This is an example reentrant lex/bison parser creating an abstract syntax tree. Most of the problems while building this were related to the weird documentation of lex and bison (all that legacy stuff ...).
This is working in a sense that it might well be suitable as a blueprint for starting such endeavours. Please send me a note if you find a major problem with this.
Disclaimer: I haven't done a lot of C/C++ in the last recent years, so this most probably has lots of non idiomatic stuff in it.
This could be used as syntax tree for integration with an LLVM backend, for example. I didn't follow this path as learning everything necessary about LLVM is not something I currently want to do.
I tried, but C++ support in lex/bison is pretty rough. I failed to properly use the variants stuff they integrated. I looked into boost/spirit when having trouble with this but compilation times of more than 10 seconds for a minimal example is nothing I want to handle any more.
And C++ anyway. I remember so many pitfalls from back in the day when I used this language, that I fear every single step leading to disaster.
The provided Makefile relies on llvm, flex and bison being installed. The following will compile and run the code:
make
./run
There is an additional target for running this through valgrind (use make mem) which helps to find memory leaks.
Please note this requires bison version 3.0.2 at least (this introduced the union stuff). But there is a bug (fixed in version 3.0.3) that will create duplicate type entries in the parser's header file. Let the compiler guide you in which entries to delete. This is a dirty workaround, but sufficient.
There are many resources to be taken into account:
- http://www.gnu.org/software/bison/manual
- http://epaperpress.com/lexandyacc/index.html
- http://gnuu.org/2009/09/18/writing-your-own-toy-compiler/
Mostly missing is location tracking (which line/column did an error occur?). This should be easily possible using other examples on the net.
Copyright (c) 2015, Gereon Frey
All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.