kabsa

A compiler built using Bison & Flex C++ interfaces that generates code for a hypothetical stack-based machine

Table of Contents

• About the Project
  • Example Test Cases
    • if-else statements
    • Loops
    • Expressions
    • Functions
    • Enums
    • Enums Error
    • Semantic Errors
    • Syntax Errors
  • Output Quadruples
  • Future Plans
  • Built With
• Getting Started
  • Prerequisites
  • Running
• Acknowledgements

About The Project

Instead of using Bison and Flex C interfaces, or even use the C interfaces and compile them using a C++ compiler, this compiler was built using both Bison and Flex C++ interfaces.

Example Test Cases

if-else statements

if.kabsa:

function main() {
  x = 10;
  b;
  if (x == 10) {
    b = 10;
  } else if (x == 5) {
    b = 5;
  } else {
    b = x;
  }
}

if.asm:

	PROC	main
	PUSH	10
	POP     x
	PUSH	b
	PUSH	x
	PUSH	10
	CMPEQ
	JNZ	L0000
	PUSH	10
	POP     b
	JMP	L0001
L0000:
	PUSH	x
	PUSH	5
	CMPEQ
	JNZ	L0002
	PUSH	5
	POP     b
	JMP	L0003
L0002:
	PUSH	x
	POP     b
L0003:
L0001:
	ENDP	main

Symbol Table:

Variable	Type	Initialized
main	function	1
b	variable	1
x	variable	1

---

Loops

loops.kabsa:

function main() {
  for (i = 0; i < 10; i = i + 1) {
    b = 10;
  }

  x = 0;

  while (x < 20) {
    x = x + 1;
  }

  x = 0;

  do {
    x = x + 1;
  } while (x < 20);

  switch (x) {
    case 1:
      x = 10;
      break;

    default:
      break;
  }
}

loops.asm:

	PROC	main
	PUSH	0
	POP     i
L0000:
	PUSH	i
	PUSH	10
	CMPLT
	JNZ	L0001
	PUSH	10
	POP     b
	PUSH	i
	PUSH	1
	ADD
	POP     i
	JMP	L0000
L0001:
	PUSH	0
	POP     x
L0002:
	PUSH	x
	PUSH	20
	CMPLT
	JNZ	L0003
	PUSH	x
	PUSH	1
	ADD
	POP     x
	JMP	L0002
L0003:
	PUSH	0
	POP     x
L0004:
	PUSH	x
	PUSH	1
	ADD
	POP     x
	PUSH	x
	PUSH	20
	CMPLT
	JZ	L0004
	PUSH	x
	PUSH	1
	CMPEQ
	JZ	L0005
	JMP	L0006
L0005:
	PUSH	10
	POP     x
	JMP	L0007
L0006:
	JMP	L0007
L0007:
	ENDP	main

Symbol Table:

Variable	Type	Initialized
main	function	1
x	variable	1
b	variable	1
i	variable	1

---

Expressions

expressions.kabsa:

function main() {
  x = 0;
  y = 10;
  z = x / y - x;
  a = true;
  b = false;
  c = a & b;
}

expressions.asm:

	PROC	main
	PUSH	0
	POP     x
	PUSH	10
	POP     y
	PUSH	x
	PUSH	y
	DIV
	PUSH	x
	SUB
	POP     z
	PUSH	1
	POP     a
	PUSH	0
	POP     b
	PUSH	a
	PUSH	b
	AND
	POP     c
	ENDP	main

Symbol Table:

Variable	Type	Initialized
c	variable	1
b	variable	1
a	variable	1
main	function	1
z	variable	1
y	variable	1
x	variable	1

---

Functions

function.kabsa:

function sum(x, y) {
  return x + y;
}

function main() {
  a = sum(10, 20);
  a = sum(a, a);
}

function.asm:

	PROC	sum
	POP     x
	POP     y
	POP     x
	POP     y
	ADD
	RET
	ENDP	sum
	PROC	main
	PUSH	20
	PUSH	10
	CALL	sum
	POP     a
	PUSH	a
	PUSH	a
	CALL	sum
	POP     a
	ENDP	main

Symbol Table:

Variable	Type	Initialized
main	function	1
a	variable	1
sum	function	1
y	variable	1
x	variable	1

---

Enums

enums.kabsa:

function main()
{
  enum day_of_the_week
  {
    Mon,
    Sun
  };
  x = Mon;
}

enums.asm:

	PROC	main
	PUSH	0
	POP     Mon
	PUSH	1
	POP     Sun
	PUSH	Mon
	POP     x
	ENDP	main

Symbol Table:

Variable	Type	Initialized
main	function	1
x	variable	1
day_of_the_week	enumerator specifier	1
Sun	enumerator	1
Mon	enumerator	1

---

Enums Error

enums-error.kabsa:

function main()
{
  enum day_of_the_week
  {
    Mon,
    Sun
  };
  x = Tue;
}

Error Message:

8.11: Undeclared variable used

---

Semantic Errors

semantic-error.kabsa:

function main() {
  const x = 10;
  a = 9;
  x = a;
}

Error Message:

5.9: Cannot reassign value to constant variable

---

Syntax Errors

syntax-error.kabsa:

function main()
{
  2s = 10;
}

Error Message:

3.4: syntax error, unexpected INTEGER

---

Output Quadruples

Quadruple	Description
PUSH X	Pushes X to stack
POP X	Pop the top stack value into X
CMPLT	Pops two values from the stack and sets the Z flag to 1 if the older value in the stack is less than the newer value
CMPLE	Pops two values from the stack and sets the Z flag to 1 if the older value in the stack is less or equals than the newer value
CMPNE	Pops two values from the stack and sets the Z flag to 1 if they are not equal
CMPGT	Pops two values from the stack and sets the Z flag to 1 if the older value in the stack is greater than the newer value
CMPGE	Pops two values from the stack and sets the Z flag to 1 if the older value in the stack is greater than or equals the newer value
CMPEQ	Pops two values from the stack and sets the Z flag to 1 if they are equal
ADD	Pops two value from the stack and pushes their summation onto the stack
SUB	Pops two value from the stack and pushes their subtraction onto the stack
MUL	Pops two value from the stack and pushes their multiplication onto the stack
DIV	Pops two value from the stack and pushes their division onto the stack
NEG	Pops a value from the stack and pushes its negation onto the stack
AND	Pops two value from the stack (and them) and pushes the result onto the stack
OR	Pops two value from the stack (or them) and pushes the result onto the stack
NOT	Pops a value from the stack (not it) and pushes the result onto the stack
JMP LABEL	Unconditional jump to LABEL
JNZ LABEL	Jump if zero flag == 0
JZ LABEL	Jump if zero flag == 1
PROC PROC_NAME	Starts procedure/function with name PROC_NAME definition
ENDP PROC_NAME	End procedure/function with name PROC_NAME definition
CALL PROC_NAME	Calls procedure/function with name PROC_NAME, if there are arguments for this function they are pushed into stack first
RET	Return from function call to execute the next line of the code, if the function returns value then it is pop from the tack

Future Plans

• Rigorously test nested and combined code structures
• Modify the Lexer to scan arabic patters
• Implement symbol tables for different scopes
• Scan and parse more code artifacts (e.g comments, classes, etc.)

Built With

• Cygwin g++ compiler
• winflexbison
• Python 3.9 (including Tkinter for GUI)

Getting Started

Prerequisites

• Setup Python using this link
• Download winflexbison and extract the zipped file content straight into the C drive so you’d end up with a directory similar to the following directory C:\win_flex_bison-*.*.*
• Setup Cygwin g++ compiler
• Add C:\win_flex_bison-*.*.* and C:\cygwin64\bin to your environment variables system path

Running

• Run the following commands to compile a compiler executable:

  • win_bison -d parser.yy

  • win_flex scanner.l

  • g++ -I C:\win_flex_bison-2.5.24 main.cc driver.cc lex.kabsa.cc parser.tab.cc

    Where win_flex_bison-2.5.24 is the name of the winflexbison directory in the C drive

• Run the following command to compile a .kabsa code file:

  .\a.exe "<input file path>" "<output directory>"

  • Example:

    .\a.exe "D:/examples/if.kabsa" "D:/examples_output"

  Where a.exe is kabsa compiler executable output from the g++ compilation command

• To run using the GUI:

  • Copy the compiler executable a.exe to the gui directory and name it compiler.exe
  • Run the GUI using the following command in the /gui directory: python gui.py

Acknowledgements

• sanwade — Flex Bison & Yacc Tutorial (With Code and Example)
• Jonathan Engelsma — Tutorial: programming with lex/yacc
• IBM — Abstract for Programming Tools
• ANSI C Yacc grammar
• jonathan-beard/simple_wc_example
• Base64 File Converter Tkinter Template