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<H1> Semi-dependency on GNU utils </H1>
Some of the features depend on GNU-specific implementation of standard
software. These are all semi-dependencies, which means if an user doesn't
have GNU software on a system, it is still possible for him/her to compile
libmawk. Unfortunately editing some parts of the source on such a system
would not result in the desired updates. Obviously a main goal is to
minimize this sort of dependency, but sometimes it is very hard or impossible
to avoid. This document describes these dependencies explaining the tradeoff
and the ways around.
<H2> 1. Bison </H2>
	<H3> 1.1. Rationale </H3>
		There are four GNU-specific features in use:
		<UL>
			<LI> %pure-parser for getting a reentrant parser
			<LI> %parse-param to pass mawk state around to avoid global variables
			<LI> %lex-param for the same reason as %parse-param
			<LI> --name-prefix to avoid namespace pollution
		</UL>
		The first three features are critical for having a reentrant/thread safe
		libmawk. Without those three, there could be only one mawk context in
		an application, or at least parsing more than one script in the same
		time would cause both context mangled.
		<P>
		The fourth feature, --name-prefix helps avoiding namespace pollution -
		the application may have its own parsers with or without name prefixing,
		and libmawk shouldn't collide with those.

	<H3> 1.2. effects, restrictions </H3>
		Scconfig detects presence of bison; in case bison is not installed,
		Makefile.conf is generated in a way that bison is never run. Output
		of bison is included in the source tree (parse.c/parse.h).
		<P>
		<B>Not having bison on a systam means editing parse.y will not
		update the actual parser code in parse.c</B>.

	<H3> 1.3. how to bypass </H3>
		It is possible to use traditional yacc for compiling parse.y. Besides
		editing Makefile.conf and parse.y for removing those 4 features,
		scan.c/scan.h should be edited too, because arguments for the scanner
		depends on these settings. A global variable for the mawk context for
		the script currently being parsed should be introduced. Actions should
		be made to ensure no concurrent loading of scripts is possible.

<H2> 2. Makefile.dep needs gcc </H2>
	<H3> 2.1. Rationale </H3>
		Source file dependencies are generated using <I>gcc -MM</I> and are
		stored in Makefile.dep shipped with the source package.

	<H3> 2.2. effects, restrictions </H3>
		After changing #include lines in the source, running <I>make depend</I>
		will not update Makefile.dep but will zap it.

	<H3> 2.3. how to bypass </H3>
		It is easily possible to keep Makefile.dep in sync by hand. Another option
		is to ignore Makefile.dep and run <I>make clean</I> before compilation.

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