# Configuring egcs

Like most GNU software, egcs must be configured before it can be built. This document attempts to describe the recommended configuration procedure for both native and cross targets.

We use srcdir to refer to the toplevel source directory for egcs; we use objdir to refer to the toplevel build/object directory for egcs.

First, we highly recommend that egcs be built into a separate directory than the sources which does not reside within the source tree. This is how we generally build egcs; building where srcdir == objdir should still work, but doesn't get extensive testing; building where objdir is a subdirectory of srcdir is unsupported.

Second, when configuring a native system, either "cc" must be in your path or you must set CC in your environment before running configure. Otherwise the configuration scripts may fail.

To configure egcs:

> `
> % mkdir objdir
> % cd objdir
> % srcdir/configure [target] [options]`

target specification

- egcs 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 when configuring a cross compiler; examples of valid targets would be i960-rtems, m68k-coff, sh-elf, etc.

options specification

Use options to override several configure time options for egcs. A partial list of supported `options`:

- `--prefix=`dirname -- Specify the toplevel installation directory. This is the recommended way to install the tools into a directory other than the default. The toplevel installation directory defaults to /usr/local.
  These additional options control where certain parts of the distribution are installed. Normally you should not need to use these options.
  - `--with-local-prefix=`dirname -- Specify the installation directory for local include files. The default is /usr/local.
  - `--with-gxx-include-dir=`dirname -- Specify the installation directory for g++ header files. The default is /usr/local/include/g++.
- `--enable-shared` -- Build shared versions of the C++ runtime libraries if supported `--disable-shared` is the default.
- `--enable-haifa` -- Enable the new Haifa instruction scheduler in the compiler; the new scheduler can significantly improve code on some targets.
  For egcs-1.0.x releases `--disable-haifa` is the default on all platforms except the HPPA.
  For newer releases `--disable-haifa` is the default on all platforms except the alpha, hppa, powerpc, rs6000, sparc and m32r.
- `--with-gnu-as` -- Specify that the compiler should assume the GNU assembler (aka gas) is available.
- `--with-gnu-ld` -- Specify that the compiler should assume the GNU linker (aka gld) is available.
- `--with-stabs` -- Specify that stabs debugging information should be used instead of whatever format the host normally uses. Normally GCC uses the same debug format as the host system.
- `--enable-multilib` -- Specify that multiple target libraries should be built to support different target variants, calling conventions, etc. This is the default.
- `--enable-threads` -- Specify that the target supports threads. This only effects the Objective-C compiler and runtime library.
- `--enable-threads=`lib -- Specify that lib is the thread support library. This only effects the Objective-C compiler and runtime library.
- `--with-cpu=`cpu -- Specify which cpu variant the compiler should generate code for by default. This is currently only supported on the RS6000/PowerPC ports.

Some options which only apply to building cross compilers:

- `--with-headers=`dir -- Specifies a directory which has target include files.
- `--with-libs=`dirs -- Specifies a list of directories which contain the target runtime libraries.
- `--with-newlib` -- Specifies that "newlib" is being used as the target C library. This causes __eprintf to be omitted from libgcc.a on the assumption that it will be provided by newlib.

Note that each `--enable` option has a corresponding `--disable` option and that each `--with` option has a corresponding `--without` option.

Last modified on May 7, 1998.