configure scripts need to give users running them several kinds
of information. The following macros print messages in ways appropriate
for each kind. The arguments to all of them get enclosed in shell
double quotes, so the shell performs variable and backquote substitution
on them. You can print a message containing a comma by quoting the
message with the m4 quote characters:
AC_MSG_RESULT([never mind, I found the BASIC compiler])
These macros are all wrappers around the echo shell command.
configure scripts should rarely need to run echo directly
to print messages for the user. Using these macros makes it easy to
change how and when each kind of message is printed; such changes need
only be made to the macro definitions, and all of the callers change
automatically.
configure is checking for a particular
feature. This macro prints a message that starts with `checking '
and ends with `...' and no newline. It must be followed by a call
to AC_MSG_RESULT to print the result of the check and the
newline. The feature-description should be something like
`whether the Fortran compiler accepts C++ comments' or `for
c89'.
This macro prints nothing if configure is run with the
`--quiet' or `--silent' option.
AC_MSG_CHECKING, and the result-description should be
the completion of the message printed by the call to
AC_MSG_CHECKING.
This macro prints nothing if configure is run with the
`--quiet' or `--silent' option.
configure from
completing. This macro prints an error message on the standard error
output and exits configure with a nonzero status.
error-description should be something like `invalid value
$HOME for \$HOME'.
configure user of a possible problem. This macro
prints the message on the standard error output; configure
continues running afterward, so macros that call AC_MSG_WARN should
provide a default (back-up) behavior for the situations they warn about.
problem-description should be something like `ln -s seems to
make hard links'.
The following two macros are an obsolete alternative to
AC_MSG_CHECKING and AC_MSG_RESULT.
AC_MSG_CHECKING, except that it prints a
newline after the feature-description. It is useful mainly to
print a general description of the overall purpose of a group of feature
checks, e.g.,
AC_CHECKING(if stack overflow is detectable)
AC_MSG_RESULT, except that it is meant
to follow a call to AC_CHECKING instead of
AC_MSG_CHECKING; it starts the message it prints with a tab. It
is considered obsolete.
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