (using readelf -a or objdump -x) that the +dynamic linker (program interpreter) is /lib/ld-musl-$ARCH.so.1. If +you're using static linking only, you might instead check the symbols +and look for anything suspicious that would indicate your old glibc or +uClibc was used. -CC=musl-gcc ./configure +When building programs against musl, you may still want to ensure the +appropriate feature test macros get defined, as in: -Be aware that (at present) libraries linked against glibc are unlikely -to be usable, and the musl-gcc wrapper inhibits search of the system -library paths in any case. You'll need to compile any prerequisite -libraries (like ncurses, glib, etc.) yourself. +CC="gcc -D_GNU_SOURCE" ./configure ... -Note: If you want the system headers to behave something like glibc's -and expose the kitchen sink by default, you might want to try -CC="musl-gcc -D_GNU_SOURCE" instead of just CC=musl-gcc. This is -needed for compiling many programs with portability issues. |