- Fix ylwrap so that it does not overwrite header files that haven't
changed, as the inline rule already does.
+ - User-defined rules override automake-defined rules for the same
+ targets, even when rules do not have commands. This is not new
+ (and was documented), however some of the automake-generated
+ rules have escaped this principle in former Automake versions.
+ Rules for the following targets are affected by this fix:
+
+ clean, clean-am, dist-all, distclean, distclean-am, dvi, dvi-am,
+ info, info-am, install-data-am, install-exec-am, install-info,
+ install-info-am, install-man, installcheck-am, maintainer-clean,
+ maintainer-clean-am, mostlyclean, mostlyclean-am, pdf, pdf-am,
+ ps, ps-am, uninstall-am, uninstall-info, uninstall-man
+
+ Practically it means that an attempt to supplement the dependencies
+ of some target, as in
+
+ clean: my-clean-rule
+
+ will now *silently override* the automake definition of the
+ rule for this target. Running `automake -Woverride' will diagnose
+ all such overriding definitions.
+
+ It should be noted that almost all these targets support a *-local
+ variant that is meant to supplement the automake-defined rule
+ (See node `Extending' in the manual). The above rule should
+ be rewritten as
+
+ clean-local: my-clean-rule
+
+ These *-local targets have been documented since at least
+ Automake 1.2, so you should not fear the change if you have
+ to support multiple automake versions.
+
* Miscellaneous
- The Automake manual is now distributed under the terms of the GNU FDL.
@node Extending
@chapter When Automake Isn't Enough
-Automake's implicit copying semantics means that many problems can be
-worked around by simply adding some @code{make} targets and rules to
-@file{Makefile.in}. Automake will ignore these additions.
+With some minor exceptions (like @code{_PROGRAMS} variables being
+rewritten to append @code{$(EXEEXT)}), the contents of a
+@file{Makefile.am} is copied to @file{Makefile.in} verbatim.
+
+@cindex copying semantics
+
+These copying semantics means that many problems can be worked around
+by simply adding some @code{make} variables and rules to
+@file{Makefile.am}. Automake will ignore these additions.
+
+@cindex conflicting definitions
+@cindex rules, conflicting
+@cindex variables, conflicting
+@cindex definitions, conflicts
+
+Since a @file{Makefile.in} is built from data gathered from three
+different places (@file{Makefile.am}, @file{configure.ac}, and
+@command{automake} itself), it is possible to have conflicting
+definitions of rules or variables. When building @file{Makefile.in}
+the following priorities are respected by @command{automake} to ensure
+the user always have the last word. User defined variables in
+@file{Makefile.am} have priority over variables @code{AC_SUBST}ed from
+@file{configure.ac}, and @code{AC_SUBST}ed variables have priority
+over @command{automake}-defined variables. As far rules are
+concerned, a user-defined rule overrides any
+@command{automake}-defined rule for the same target.
+
+@cindex overriding rules
+@cindex overriding semantics
+@cindex rules, overriding
+
+These overriding semantics make it possible to fine tune some default
+settings of Automake, or replace some of its rules. Overriding
+Automake rules is often inadvisable, particularly in the topmost
+directory of a package with subdirectories. The @code{-Woverride}
+option (@pxref{Invoking Automake}) comes handy to catch overridden
+definitions.
+
+Note that Automake does not make any difference between rules with
+commands and rules that only specify dependencies. So it is not
+possible to append new dependencies to an @code{automake}-defined
+target without redefining the entire rule.
@cindex -local targets
@cindex local targets
-There are some caveats to doing this. Although you can overload a
-target already used by Automake, it is often inadvisable, particularly
-in the topmost directory of a package with subdirectories. However,
-various useful targets have a @samp{-local} version you can specify in
-your @file{Makefile.in}. Automake will supplement the standard target
-with these user-supplied targets.
+However, various useful targets have a @samp{-local} version you can
+specify in your @file{Makefile.in}. Automake will supplement the
+standard target with these user-supplied targets.
@trindex all
@trindex all-local
git://sourceware.org / automake.git / commitdiff