Automake has somewhat idiosyncratic support for Yacc and Lex.
Automake assumes that the .c file generated by yacc
or lex should be named using the basename of the input
file. That is, for a Yacc source file foo.y, Automake will
cause the intermediate file to be named foo.c (as opposed to
y.tab.c, which is more traditional).
The extension of a Yacc source file is used to determine the extension of the resulting C or C++ source and header files. Be aware that header files are generated only when the option -d is given to Yacc; see below for more information about this flag, and how to specify it. Files with the extension .y will thus be turned into .c sources and .h headers; likewise, .yy will become .cc and .hh, .y++ will become c++ and h++, .yxx will become .cxx and .hxx, and .ypp will become .cpp and .hpp.
Similarly, Lex source files can be used to generate C or C++; the extensions .l, .ll, .l++, .lxx, and .lpp are recognized.
You should never explicitly mention the intermediate (C or C++) file
in any SOURCES variable (except BUILT_SOURCES, see below);
only list the source file.
The intermediate files generated by yacc (or lex)
will be included in any distribution that is made. That way the user
doesn’t need to have yacc or lex.
If a Yacc source file is seen, then your configure.ac must
define the variable YACC. This is most easily done by invoking
the macro AC_PROG_YACC (see Particular Program Checks in The Autoconf Manual).
When yacc is invoked, it is passed AM_YFLAGS and
YFLAGS. The latter is a user variable and the former is
intended for the Makefile.am author.
AM_YFLAGS is usually used to pass the -d option to
yacc. Automake knows what this means and will automatically
adjust its rules to update and distribute the header file built by
‘yacc -d’. Caveat: automake recognizes -d in
AM_YFLAGS only if it is not clustered with other options; for
example, it won’t be recognized if AM_YFLAGS is -dt,
but it will be if AM_YFLAGS is -d -t or -t
-d.
What Automake cannot guess, though, is where this header will be used:
it is up to you to ensure the header gets built before it is first
used. Typically this is necessary in order for dependency tracking to
work when the header is included by another file. The common solution
is listing the header file, and the corresponding C file, in
BUILT_SOURCES (see Built Sources) as follows.
BUILT_SOURCES = parser.h parser.c AM_YFLAGS = -d bin_PROGRAMS = foo foo_SOURCES = ... parser.y ...
If a Lex source file is seen, then your configure.ac must
define the variable LEX. You can use AC_PROG_LEX to do
this (see Particular Program Checks in The Autoconf Manual), but using the AM_PROG_LEX
macro (see Autoconf macros supplied with Automake) is recommended.
When lex is invoked, it is passed AM_LFLAGS and
LFLAGS. The latter is a user variable and the former is
intended for the Makefile.am author.
When AM_MAINTAINER_MODE (see missing and AM_MAINTAINER_MODE) is in effect,
the rebuild rules for distributed Yacc and Lex sources are only used
when maintainer-mode is enabled, or when the files have been
erased.
When Yacc or Lex sources are used, automake -a automatically
installs an auxiliary program called ylwrap in your package
(see Programs automake might require). This program is used by the build rules
to rename the output of these tools, and makes it possible to include
multiple yacc (or lex) source files in a single
directory. This is necessary because Yacc’s output file name is
fixed, and a parallel make could invoke more than one instance of
yacc simultaneously.