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Funny Drawing with 'C++' 'FLEX' and a Bison

Published Flex Bison C++ Example 0.1.4

Posted on 2009-09-05 10:40 by Timo Bingmann at Permlink with 0 Comments. Tags: flex-bison-cpp-example c++ code-example

Released a minor updated source code version for Flex Bison C++ Example. The example source code is released into the public domain or, at your option, under the Do What The Fuck You Want To Public License (WTFPL).

This minor bugfix release fixes up two simple compilation issues with the newest bison version 2.4.1.

For more information and the download package see the Flex Bison C++ Example web page.


Funny Drawing with 'C++' 'FLEX' and a Bison

Published Flex Bison C++ Example 0.1.3

Posted on 2008-10-23 11:25 by Timo Bingmann at Permlink with 0 Comments. Tags: flex-bison-cpp-example c++ code-example

Released yet another updated source code package for Flex Bison C++ Example. The example source code is released into the public domain or, at your option, under the Do What The Fuck You Want To Public License (WTFPL).

This bugfix release solves a subtle, severe bug, which rendered the template code useless. Even the example exprtext program segfaulted with any expression.

Corrected a very subtle bug with the newly introduced virtual yywrap() function in the FlexLexer class. Depending on how the header was included, the class contained the virtual yywrap() function or not. These differing class declarations lead to very strange NULL pointer exceptions, because the different compiled objects assume different class memory layouts. Ultimately the exprtest program always segfaulted.

For more information and the download package see the Flex Bison C++ Example web page.


Funny Drawing with 'C++' 'FLEX' and a Bison

Published Flex Bison C++ Example 0.1.2

Posted on 2008-08-03 14:26 by Timo Bingmann at Permlink with 0 Comments. Tags: flex-bison-cpp-example c++ code-example

Released an updated source code package for Flex Bison C++ Example. The example source code is released into the public domain or, at your option, under the Do What The Fuck You Want To Public License (WTFPL).

This bugfix release solves two problems there were reported to me via e-mail:

The first problem were compilation errors that occured when no %union directive is used in the grammar: in this case the include headers order is changed around by bison and thereby breaks compilation. This was fixed by never including parser.h directly, but always using scanner.h.

And the second issue was raised because new versions of flex were released after years of stagnation. The new flex version 2.5.35 adds a virtual function yywrap() to the yyFlexLexer class. This function is automatically defined in any lexer source file generated by flex. However because I copied FlexLexer.h from an older flex distribution, the function definition throughs a "no yywrap() member function" compiler error. Updating the FlexLexer.h with a conditional declaration of yywrap() hopefully did the trick and now works on all versions. Usually this file should be taken from /usr/include and not from the package. However that will break compilation if flex is not installed, and a self-sufficient compilation package was a primary goal of the example.

For more information and the download package see the Flex Bison C++ Example web page.


Funny Drawing with 'C++' 'FLEX' and a Bison

Published Flex Bison C++ Example 0.1

Posted on 2007-08-20 11:53 by Timo Bingmann at Permlink with 2 Comments. Tags: flex-bison-cpp-example c++ code-example

Released example source code package Flex Bison C++ Example. The example source code is released into the public domain or, at your option, under the Do What The Fuck You Want To Public License (WTFPL).

This example shows how to use both Flex and Bison in C++ mode. This way both lexer and parser code and data is encapsulated into classes. Thus the lexer and parser are fully re-entrant, because all state variables are contained in the class objects. Furthermore multiple different lexer-parser pairs can easily be linked into one binary, because they have different class names and/or are located in a different namespace.

Why Use These Old Tools? Well, they are here to stay and they work well. But most important, the code generated by Flex and Bison requires no compile-time dependencies, because they generate fully autonomous source code. So far I have not found any modern parser generator which outputs independent code. It is even possible to compile the generated source on Windows with Visual C++ 2005.

For more information and the download package see the Flex Bison C++ Example web page.


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