7.11 Automatic dependency tracking
As a developer it is often painful to continually update the
`Makefile.in' whenever the include-file dependencies change in a
project. Automake supplies a way to automatically track dependency
changes, and distribute the dependencies in the generated `Makefile.in'.
Currently this support requires the use of GNU `make' and `gcc'. It
might become possible in the future to supply a different dependency
generating program, if there is enough demand. In the meantime, this
mode is enabled by default if any C program or library is defined in
the current directory, so you may get a `Must be a separator' error
from non-GNU make.
When you decide to make a distribution, the `dist' target will
re-run `automake' with `--include-deps' and other options.
Invoking Automake, and Options. This will cause the
previously generated dependencies to be inserted into the generated
`Makefile.in', and thus into the distribution. This step also turns
off inclusion of the dependency generation code, so that those who
download your distribution but don't use GNU `make' and `gcc' will not
When added to the `Makefile.in', the dependencies have all
system-specific dependencies automatically removed. This can be done by
listing the files in `OMIT_DEPENDENCIES'. For instance all references
to system header files are removed by Automake. Sometimes it is useful
to specify that a certain header file should be removed. For instance
if your `configure.in' uses `AM_WITH_REGEX', then any dependency on
`rx.h' or `regex.h' should be removed, because the correct one cannot
be known until the user configures the package.
As it turns out, Automake is actually smart enough to handle the
particular case of the regular expression header. It will also
automatically omit `libintl.h' if `AM_GNU_GETTEXT' is used.
Automatic dependency tracking can be suppressed by putting
`no-dependencies' in the variable `AUTOMAKE_OPTIONS'.
If you unpack a distribution made by `make dist', and you want to
turn on the dependency-tracking code again, simply re-run `automake'.
The actual dependency files are put under the build directory, in a
subdirectory named `.deps'. These dependencies are machine specific.
It is safe to delete them if you like; they will be automatically
recreated during the next build.
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