Makefile Fragments

When you configure GNU CC using the `configure' script (see section Installing GNU CC), it will construct the file `Makefile' from the template file `Makefile.in'. When it does this, it will incorporate makefile fragment files from the `config' directory, named `t-target' and `x-host'. If these files do not exist, it means nothing needs to be added for a given target or host.

The Target Makefile Fragment

The target makefile fragment, `t-target', defines special target dependent variables and targets used in the `Makefile':

LIBGCC1

The rule to use to build `libgcc1.a'. If your target does not need to use the functions in `libgcc1.a', set this to empty. See section Interfacing to GNU CC Output.

CROSS_LIBGCC1

The rule to use to build `libgcc1.a' when building a cross compiler. If your target does not need to use the functions in `libgcc1.a', set this to empty. See section `libgcc.a' and Cross-Compilers.

LIBGCC2_CFLAGS

Compiler flags to use when compiling `libgcc2.c'.

LIB2FUNCS_EXTRA

A list of source file names to be compiled or assembled and inserted into `libgcc.a'.

CRTSTUFF_T_CFLAGS

Special flags used when compiling `crtstuff.c'. See section How Initialization Functions Are Handled.

MULTILIB_OPTIONS

For some targets, invoking GNU CC in different ways produces objects that can not be linked together. For example, for some targets GNU CC produces both big and little endian code. For these targets, you must arrange for multiple versions of `libgcc.a' to be compiled, one for each set of incompatible options. When GNU CC invokes the linker, it arranges to link in the right version of `libgcc.a', based on the command line options used. The MULTILIB_OPTIONS macro lists the set of options for which special versions of `libgcc.a' must be built. Write options that are mutually incompatible side by side, separated by a slash. Write options that may be used together separated by a space. The build procedure will build all combinations of compatible options. For example, if you set MULTILIB_OPTIONS to `m68000/m68020 msoft-float', `Makefile' will build special versions of `libgcc.a' using the options `-m68000', `-m68020', `-msoft-float', `-m68000 -msoft-float', and `-m68020 -msoft-float'.

MULTILIB_DIRNAMES

If MULTILIB_OPTIONS is used, this variable specifies the directory names that should be used to hold the various libraries. Write one element in MULTILIB_DIRNAMES for each element in MULTILIB_OPTIONS. If MULTILIB_DIRNAMES is not used, the default value will be MULTILIB_OPTIONS, with all slashes treated as spaces. For example, if MULTILIB_OPTIONS is `m68000/m68020 msoft-float', then the default value of MULTILIB_DIRNAMES is `m68000 m68020 msoft-float'. You may specify a different value if you desire a different set of directory names.

MULTILIB_MATCHES

Sometimes the same option may be written in two different ways. If an option is listed in MULTILIB_OPTIONS, GNU CC needs to know about any synonyms. In that case, set MULTILIB_MATCHES to a list of items of the form `option=option' to describe all relevant synonyms. For example, `m68000=mc68000 m68020=mc68020'.

The Host Makefile Fragment

The host makefile fragment, `x-host', defines special host dependent variables and targets used in the `Makefile':

CC

The compiler to use when building the first stage.

CLIB

Additional host libraries to link with.

OLDCC

The compiler to use when building `libgcc1.a' for a native compilation.

OLDAR

The version of ar to use when building `libgcc1.a' for a native compilation.

INSTALL

The install program to use.

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