SPL Compiler

This compiler was created as part of the module Languages and their compilers in Hull University in autumn 2021.
Big thanks to Brian Tompsett and Lydia Bryan-Smith for their help during the semester.

The compiler has been designed to compile the SPL language into C. The language specifications can be find here.

Requirements

⚠️ If you are a Windows or MacOS user: This repository is meant to be used on Ubuntu. It's still possible to run the compiler on Windows but this document doesn't explain how.

• Install Python 3 apt-get install python3.
• Install GCC apt-get install gcc.
• Install Flex apt-get install flex.
• Install Bison apt-get install bison.
• Install GraphViz apt-get install graphviz (we will need it to generate the graphic representation of the parse tree).
• Authorize your user to execute compile.sh chmod u+x compile.sh.
• Having a folder named src_programs and some .spl files in it

How to use and how it works

There are multiple things you can do with this repository, compile.sh regroup all of them so I'll link the associated commands in each section. Each section also contains a diagram to explain what the command does.

Lexer

The lexer can be used to print the tokens of the source program recognized by the compiler.
./compile -m lexer -p <src_program>

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Parser

The parser can be used in debug mode to see the rules used and the stack generated for the source program.
./compile -m parser -p <src_program>

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Tree

The parse tree can be used in 2 differents ways:

1. Printing the JSON format of the tree in the terminal. ./compile -m tree -p <src_program>

ℹ️ If you don't want to use GraphViz: There is an alternative to visualize the tree, you can paste the JSON on https://vanya.jp.net/vtree/

2. Passing the JSON into GraphViz to generate a PNG with a graphical representation of the parse tree. ./compile -m tree -p <src_program> -r

The PNG tree will be created inside the tree_generator/ folder.

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Code

The code feature can also be used in 2 differents ways:

1. Printing the generated code in the terminal. ./compile -m code -p <src_program>

2. Compiling the generated code with GCC to make sure it doesn't give any errors and run smoothly. ./compile -m code -p <src_program> -r

The target code will be stored as src_program.c in the code_generated folder and their compiled version will be named src_program.out

Additional functionalities

On top of the language specification I defined some behaviors for the compiler.

Code optimization

The compiler does some sort of type optimization, when there is an arithmetic expression containing only integers, the expression is precalculated at compile time.

For example 78 - 5 -> a will be compiled as a = 73;
Also WRITE( (26 - 7) ) will be compiled as printf("%d",19);
It doesn't work with arithmetic expressions containing reals.

Type coercion

• Integers can be assigned to real numbers, it won't give any warning.
• Reals can be assigned to integer but it will give a warning.
• Characters can't be assigned to anything else than character variables.
• Arithmetic can be done between integers and reals.
• Arithmetic can be done between characters, it's manipulate the ASCII values.
• Arithmetic can't be done with characters and another type.

Other sementic checks

• Gives a warning if the program identifiers at the beginning and the end aren't identical.
• Gives a warning if the value assigned to an INTEGER is greater than INT_MAX or less than INT_MIN.
• Gives a warning if the variable has been declared but is used without being initialized.
• Doesn't compile if a variable is used without being declared (also work with the program identifier if it's use for a variable).
• Doesn't compile if a variable is declared twice.
• Doesn't compile if the expression in the for loop aren't integer expressions

Other functionalities

• Rename the variable by adding _r at the end if it's a reserved keyword in C, for example volatile will be renamed volatile_r.