12.15. Avoid Use of the .error Construct

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 節 9.1, “Running make describe). However, even more trivial commands such as make maintainer also fail in this scenario. This is not acceptable.

範例 12.1. How to Avoid Using .error

The 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

本文及其他文件,可由此下載: ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/

若有 FreeBSD 方面疑問,請先閱讀 FreeBSD 相關文件,如不能解決的話,再洽詢 <questions@FreeBSD.org>。

關於本文件的問題,請洽詢 <doc@FreeBSD.org>。