1atsections(3) ANTLR3C atsections(3)
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6 atsections - Using Sections Within Grammar Files
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10 A C targeted grammar can make use of special annotations within a
11 grammar file, which are prefixed with the @ character. These sections
12 cause the the placement of their contents within the generated code at
13 defined points such as within the generated C header file.
14 The general form of these annotations is:
16 section
18 : '@' (( 'parser' | 'lexer' ) '::')? SECTIONNAME '{' yourcode '}'
19 ;
20 If the 'parser' or lexer keywords are left out of the specification,
22 then the ANTLR tool assumes a lexer target for a lexer grammar, a
23 parser target for a parser or tree parser grammar, and a parser target
24 for a combined lexer/parser grammar. You are advised as a matter of
25 course to include the parser or lexer target keyword.
26 Documentation regarding the @sections available for a grammar targeted
28 at C now follows.
29 Sections @init and @declarations
31 Java targeted grammars allow the special section @init to be placed
32 after the declaration of a rule (lexer, parser and tree parser rules).
33 This allows you to both declare and initialize variables that are local
34 to the code generated for that rule. You can then reference them within
35 your rule action code.
36 With the C target, the generated code is subject to the restrictions of
38 C semantics and this means that you must declare any local variables,
39 then assign to them afterwards. As well as the @init section, which C
40 programmers should use to initialize their local variables, the C
41 target provides the @declarations section, which is also a rule based
42 section. This section is where the C programmer should declare the
43 local variables, thus separating their declaration from their
44 initialization. Here is an example:
45 translation_unit
47 @declarations
48 {
49 pANTLR3_BOOLEAN hasUsing;
50 }
51 @init
52 {
53 // Assume no Using directives
55 //
56 hasUsing = ANTLR3_FALSE;
57 }
59 : rulea ruleb ...
60 Using the @declarations and @init sections guarantees that your
62 generated code will compile correctly on any standard C compiler
63 (assuming, of course, that you type in valid C code.)
64 @header section.
66 The @parser::header or @lexer::header annotations cause the code they
67 encapsulate to be placed at the start of each generated file,
68 regardless of whether it is a .c or .h file. This can be useful for
69 inserting copyright information and so on in all your generated files.
70 \bNOTE: Be careful not to confuse this concept with placing code in the
72 generated .h header file. The name choice is unfortunate, but was
73 already used in the Java target to allow the placement of imports
74 statements in generated java classes. We have therefore kept the intent
75 of this section the same.
76 Here is an example:
78 @lexer::header
80 {
81 // Copyright (c) Jim Idle 2007 - All your grammar are belong to us.
82 }
83 @parser::header
85 {
86 // Copyright (c) Jim Idle 2007 - All your grammar are belong to us.
87 }
88 @includes section
90 The @parser::includes or @lexer::includes annotations cause the code
91 they encapsulate to be placed in the generated .h file, after the
92 standard includes required by the ANTLR generated code.
93 Here you could for instance place a #include statement to cause your
95 grammar code to include some standard definitions. Because you may use
96 multiple parsers and lexers in your solution, you should probably not
97 place #define statements here, but in the @postinclude section. Then
98 you may create different #defines for different recognizers.
99 Here is an example:
101 @lexer::includes
103 {
104 #include "myprojectcommondefs.h"
105 }
106 @parser::includes
108 {
109 #include "myprojectcommondefs.h"
110 }
111 @preincludes section
113 The @parser::preincludes or @lexer::preincludes annotations cause the
114 code they encapsulate to be placed in the generated .h file, before the
115 standard includes required by the ANTLR generated code.
116 You should use this section when you wish to place #defines and other
118 definitions in the code before the standard ANTLR runtime includes
119 defined them. This allows you to override any predefined symbols and
120 options that the includes otherwise take defaults for. For instance, if
121 you have built a version of the runtime with a special version of
122 malloc, you can #define ANTLR3_MALLOC to match the definition you used
123 for the ANTLR runtime library.
124 @postinclude section
126 The @parser::postinclude or @lexer::postinclude annotations cause the
127 code they encapsulate to be placed in the generated .C file, after the
128 generated include file (which includes the standard ANTLR3C library
129 includes.
130 Code you place here then will be subject to any macros defined by your
132 own includes, by the generated include and by the standard ANTLR3
133 includes. This is a good place to #undef anything that you don;t like
134 the default values of, but cannot override before the includes define
135 them.
136 This is also a good place to #define any macros you may wish to use in
138 the generated .c file. As you can include multiple parsers in your
139 projects, you will need to include the generated .h file of each of
140 them, possibly globally, but almost certainly in a context where you
141 are including more than one .h file simultaneously. Hence if you
142 commonly use the same macro names for accessing structures and so on,
143 and they change from grammar to grammar, you should define them here to
144 avoid creating conflicting definitions in the header files.
145Version 3.3.1 Tue Jan 26 2021 atsections(3)