GCC, the GNU Compiler Collection, includes front ends for C, Objective-C, C , Fortran, Java, and Ada, as well as libraries for these languages (libstdc , libgcj,...).Like most GNU software, GCC must be configured before it can be built. This document describes the recommended configuration procedure for both native and cross targets.We use srcdir to refer to the toplevel source directory for GCC; we use objdir to refer to the toplevel build/object directory.If you obtained the sources via CVS, srcdir must refer to the top gcc directory, the one where the MAINTAINERS can be found, and not its gcc subdirectory, otherwise the build will fail.If either srcdir or objdir is located on an automounted NFS file system, the shell\'s built-in pwd command will return temporary pathnames. Using these can lead to various sorts of build problems. To avoid this issue, set the PWDCMD environment variable to an automounter-aware pwd command, e.g., pawd or `amq -w\', during the configuration and build phases.First, we highly recommend that GCC be built into a separate directory than the sources which does not reside within the source tree. This is how we generally build GCC; building where srcdir == objdir should still work, but doesn\'t get extensive testing; building where objdir is a subdirectory of srcdir is unsupported.If you have previously built GCC in the same directory for a different target machine, do `make distclean\' to delete all files that might be invalid. One of the files this deletes is Makefile; if `make distclean\' complains that Makefile does not exist or issues a message like \"don\'t know how to make distclean\" it probably means that the directory is already suitably clean. However, with the recommended method of building in a separate objdir, you should simply use a different objdir for each target.Second, when configuring a native system, either cc or gcc must be in your path or you must set CC in your environment before running configure. Otherwise the configuration scripts may fail.Note that the bootstrap compiler and the resulting GCC must be link compatible, else the bootstrap will fail with linker errors about incompatible object file formats. Several multilibed targets are affected by this requirement, see host/target specific installation notes.To configure GCC: % mkdir objdir % cd objdir % srcdir/configure [options] [target]Target specification· GCC has code to correctly determine the correct value for target for nearly all native systems. Therefore, we highly recommend you not provide a configure target when configuring a native compiler.· target must be specified as --target=target when configuring a cross compiler; examples of valid targets would be m68k-coff, sh-elf, etc.· Specifying just target instead of --target=target implies that the host defaults to target.