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Import AnaGram (near-)release tree into Mercurial.
author David A. Holland
date Sat, 22 Dec 2007 17:52:45 -0500
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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
+
+<HTML>
+<HEAD>
+<TITLE>C Parsers - Macro preprocessor and C Parser </TITLE>
+</HEAD>
+
+
+<BODY BGCOLOR="#ffffff" BACKGROUND="tilbl6h.gif"
+ TEXT="#000000" LINK="#0033CC"
+ VLINK="#CC0033" ALINK="#CC0099">
+
+<P>
+<IMG ALIGN="right" SRC="../../images/agrsl6c.gif" ALT="AnaGram"
+         WIDTH=124 HEIGHT=30 >
+<BR CLEAR="all">
+Back to :
+<A HREF="../../index.html">Index</A> |
+<A HREF="index.html">Macro preprocessor overview</A>
+<P>
+
+
+<IMG ALIGN="bottom" SRC="../../images/rbline6j.gif" ALT="----------------------"
+        WIDTH=1010 HEIGHT=2  >
+<P>
+
+<H1>C Parsers - Macro preprocessor and C Parser   </H1>
+
+<IMG ALIGN="bottom" SRC="../../images/rbline6j.gif" ALT="----------------------"
+        WIDTH=1010 HEIGHT=2  >
+<P>
+<BR>
+
+          Two C grammars are provided with this example: <tt>jrc.syn</tt> is a
+          translation of a <tt>yacc</tt> grammar for C created by James A.
+          Roskind. <tt>krc.syn</tt> is a grammar adapted from Kernighan and
+          Ritchie, Section A13.
+<P>
+          Both grammars use semantically determined productions to
+          distinguish between typedef names and identifiers, however,
+          neither grammar has been adapted to take advantage of this
+          capability to resolve many of the problems associated with
+          typedef names.
+<P>
+          In order to parse simple examples successfully, it was
+          necessary to create a rudimentary capability to recognize
+          typedef names. Such capabilities were incorporated into each
+          grammar. Note that the scope handling is inadequate for
+          production use.
+<P>
+          In <tt>jrc.syn</tt>, the typedef token causes a flag to be set. When
+          the identifier in a declaration is encountered, the flag is
+          interrogated. The complication is the possible interposition
+          of field names within a struct or union which could be
+          inadvertently marked as typedef names. To avoid this, the
+          flag is stored on encountering a struct or union and
+          restored when the danger is past.
+<P>
+          In <tt>krc.syn</tt>, the treatment of typedefs is marginally less
+          inelegant. Storage class attributes are accumulated in a bit
+          mask. As identifiers are encountered in the declaration
+          statement they are pushed onto a multilevel stack, <tt>id_stack</tt>.
+          When struct or union declarations are encountered, the level
+          of the id_stack is incremented. When the danger is past, the
+          level is decremented so that identifiers stacked in the
+          course of parsing the struct or union are discarded.
+          Eventually, when the statement is complete, all the
+          identifiers that have been found are popped from <tt>id_stack</tt>
+          and given the appropriate storage class attribute.
+<P>
+          Both grammars are set up so that the name of the parser is
+          <tt>cc()</tt>.
+          Each
+          syntax file contains member function definitions for the
+          class <tt>c_parser</tt>. They are identical except for the
+          initialization of the typedef logic. The definition of the
+          class <tt>c_parser</tt> is found in <tt>MPP.H</tt>.
+<P>
+          <B>Note:</B> Until AnaGram 2.40, the parsers were set up
+          so both would emit the files <tt>cc.cpp</tt> and
+          <tt>cc.h</tt>. This caused problems for AnaGram 2.40's more
+          automated build and test system. As of this writing,
+          <tt>krc.syn</tt> is used by default; to use <tt>jrc.syn</tt>
+          you must change the <tt>#include</tt> near the top of
+          <tt>mpp.h</tt> to include <tt>jrc.h</tt>. With luck, this
+          annoyance will be cleared up in a future release.
+<P>
+          It should be noted that the KRC grammar has at least one
+          bug. It will not recognize function declarations of the
+          form:
+<PRE>
+            foo(int);
+</PRE>
+          It will, however, recognize
+<PRE>
+            int foo(int);
+</PRE>
+          This problem appears to be inherent in the grammar published
+          in K &amp; R.
+<P>
+<BR>
+
+
+<IMG ALIGN="bottom" SRC="../../images/rbline6j.gif" ALT="----------------------"
+      WIDTH=1010 HEIGHT=2 >
+<P>
+<IMG ALIGN="right" SRC="../../images/pslrb6d.gif" ALT="Parsifal Software"
+                WIDTH=181 HEIGHT=25>
+<BR CLEAR="right">
+
+<P>
+Back to :
+<A HREF="../../index.html">Index</A> |
+<A HREF="index.html">Macro preprocessor overview</A>
+
+<P>
+<ADDRESS><FONT SIZE="-1">
+                  AnaGram parser generator - examples<BR>
+                  C Parsers - Macro preprocessor and C Parser <BR>
+                  Copyright &copy; 1993-1999, Parsifal Software. <BR>
+                  All Rights Reserved.<BR>
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