CSCI 439 FINAL PROJECT (C Minus Minus)

cmm.exe

The objective of this program is to create a compiler to compile code from a made up language I have dubbed C-- to x86 assembly using lex and yacc for parsing and tokenization as well as C code for translation, symbol table and syntax tree building.

Technologies

Languages

C
BASH (makefile)
LEX (tokenizer)
YACC (parsing)

C LIBRARIES

<stdio.h> <string.h> <stdlib.h> <ctype.h> "y.tab.h" "lex.yy.c"

FILES

lexer.lex parser.yacc makefile

ProjectProposal.pdf README

Test files

testprog.txt (test program to be compiled when make-run is entered) testloop.txt (simple loop test) testsbad/badprog1 (undeclared variable test) testsbad/keywordvar (using keyword as variable test) testsbad/multdecl (multiple declaration test)

Build, Installation and Running the executable

1. Type make to build the executible
2. Type make-run to run the executible on testprog.txt
3. Type make clean to clear the executible and associated output file

Making your own programs

1. To build the executible type "make"
2. type ./cmm < "your_program.txt" This will run the CMM compiler on "your_program.txt" and compile your code to x86 assembly, if you want to compile your code with error checking simply type ./cmm < testsbad/"your_program.txt"

Compiler Tests

1. To build the executible type "make"
2. type ./cmm < testsbad/... This will run the compiler on programs with syntax/logical errors from the "testsbad" directory. These programs demonstrate the error handling capabilities of the compiler.

Testing

Sample Code Used

Symbol Table Generated

X86 Assembly Generated

section .text global_start section .data x DQ 9 msg0 DQ "test1", 0 len0 equ $ - abc msg1 DQ "test2", 0 len1 equ $ - xyz section .text

_start: mov edx,len0 mov dx,msg0 mov ebx,1 mov dx,4 int 0x80 mov ecx, 0 ;store loop index var on stack jmp loop0 loop0: push ecx ;save loop index on stack mov ecx, y ;store string to print in ecx int 0x80 ;print value stored in ecx mov edx,len1 mov dx,msg1 mov ebx,1 mov dx,4 int 0x80 mov ax, y ;store if LHS COND var in reg mov bx, 5 ;store if RHS cond var in reg cmp ax, bx ;compare if stmt conditions jg ifstmt0 ;jump if greater than ifstmt1: ifstmt start label mov ecx, "y is > 5" ;store string to print in ecx int 0x80 ;print value stored in ecx pop ecx ;get loop index add ecx, 1 cmp ecx, 10 jl loop0 mov ecx, y ;store string to print in ecx int 0x80 ;print value stored in ecx mov ax, y ;store if LHS COND var in reg mov bx, 5 ;store if RHS cond var in reg mov ecx, abc ;store string to print in ecx int 0x80 ;print value stored in ecx mov ecx, abc ;store string to print in ecx int 0x80 ;print value stored in ecx mov ecx, xyz ;store string to print in ecx int 0x80 ;print value stored in ecx mov ecx, abc ;store string to print in ecx int 0x80 ;print value stored in ecx int 0x80 ;END PROGRAM CALLS mov ebx,0 mov eax,1 int 0x80

Known Issues and Bugs

Currently the only error checking that is working is checking for undeclared variables. Using a keyword as a variable name results in error as expected but the error is being generated by the lexer rule for unrecognized input instead of a custom rule.

I was having trouble finding good documentation on x86 scanning so currently scan statements are unimplemented. BOOL types are untested and code generation for bool types are currently not implemented.

There is also an issue with the parsing as statements in scope of a for loop or if statement are generated twice in assembly and sometimes with the wrong label number. I will either need to add an element to each tree node to keep track of the current scope and change my generate code functions to generate based on scope, Or make separate code generation functions for statements within the loop and if statement scope and general code block statements.

Sources

x86 assembly guide and resources https://docs.oracle.com/cd/E19253-01/817-5477/817-5477.pdf https://en.wikibooks.org/wiki/X86_Assembly/Interfacing_with_Linux https://montcs.bloomu.edu/Information/LowLevel/Assembly/hello-asm.html