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In a directory containing source that gets built into a program (as
opposed to a library), the `PROGRAMS' primary is used. Programs
can be installed in bindir, sbindir, libexecdir,
pkglibdir, or not at all (`noinst').
For instance:
bin_PROGRAMS = hello
In this simple case, the resulting `Makefile.in' will contain code
to generate a program named hello. The variable
hello_SOURCES is used to specify which source files get built
into an executable:
hello_SOURCES = hello.c version.c getopt.c getopt1.c getopt.h system.h
This causes each mentioned `.c' file to be compiled into the corresponding `.o'. Then all are linked to produce `hello'.
If `prog_SOURCES' is needed, but not specified, then it defaults to the single file `prog.c'.
Multiple programs can be built in a single directory. Multiple programs can share a single source file, which must be listed in each `_SOURCES' definition.
Header files listed in a `_SOURCES' definition will be included in the distribution but otherwise ignored. In case it isn't obvious, you should not include the header file generated by `configure' in an `_SOURCES' variable; this file should not be distributed. Lex (`.l') and Yacc (`.y') files can also be listed; see section Yacc and Lex support.
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 `EXTRA_' variable. For instance, if
`hello-linux.c' were conditionally included in hello, the
`Makefile.am' would contain:
EXTRA_hello_SOURCES = hello-linux.c
Similarly, sometimes it is useful to determine the programs that are to
be built at configure time. For instance, GNU cpio only builds
mt and rmt under special circumstances.
In this case, you must notify Automake of all the programs that can
possibly be built, but at the same time cause the generated
`Makefile.in' to use the programs specified by configure.
This is done by having configure substitute values into each
`_PROGRAMS' definition, while listing all optionally built programs
in EXTRA_PROGRAMS.
If you need to link against libraries that are not found by
configure, you can use LDADD to do so. This variable
actually can be used to add any options to the linker command line.
Sometimes, multiple programs are built in one directory but do not share
the same link-time requirements. In this case, you can use the
`prog_LDADD' variable (where prog is the name of the
program as it appears in some `_PROGRAMS' variable, and usually
written in lowercase) to override the global LDADD. If this
variable exists for a given program, then that program is not linked
using LDADD.
For instance, in GNU cpio, pax, cpio and mt are
linked against the library `libcpio.a'. However, rmt is
built in the same directory, and has no such link requirement. Also,
mt and rmt are only built on certain architectures. Here
is what cpio's `src/Makefile.am' looks like (abridged):
bin_PROGRAMS = cpio pax @MT@ libexec_PROGRAMS = @RMT@ EXTRA_PROGRAMS = mt rmt LDADD = ../lib/libcpio.a @INTLLIBS@ rmt_LDADD = cpio_SOURCES = ... pax_SOURCES = ... mt_SOURCES = ... rmt_SOURCES = ...
`prog_LDADD' is inappropriate for passing program-specific linker flags (except for `-l' and `-L'). So, use the `prog_LDFLAGS' variable for this purpose.
It is also occasionally useful to have a program depend on some other target which is not actually part of that program. This can be done using the `prog_DEPENDENCIES' variable. Each program depends on the contents of such a variable, but no further interpretation is done.
If `prog_DEPENDENCIES' is not supplied, it is computed by Automake. The automatically-assigned value is the contents of `prog_LDADD', with most configure substitutions, `-l', and `-L' options removed. The configure substitutions that are left in are only `@LIBOBJS@' and `@ALLOCA@'; these are left because it is known that they will not cause an invalid value for `prog_DEPENDENCIES' to be generated.
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