Index: 0.351/ChangeLog
--- 0.351/ChangeLog Sat, 24 Jun 2000 21:44:31 +0200 akim (ace/34_ChangeLog 1.318 666)
+++ 0.351(w)/ChangeLog Sat, 24 Jun 2000 21:44:36 +0200 akim (ace/34_ChangeLog 1.318
+666)
@@ -5,6 +5,10 @@
2000-06-24 Akim Demaille <[EMAIL PROTECTED]>
+ * doc/autoconf.texi (Prerequisite Macros): More about AC_REQUIRE.
+
+2000-06-24 Akim Demaille <[EMAIL PROTECTED]>
+
Given better names to the diversions.
* acgeneral.m4 (_AC_DIVERT(NORMAL_2), _AC_DIVERT(NORMAL_3),
Index: 0.351/doc/autoconf.texi
--- 0.351/doc/autoconf.texi Tue, 13 Jun 2000 22:59:01 +0200 akim (ace/16_autoconf.t
1.61.2.38 666)
+++ 0.351(w)/doc/autoconf.texi Sat, 24 Jun 2000 21:44:36 +0200 akim (ace/16_autoconf.t
+1.61.2.38 666)
@@ -6200,7 +6200,82 @@ @node Prerequisite Macros, Suggested Ord
with square brackets. @var{macro-name} must have been defined using
@code{AC_DEFUN} or else contain a call to @code{AC_PROVIDE} to indicate
that it has been called.
+
+@code{AC_REQUIRE} must be used inside an @code{AC_DEFUN}'d macro, it
+must not be called from the top level.
@end defmac
+
+@code{AC_REQUIRE} is often misunderstood, it really implements
+dependencies between macros in the sense that if a macro depends upon
+another, the latter will be expanded @emph{before} the body of the
+former. In particular, @samp{AC_REQUIRE(FOO)} is not replaced with the
+body of @code{FOO}. For instance, this definition of macros
+
+@example
+@group
+AC_DEFUN([TRAVOLTA],
+[test "$body_temparature_in_celsius" -gt "38" &&
+ dance_floor=occupied])
+AC_DEFUN([NEWTON_JOHN],
+[test "$hair_style" = "curly" &&
+ dance_floor=occupied])
+@end group
+
+@group
+AC_DEFUN([RESERVE_DANCE_FLOOR],
+[if date | grep '^Sat.*pm' >/dev/null 2>&1; then
+ AC_REQUIRE([TRAVOLTA])
+ AC_REQUIRE([NEWTON_JOHN])
+fi])
+@end group
+@end example
+
+@noindent
+with this @file{configure.in}
+
+@example
+AC_INIT
+RESERVE_DANCE_FLOOR
+if test "$dance_floor" = occupied; then
+ AC_MSG_ERROR([cannot pick up here, let's move])
+fi
+@end example
+
+@noindent
+will not leave you with a better chance to meet the kindred soul the
+other times that the Saturday night since it expands into:
+
+@example
+@group
+test "$body_temperature_in_Celsius" -gt "38" &&
+ dance_floor=occupied
+test "$hair_style" = "curly" &&
+ dance_floor=occupied
+fi
+if date | grep '^Sat.*pm' >/dev/null 2>&1; then
+
+
+fi
+@end group
+@end example
+
+This behavior was chosen on purpose: (i) it avoids that messages from
+required macros interrupt the messages from the requiring macros, (ii),
+it avoids bad surprises when shell conditionals are used, as in:
+
+@example
+@group
+if ...; then
+ AC_REQUIRE([SOME_CHECK])
+fi
+...
+SOME_CHECK
+@end group
+@end example
+
+
+You are encouraged to put all the @code{AC_REQUIRE}s at the beginning of
+the macros. You can use @code{dnl} to avoid the empty line they leave.
An alternative to using @code{AC_DEFUN} is to use @code{define} and call
@code{AC_PROVIDE}. Because this technique does not prevent nested
