Bison Syntax Error Unexpected
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Bison Syntax Error Unexpected Identifier Expecting String
I am writing a parser for a toy programming language using bison, but I have hit a wall: My grammar.y file is the following: %{ #include
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up bison unexpected identifier error up vote -1 down vote favorite I'm getting an "unexpected identifier error", at 1-9, on the line string_op | string_lit { $$ = $1; } here is my grammar %union { int intval; double dubval; char* strval; obj object; } %token
topics Evaluation software Community Events Search developerWorks developerWorksTechnical topicsLinuxTechnical library Better error handling using Flex and BisonTips for building more user-friendly compilers and interpreters Although it is http://www.ibm.com/developerworks/library/l-flexbison/ easy to generate programs using Flex and Bison, it is a bit https://www.gnu.org/s/bison/manual/html_node/Error-Reporting.html harder to make those programs produce user-friendly syntax and semantic error messages. This article examines the error-handling features of Flex and Bison, shows how to use them, and details some pitfalls. PDF (209 KB) | Share: Christian Hagen (chagen@de.ibm.com), Senior IT Architect, IBM Close [x] syntax error Christian Hagen is a Senior IT Architect with IBM Global Business Services, Application Services. Although he works as an IT architect, he likes to go back to the basics and do some programming. 28 July 2006 Also available inRussian Table of contents Introduction Sample source files Sample with plain error messages Extending Bison for better error syntax error unexpected messages A better input function Bison's location mechanism Conclusion Download Resources Comments IntroductionAs UNIX® developers know, Flex and Bison are powerful tools for developing lexical and grammar parsers, in particular language compilers and interpreters. If you're unfamiliar with these utilities or the tools they implement -- Lex and Yacc, respectively -- check the Resources section in this article for links to the Flex and Bison documentation and to additional articles that introduce both programs.This article covers a somewhat more advanced topic: features and techniques for putting better error-handling capabilities into your compiler or interpreter. To illustrate these techniques, I use a sample program called ccalc, which implements an enhanced calculator based on the infix calculator from the Bison handbook. You can download ccalc and associated files from the Download section at the end of this article.The enhancements include the use of variables. In ccalc, a variable is defined through its first use in an initialization such as a = 3. If a variable is used before it i
An action in the grammar can also explicitly proclaim an error, using the macro YYERROR (see Special Features for Use in Actions). The Bison parser expects to report the error by calling an error reporting function named yyerror, which you must supply. It is called by yyparse whenever a syntax error is found, and it receives one argument. For a syntax error, the string is normally "syntaxerror". If you invoke ‘%define parse.error verbose’ in the Bison declarations section (see The Bison Declarations Section), then Bison provides a more verbose and specific error message string instead of just plain "syntaxerror". However, that message sometimes contains incorrect information if LAC is not enabled (see LAC). The parser can detect one other kind of error: memory exhaustion. This can happen when the input contains constructions that are very deeply nested. It isn’t likely you will encounter this, since the Bison parser normally extends its stack automatically up to a very large limit. But if memory is exhausted, yyparse calls yyerror in the usual fashion, except that the argument string is "memoryexhausted". In some cases diagnostics like "syntaxerror" are translated automatically from English to some other language before they are passed to yyerror. See Internationalization. The following definition suffices in simple programs: void yyerror (char const *s) { fprintf (stderr, "%s\n", s); } After yyerror returns to yyparse, the latter will attempt error recovery if you have written suitable error recovery grammar rules (see Error Recovery). If recovery is impossible, yyparse will immediately return 1. Obviously, in location tracking pure parsers, yyerror should have an access to the current location. With %define api.pure, this is indeed the case for the GLR parsers, but not for the Yacc parser, for historical reasons, and this is the why %define api.pure full should be prefered over %define api.pure. When %locatio