A C compiler written in Python
Project description
ShivyC is a dependency-free C compiler written in Python 3, targeting Linux x86-64 machines. ShivyC seeks to eventually support the entire C11 standard and produce reasonably efficient code. For ShivyC’s current feature set, see the test files in the tests/general_tests and tests/feature_tests directories.
ShivyC is a rewrite from scratch of my older attempt at a C compiler, ShivC, with much more emphasis on feature completeness and code quality. See the ShivC README for more details on the target improvements.
Quickstart
For compilation of C code, ShivyC only requires Python 3. Assembling and linking are done using the GNU binutils and glibc, which you almost certainly already have installed.
To install ShivyC:
pip3 install shivyc
For command line usage info:
shivyc
To create, compile, and run an example program:
printf "%s\n" '#include <stdio.h>' > test.c
printf "%s\n" 'int main() { printf("hello, world!\n"); }' >> test.c
shivyc test.c
./out
To run the tests:
git clone https://github.com/ShivamSarodia/ShivyC.git cd ShivyC python3 -m unittest discover
Implementation Overview
Preprocessor
ShivyC currently has a very limited preprocessor that parses out comments and expands #include directives. These features are implemented between lexer.py and preproc.py. A more complete preprocessor will be implemented.
Lexer
The ShivyC lexer is implemented primarily in lexer.py. Additionally, tokens.py contains definitions of the token classes used in the lexer and token_kinds.py contains instances of recognized keyword and symbol tokens.
Parser
The ShivyC parser uses recursive descent techniques for all parsing. It is implented in parser/*.py and creates a parse tree of nodes defined in tree/nodes.py and tree/expr_nodes.py.
IL generation
ShivyC traverses the parse tree to generate a flat custom IL (intermediate language). The commands for this IL are in il_cmds/*.py. Objects used for IL generation are in il_gen.py, but most of the IL generating code is in the make_code function of each tree node in tree/*.py.
ASM generation
ShivyC sequentially reads the IL commands, converting each into x86-64 assembly code. ShivyC performs register allocation using George and Appel’s iterated register coalescing algorithm; see References below. The general ASM generation functionality is in asm_gen.py, but much of the ASM generating code is in the make_asm function of each IL command in il_cmds/*.py.
Contributing
ShivyC has so far been an entirely individual project. That said, pull requests are welcome if they pass flake8 and are well-tested.
References
C11 Specification - http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
x86_64 ABI - http://web.archive.org/web/20160801075139/http://www.x86-64.org/documentation/abi.pdf
Iterated Register Coalescing (George and Appel) - https://www.cs.purdue.edu/homes/hosking/502/george.pdf
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