@node A Program, A Library, Programs, Programs
@section Building a program
-@subsection Introductory blathering
+In order to build a program, you need to tell Automake which sources
+are part of it, and which libraries it should be linked with.
+
+This section also covers conditional compilation of sources or
+programs. Most of the comments about these also apply to libraries
+(@pxref{A Library}) and Libtool libraries (@pxref{A Shared Library}).
+
+@menu
+* Program Sources:: Defining program sources
+* Linking:: Linking with libraries or extra objects
+* Conditional Sources:: Handling conditional sources
+* Conditional Programs:: Building program conditionally
+@end menu
+
+@node Program Sources, Linking, A Program, A Program
+@subsection Defining program sources
@cindex PROGRAMS, bindir
@vindex bin_PROGRAMS
(@samp{.l}) and Yacc (@samp{.y}) files can also be listed; see @ref{Yacc
and Lex}.
-@subsection Conditional compilations
-
-You can't put a configure substitution (e.g., @samp{@@FOO@@}) into a
-@samp{_SOURCES} variable. The reason for this is a bit hard to explain,
-but suffice to say that it simply won't work. Automake will give an
-error if you try to do this.
-
-@cindex EXTRA_prog_SOURCES, defined
-
-Automake must know all the source files that could possibly go into a
-program, even if not all the files are built in every circumstance.
-Any files which are only conditionally built should be listed in the
-appropriate @samp{EXTRA_} variable. For instance, if
-@file{hello-linux.c} were conditionally included in @code{hello}, the
-@file{Makefile.am} would contain:
-
-@example
-EXTRA_hello_SOURCES = hello-linux.c
-@end example
-
-In this case, @file{hello-linux.o} would be added, via a
-@file{configure} substitution, to @code{hello_LDADD} in order to cause
-it to be built and linked in.
-
-An often simpler way to compile source files conditionally is to use
-Automake conditionals. For instance, you could use this construct to
-conditionally use @file{hello-linux.c} or @file{hello-generic.c} as the
-basis for your program @file{hello}:
-
-@example
-if LINUX
-hello_SOURCES = hello-linux.c
-else
-hello_SOURCES = hello-generic.c
-endif
-@end example
-
-When using conditionals like this you don't need to use the
-@samp{EXTRA_} variable, because Automake will examine the contents of
-each variable to construct the complete list of source files.
-
-Sometimes it is useful to determine the programs that are to be built at
-configure time. For instance, GNU @code{cpio} only builds @code{mt} and
-@code{rmt} under special circumstances.
-
-@cindex EXTRA_PROGRAMS, defined
-
-In this case, you must notify Automake of all the programs that can
-possibly be built, but at the same time cause the generated
-@file{Makefile.in} to use the programs specified by @code{configure}.
-This is done by having @code{configure} substitute values into each
-@samp{_PROGRAMS} definition, while listing all optionally built programs
-in @code{EXTRA_PROGRAMS}.
-@vindex EXTRA_PROGRAMS
-
-Of course you can use Automake conditionals to determine the programs to
-be built.
+@node Linking, Conditional Sources, Program Sources, A Program
@subsection Linking the program
If you need to link against libraries that are not found by
generated.
+@node Conditional Sources, Conditional Programs, Linking, A Program
+@subsection Conditional compilation of sources
+
+You can't put a configure substitution (e.g., @samp{@@FOO@@}) into a
+@samp{_SOURCES} variable. The reason for this is a bit hard to explain,
+but suffice to say that it simply won't work. Automake will give an
+error if you try to do this.
+
+Fortunatly there are two other ways to achieve the same result. One is
+to use configure substitutions in @code{_LDADD} variables, the other is
+to use an Automake conditional.
+
+@subsubsection Conditional compilation using @code{_LDADD} substitutions
+
+@cindex EXTRA_prog_SOURCES, defined
+
+Automake must know all the source files that could possibly go into a
+program, even if not all the files are built in every circumstance. Any
+files which are only conditionally built should be listed in the
+appropriate @samp{EXTRA_} variable. For instance, if
+@file{hello-linux.c} or @file{hello-generic.c} were conditionally included
+in @code{hello}, the @file{Makefile.am} would contain:
+
+@example
+bin_PROGRAMS = hello
+hello_SOURCES = hello-common.c
+EXTRA_hello_SOURCES = hello-linux.c hello-generic.c
+hello_LDADD = @@HELLO_SYSTEM@@
+hello_DEPENDENCIES = @@HELLO_SYSTEM@@
+@end example
+
+@noindent
+You can then setup the @code{@@HELLO_SYSTEM@@} substitution from
+@file{configure.in}:
+
+@example
+...
+case $host in
+ *linux*) HELLO_SYSTEM='hello-linux.$(OBJEXT)' ;;
+ *) HELLO_SYSTEM='hello-generic.$(OBJEXT)' ;;
+esac
+AC_SUBST([HELLO_SYSTEM])
+...
+@end example
+
+In this case, @code{HELLO_SYSTEM} should be replaced by
+@file{hello-linux.o} or @file{hello-bsd.o}, and added to
+@code{hello_DEPENDENCIES} and @code{hello_LDADD} in order to be built
+and linked in.
+
+@subsubsection Conditional compilation using Automake conditionals
+
+An often simpler way to compile source files conditionally is to use
+Automake conditionals. For instance, you could use this
+@file{Makefile.am} construct to build the same @file{hello} example:
+
+@example
+bin_PROGRAMS = hello
+if LINUX
+hello_SOURCES = hello-linux.c hello-common.c
+else
+hello_SOURCES = hello-generic.c hello-common.c
+endif
+@end example
+
+In this case, your @file{configure.in} should setup the @code{LINUX}
+conditional using @code{AM_CONDITIONAL} (@pxref{Conditionals}).
+
+When using conditionals like this you don't need to use the
+@samp{EXTRA_} variable, because Automake will examine the contents of
+each variable to construct the complete list of source files.
+
+If your program uses a lot of files, you will probably prefer to use an
+intermediate variable to hold conditional sources.
+
+@example
+bin_PROGRAMS = hello
+if LINUX
+hello_cond = hello-linux.c
+else
+hello_cond = hello-generic.c
+endif
+hello_SOURCES = hello-common.c $(hello_cond)
+@end example
+
+@node Conditional Programs, , Conditional Sources, A Program
+@subsection Conditional compilation of programs
+
+Sometimes it is useful to determine the programs that are to be built at
+configure time. For instance, GNU @code{cpio} only builds @code{mt} and
+@code{rmt} under special circumstances.
+
+@cindex EXTRA_PROGRAMS, defined
+
+In this case, you must notify Automake of all the programs that can
+possibly be built, but at the same time cause the generated
+@file{Makefile.in} to use the programs specified by @code{configure}.
+This is done by having @code{configure} substitute values into each
+@samp{_PROGRAMS} definition, while listing all optionally built programs
+in @code{EXTRA_PROGRAMS}.
+@vindex EXTRA_PROGRAMS
+
+Of course you can use Automake conditionals to determine the programs to
+be built.
+
+
@node A Library, A Shared Library, A Program, Programs
@section Building a library
@end example
This trivial example could also be handled using EXTRA_PROGRAMS
-(@pxref{A Program}).
+(@pxref{Conditional Programs}).
You may only test a single variable in an @code{if} statement, possibly
negated using @samp{!}. The @code{else} statement may be omitted.
git://sourceware.org / automake.git / commitdiff