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143 lines
6.2 KiB
143 lines
6.2 KiB
/// \page atsections Using Sections Within Grammar Files
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///
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/// \section intro Introduction
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///
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/// A C targeted grammar can make use of special annotations within a grammar
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/// file, which are prefixed with the <b>\@</b> character. These sections cause the
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/// the placement of their contents within the generated code at defined points
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/// such as within the generated C header file.
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///
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/// The general form of these annotations is:
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///
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/// \code
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/// section
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/// : '@' (( 'parser' | 'lexer' ) '::')? SECTIONNAME '{' yourcode '}'
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/// ;
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/// \endcode
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///
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/// If the 'parser' or lexer keywords are left out of the specification, then the
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/// ANTLR tool assumes a lexer target for a lexer grammar, a parser target for a parser
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/// or tree parser grammar, and a parser target for a combined lexer/parser grammar. You
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/// are advised as a matter of course to include the parser or lexer target keyword.
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///
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/// Documentation regarding the \@sections available for a grammar targeted at C now
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/// follows.
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///
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/// \subsection psrinit Sections \@init and \@declarations
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///
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/// Java targeted grammars allow the special section <code>\@init</code> to be placed after the declaration
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/// of a rule (lexer, parser and tree parser rules). This allows you to both declare and initialize
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/// variables that are local to the code generated for that rule. You can then reference them within
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/// your rule action code.
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///
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/// With the C target, the generated code is subject to the restrictions of C semantics and this
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/// means that you must declare any local variables, then assign to them afterwards. As well as the
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/// <code>\@init</code> section, which C programmers should use to initialize their local variables, the C
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/// target provides the <code>\@declarations</code> section, which is also a rule based section. This section
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/// is where the C programmer should declare the local variables, thus separating their declaration
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/// from their initialization. Here is an example:
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///
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/// \code
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/// translation_unit
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/// @declarations
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/// {
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/// pANTLR3_BOOLEAN hasUsing;
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/// }
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/// @init
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/// {
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///
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/// // Assume no Using directives
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/// //
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/// hasUsing = ANTLR3_FALSE;
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///
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/// }
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/// : rulea ruleb ...
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///
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/// \endcode
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///
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/// Using the <code>\@declarations</code> and <code>\@init</code> sections guarantees that your generated code will
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/// compile correctly on any standard C compiler (assuming, of course, that you type in valid C code.)
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///
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/// \subsection psrheader \@header section.
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///
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/// The <code>\@parser::header</code> or <code>\@lexer::header</code> annotations cause the code they encapsulate
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/// to be placed at the start of each generated file, regardless of whether it is a .c or .h file. This can
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/// be useful for inserting copyright information and so on in all your generated files.
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///
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/// \bNOTE: Be careful not to confuse this concept with placing code in the generated .h header file. The name choice is
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/// unfortunate, but was already used in the Java target to allow the placement of \c imports statements
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/// in generated java classes. We have therefore kept the intent of this section the same.
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///
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/// Here is an example:
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////
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/// \code
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/// @lexer::header
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/// {
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/// // Copyright (c) Jim Idle 2007 - All your grammar are belong to us.
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/// }
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///
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/// @parser::header
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/// {
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/// // Copyright (c) Jim Idle 2007 - All your grammar are belong to us.
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/// }
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/// \endcode
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///
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///
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/// \subsection hdrinclude \@includes section
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///
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/// The <code>\@parser::includes</code> or <code>\@lexer::includes</code> annotations cause
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/// the code they encapsulate to be placed in the generated .h file, \b after the standard
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/// includes required by the ANTLR generated code.
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///
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/// Here you could for instance place a <code>\#include</code>
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/// statement to cause your grammar code to include some standard definitions. Because you
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/// may use multiple parsers and lexers in your solution, you should probably not place
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/// <code>#define</code> statements here, but in the <code>\@postinclude</code> section. Then you
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/// may create different <code>\#defines</code> for different recognizers.
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///
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/// Here is an example:
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////
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/// \code
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/// @lexer::includes
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/// {
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/// #include "myprojectcommondefs.h"
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/// }
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///
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/// @parser::includes
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/// {
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/// #include "myprojectcommondefs.h"
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/// }
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/// \endcode
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///
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///
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/// \subsection hdrpreinclude \@preincludes section
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///
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/// The <code>\@parser::preincludes</code> or <code>\@lexer::preincludes</code> annotations cause
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/// the code they encapsulate to be placed in the generated .h file, \b before the standard
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/// includes required by the ANTLR generated code.
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///
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/// You should use this section when you wish to place #defines and other definitions
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/// in the code before the standard ANTLR runtime includes defined them. This allows you
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/// to override any predefined symbols and options that the includes otherwise take
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/// defaults for. For instance, if you have built a version of the runtime with a
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/// special version of malloc, you can <code>\#define</code> #ANTLR3_MALLOC to match the definition
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/// you used for the ANTLR runtime library.
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///
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/// \subsection hdrpostinclude \@postinclude section
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///
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/// The <code>\@parser::postinclude</code> or <code>\@lexer::postinclude</code> annotations cause
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/// the code they encapsulate to be placed in the generated <b>.C</b> file, after the generated include
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/// file (which includes the standard ANTLR3C library includes.
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///
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/// Code you place here then will be subject to any macros defined by your own includes, by the
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/// generated include and by the standard ANTLR3 includes. This is a good place to <code>\#undef</code>
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/// anything that you don;t like the default values of, but cannot override before the includes
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/// define them.
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///
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/// This is also a good place to <code>#define</code> any macros you may wish to use in the generated
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/// .c file. As you can include multiple parsers in your projects, you will need to include the
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/// generated .h file of each of them, possibly globally, but almost certainly in a context where you
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/// are including more than one .h file simultaneously. Hence if you commonly use the same macro
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/// names for accessing structures and so on, and they change from grammar to grammar, you should
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/// define them here to avoid creating conflicting definitions in the header files.
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/// |