15.5 Controlling Checking of configure Options

The configure script checks its command-line options against a list of known options, like --help or --config-cache. An unknown option ordinarily indicates a mistake by the user and configure halts with an error. However, by default unknown --with-package and --enable-feature options elicit only a warning, to support configuring entire source trees.

Source trees often contain multiple packages with a top-level configure script that uses the AC_CONFIG_SUBDIRS macro (see Subdirectories). Because the packages generally support different --with-package and --enable-feature options, the GNU Coding Standards say they must accept unrecognized options without halting. Even a warning message is undesirable here, so AC_CONFIG_SUBDIRS automatically disables the warnings.

This default behavior may be modified in two ways. First, the installer can invoke configure --disable-option-checking to disable these warnings, or invoke configure --enable-option-checking=fatal options to turn them into fatal errors, respectively. Second, the maintainer can use AC_DISABLE_OPTION_CHECKING.

Macro: AC_DISABLE_OPTION_CHECKING

By default, disable warnings related to any unrecognized --with-package or --enable-feature options. This is implied by AC_CONFIG_SUBDIRS.

The installer can override this behavior by passing --enable-option-checking (enable warnings) or --enable-option-checking=fatal (enable errors) to configure.