1atsections(3) ANTLR3C atsections(3)
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6 atsections - Using Sections Within Grammar Files
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9 A C targeted grammar can make use of special annotations within a
10 grammar file, which are prefixed with the @ character. These sections
11 cause the the placement of their contents within the generated code at
12 defined points such as within the generated C header file.
13 The general form of these annotations is:
15 section
17 : '@' (( 'parser' | 'lexer' ) '::')? SECTIONNAME '{' yourcode '}'
18 ;
19 If the 'parser' or lexer keywords are left out of the specification,
21 then the ANTLR tool assumes a lexer target for a lexer grammar, a
22 parser target for a parser or tree parser grammar, and a parser target
23 for a combined lexer/parser grammar. You are advised as a matter of
24 course to include the parser or lexer target keyword.
25 Documentation regarding the @sections available for a grammar targeted
27 at C now follows.
28 Sections @init and @declarations
30 Java targeted grammars allow the special section @init to be placed
31 after the declaration of a rule (lexer, parser and tree parser rules).
32 This allows you to both declare and initialize variables that are local
33 to the code generated for that rule. You can then reference them within
34 your rule action code.
35 With the C target, the generated code is subject to the restrictions of
37 C semantics and this means that you must declare any local variables,
38 then assign to them afterwards. As well as the @init section, which C
39 programmers should use to initialize their local variables, the C
40 target provides the @declarations section, which is also a rule based
41 section. This section is where the C programmer should declare the
42 local variables, thus separating their declaration from their
43 initialization. Here is an example:
44 translation_unit
46 @declarations
47 {
48 pANTLR3_BOOLEAN hasUsing;
49 }
50 @init
51 {
52 // Assume no Using directives
54 //
55 hasUsing = ANTLR3_FALSE;
56 }
58 : rulea ruleb ...
59 Using the @declarations and @init sections guarantees that your
61 generated code will compile correctly on any standard C compiler
62 (assuming, of course, that you type in valid C code.)
63 @header section.
65 The @parser::header or @lexer::header annotations cause the code they
66 encapsulate to be placed at the start of each generated file,
67 regardless of whether it is a .c or .h file. This can be useful for
68 inserting copyright information and so on in all your generated files.
69 \bNOTE: Be careful not to confuse this concept with placing code in the
71 generated .h header file. The name choice is unfortunate, but was
72 already used in the Java target to allow the placement of imports
73 statements in generated java classes. We have therefore kept the intent
74 of this section the same.
75 Here is an example:
77 @lexer::header
79 {
80 // Copyright (c) Jim Idle 2007 - All your grammar are belong to us.
81 }
82 @parser::header
84 {
85 // Copyright (c) Jim Idle 2007 - All your grammar are belong to us.
86 }
87 @includes section
89 The @parser::includes or @lexer::includes annotations cause the code
90 they encapsulate to be placed in the generated .h file, after the
91 standard includes required by the ANTLR generated code.
92 Here you could for instance place a #include statement to cause your
94 grammar code to include some standard definitions. Because you may use
95 multiple parsers and lexers in your solution, you should probably not
96 place #define statements here, but in the @postinclude section. Then
97 you may create different #defines for different recognizers.
98 Here is an example:
100 @lexer::includes
102 {
103 #include "myprojectcommondefs.h"
104 }
105 @parser::includes
107 {
108 #include "myprojectcommondefs.h"
109 }
110 @preincludes section
112 The @parser::preincludes or @lexer::preincludes annotations cause the
113 code they encapsulate to be placed in the generated .h file, before the
114 standard includes required by the ANTLR generated code.
115 You should use this section when you wish to place #defines and other
117 definitions in the code before the standard ANTLR runtime includes
118 defined them. This allows you to override any predefined symbols and
119 options that the includes otherwise take defaults for. For instance, if
120 you have built a version of the runtime with a special version of
121 malloc, you can #define ANTLR3_MALLOC to match the definition you used
122 for the ANTLR runtime library.
123 @postinclude section
125 The @parser::postinclude or @lexer::postinclude annotations cause the
126 code they encapsulate to be placed in the generated .C file, after the
127 generated include file (which includes the standard ANTLR3C library
128 includes.
129 Code you place here then will be subject to any macros defined by your
131 own includes, by the generated include and by the standard ANTLR3
132 includes. This is a good place to #undef anything that you don;t like
133 the default values of, but cannot override before the includes define
134 them.
135 This is also a good place to #define any macros you may wish to use in
137 the generated .c file. As you can include multiple parsers in your
138 projects, you will need to include the generated .h file of each of
139 them, possibly globally, but almost certainly in a context where you
140 are including more than one .h file simultaneously. Hence if you
141 commonly use the same macro names for accessing structures and so on,
142 and they change from grammar to grammar, you should define them here to
143 avoid creating conflicting definitions in the header files.
144Version 3.3.1 Wed Jan 18 2023 atsections(3)