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9.3 Reporting Messages

When macros statically diagnose abnormal situations, benign or fatal, they should report them using these macros. For dynamic issues, i.e., when configure is run, see Printing Messages.

— Macro: AC_DIAGNOSE (category, message)

Report message as a warning (or as an error if requested by the user) if warnings of the category are turned on. You are encouraged to use standard categories, which currently include:

`all'
messages that don't fall into one of the following categories. Use of an empty category is equivalent.
`cross'
related to cross compilation issues.
`obsolete'
use of an obsolete construct.
`syntax'
dubious syntactic constructs, incorrectly ordered macro calls.

— Macro: AC_WARNING (message)

Equivalent to `AC_DIAGNOSE([syntax], message)', but you are strongly encouraged to use a finer grained category.

— Macro: AC_FATAL (message)

Report a severe error message, and have autoconf die.

When the user runs `autoconf -W error', warnings from AC_DIAGNOSE and AC_WARNING are reported as error, see autoconf Invocation.