pl0c

My attempt at writing a compiler for the PL/0 programming language by Niklaus Wirth.
Initially, the aim was to write the entire compiler from scratch. While working on it, the focus slowly shifted to writing an LLVM frontend.
See GRAMMAR.md for details on the language spec.

Brief implementation details

• Recursive descent parser returns AST
• AST implemented with nodes having a list of nodes as children (CLRS 10.4)
• Symbol table is an unordered linked list
• I/O uses wrapper functions written in C. This makes it easier than handling variadic functions (which now clang can handle for us). These wrappers are implemented in examples/io.c

Building

$ make

Usage

$ ./pl0c <file_name>.pl0

• pl0c outputs a .ll file containing LLVM IR corresponding to the source.
  
• Use llc to get an object file and clang to get an executable.
• If the source uses print and/or scan statements, you'll need compile io.c and link with it.
  io.c contains wrappers with the following signatures:

void print64(int64_t)
int64_t scan64()

examples/build.sh automates all of this. Usage described below.

# get corresponding exectable named <filename>
$ ./build.sh <filename>.pl0

# get executable along with <filename>.ll containing LLVM IR
$ ./build.sh -emit-llvm <filename>.pl0   

Demo : running examples

$ make
$ cd examples
$ ./build.sh -emit-llvm fibonacci.pl0  # get executable named fibonacci and fibonacci.ll (contains IR)
$ ./fibonacci
10
55
$
$ ./build.sh natural_recurse.pl0  # get executable named natural_recurse
$ ./natural_recurse
5
1
2
3
4
5
$

License

All pl0c source code is licensed under the terms of the MIT License.