distcc User Manual: distcc Compatibility

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## 3. distcc Compatibility

## 3.1 distcc with ccache

distcc works well with the ccache tool for caching compilation results. To use the two of them together, simply set

> `

>     CC='ccache distcc'

> `

## 3.2 distcc with autoconf

distcc works quite well with autoconf.

`DISTCC_VERBOSE` can give autoconf trouble because autoconf tries to parse error messages from the compiler. If you redirect distcc's diagnostics using `DISTCC_LOG` then it seems to be fine.

Some autoconf-based systems "freeze" the compiler name used for configure into their Makefiles. To make them use distcc, you must either set `$CC` when running `./configure`, and/or override `$CC` on the right-hand-side of the Make command line.

Some poorly-written shell scripts may assume that `$CC` is a single word. At the moment the best fix is to use a shell script that calls `distcc`.

## 3.3 distcc with libtool

Some versions of libtool seem not to cope well when CC is set to more than one word, such as `"distcc gcc"`. Setting `CC=distcc`, which is supported in 0.10 and later, seems to work well.

## 3.4 distcc with Gentoo Linux

Gentoo is a "ports"-based free software distribution, in which packages are always built from source on installation. distcc works well with Gentoo to speed installation.

You can install distcc either using the upstream tarball from `distcc.samba.org` (which may be newer), or using `emerge distcc` to get the Gentoo port, which may be better integrated. You can also get ccache with `emerge ccache`.

After installing distcc, starting servers and setting `DISTCC_HOSTS`, use a command like this to build addition packages using distcc:

> `

>     MAKEOPTS="-j9" CC=distcc CXX=distcc emerge

> packagename`

The `-j9` is only an example; set it appropriately for the number of processors available.

To use distcc for all compilations, edit `/etc/make.conf` to include something like these lines, appropriately adjusted for your systems:

> `

>     CC="distcc"
>     CXX="distcc g++"
>     MAKEOPTS="-j4"
>     DISTCC_HOSTS="host1 host2 localhost"

> `

## 3.5 distcc with gcc dependency computation

gcc has the ability to produce information about header dependencies as a side-effect of preprocessing. These can be included in Makefiles in various ways to make sure that files are up-to-date.

This feature is enabled using `-MD`, `-M` and related options.

Unfortunately, gcc changed the behaviour of this feature between gcc 2.95 and 3.x in such a way that it seems properly for distcc to generally support it. The difficulty is that the filename to which dependencies are written depends in a very complicated way on the gcc command line. distcc needs to change the command line to run the preprocessor locally and the compiler remotely, and this can sometimes cause problems. (This also causes problems for Makefiles that are supposed to work with both versions of the compiler.)

`-M` causes gcc to produce dependency information instead of compiling. distcc understands this and passes the option straight through to gcc. It should work correctly.

With gcc 2.95, `-MD` always writes dependencies into the preprocessor's working directory. distcc should work fine.

With gcc 3.2, `-MD` writes the output into either the source directory or output directory, depending on the presence of the `-o` option. However, gcc 3.2 also has a `-MF` option that can be used to explicitly set the dependency output file, and this works well with distcc.

In summary: for gcc 2.95, no changes are required. For gcc 3.2, `-MF` should be used to specify the file to write dependencies to.

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