This is a diagnostic you might encounter while running ‘make distcheck’.
As explained in Checking the Distribution, ‘make distcheck’ attempts to build and check your package for errors like this one.
‘make distcheck’ will perform a
VPATH build of your
package (see Parallel Build Trees (a.k.a. VPATH Builds)), and then call ‘make distclean’.
Files left in the build directory after ‘make distclean’ has run
are listed after this error.
This diagnostic really covers two kinds of errors:
The former left-over files are not distributed, so the fix is to mark them for cleaning (see What Gets Cleaned), this is obvious and doesn’t deserve more explanations.
The latter bug is not always easy to understand and fix, so let’s
proceed with an example. Suppose our package contains a program for
which we want to build a man page using
help2man produces simple manual pages from the --help
and --version output of other commands (see Overview in The Help2man Manual). Because we don’t want to force our
users to install
help2man, we decide to distribute the
generated man page using the following setup.
# This Makefile.am is bogus. bin_PROGRAMS = foo foo_SOURCES = foo.c dist_man_MANS = foo.1 foo.1: foo$(EXEEXT) help2man --output=foo.1 ./foo$(EXEEXT)
This will effectively distribute the man page. However, ‘make distcheck’ will fail with:
ERROR: files left in build directory after distclean: ./foo.1
Why was foo.1 rebuilt? Because although distributed, foo.1 depends on a non-distributed built file: foo$(EXEEXT). foo$(EXEEXT) is built by the user, so it will always appear to be newer than the distributed foo.1.
‘make distcheck’ caught an inconsistency in our package. Our
intent was to distribute foo.1 so users do not need to install
help2man, however since this rule causes this file to be
always rebuilt, users do need
help2man. Either we
should ensure that foo.1 is not rebuilt by users, or there is
no point in distributing foo.1.
More generally, the rule is that distributed files should never depend on non-distributed built files. If you distribute something generated, distribute its sources.
One way to fix the above example, while still distributing
foo.1 is to not depend on foo$(EXEEXT). For instance,
foo --version and
foo --help do not
change unless foo.c or configure.ac change, we could
write the following Makefile.am:
bin_PROGRAMS = foo foo_SOURCES = foo.c dist_man_MANS = foo.1 foo.1: foo.c $(top_srcdir)/configure.ac $(MAKE) $(AM_MAKEFLAGS) foo$(EXEEXT) help2man --output=foo.1 ./foo$(EXEEXT)
This way, foo.1 will not get rebuilt every time
foo$(EXEEXT) changes. The
make call makes sure
foo$(EXEEXT) is up-to-date before
way to ensure this would be to use separate directories for binaries
and man pages, and set
SUBDIRS so that binaries are built
before man pages.
We could also decide not to distribute foo.1. In this case it’s fine to have foo.1 dependent upon foo$(EXEEXT), since both will have to be rebuilt. However it would be impossible to build the package in a cross-compilation, because building foo.1 involves an execution of foo$(EXEEXT).
Another context where such errors are common is when distributed files are built by tools that are built by the package. The pattern is similar:
distributed-file: built-tools distributed-sources build-command
should be changed to
distributed-file: distributed-sources $(MAKE) $(AM_MAKEFLAGS) built-tools build-command
or you could choose not to distribute distributed-file, if cross-compilation does not matter.
The points made through these examples are worth a summary:
For desperate cases, it’s always possible to disable this check by
distcleancheck_listfiles as documented in Checking the Distribution.
Make sure you do understand the reason why ‘make distcheck’
complains before you do this.
distcleancheck_listfiles is a
way to hide errors, not to fix them. You can always do better.