The correct way for a Makefile to
signal that the port cannot be installed due to some external
factor (for instance, the user has specified an illegal
combination of build options) is to set a non-blank value to
IGNORE. This value will be formatted and
shown to the user by make install.
It is a common mistake to use .error
for this purpose. The problem with this is that many automated
tools that work with the ports tree will fail in this situation.
The most common occurrence of this is seen when trying to build
/usr/ports/INDEX (see
Section 9.1, “Running make describe”). However, even more trivial
commands such as make maintainer also fail in
this scenario. This is not acceptable.
.errorThe first of the
next two Makefile snippets will cause
make index to fail, while the second one
will not:
.error "option is not supported"
IGNORE=option is not supported
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