C Compiler

A simple compiler for a subset of the C Programming Language. Generates x86 Assembly. Written in C++

Sustem Compatibility: Linux This software was written and tested on Ubuntu/Debian environment. I cannot guarantee full compatilibty with other distros without proper testing.

Output: Assembly Code that targets Intel 8086 Processor (x86 Assembly) Dependencies: Flex, Bison

Usage

1. Clone this repository

2. Run compile.sh in the root. It will prompt you to provide the 'C' file name. This compiles your input file, checks compile errors (lexical/syntax/symantic) which are written in log.txt inside the 'logs' folder. In case of a successful compilation,the generated assembly code can be found in the assembly folder.

3. In order to run the generated assembly, use a *8086 Microprocessor emulator. Example: emu8086

4. Use debug.sh to use gdb debugger for any issues.

Known Issues

• This implementation of compiler uses static allocation and therefore, doesn't support Recursion.

• Does not come with a linker. So does not support include statements

• Support for structs not yet included.

Sample Output

Input C code:

int fact(int n){
    int f,i;
    f = 1;
    for(i=n;i>0;i--){
    f = f * i;
    }
    return f;
}


int main(){

    int n,f;
    n = 6;
    f = fact(n);
    println(f);
    return 0;
}

Generated x86 Assembly

.MODEL SMALL
.STACK 100H
.DATA 
n2 dw ?
factReturnVariable dw ?
i2 dw ?
f2 dw ?
temp0 dw ?
temp1 dw ?
temp2 dw ?
temp3 dw ?
temp4 dw ?
mainReturnVariable dw ?
f4 dw ?
n4 dw ?
temp5 dw ?
temp6 dw ?
temp7 dw ?
.CODE
fact PROC
PUSH AX
PUSH BX 
PUSH CX 
PUSH DX
PUSH n2
MOV temp0,1
MOV AX,temp0
MOV f2,AX
MOV AX,n2
MOV i2,AX
;Loop Begin
Label2:
;$4 code Begin
MOV temp1,0
MOV AX,i2
CMP AX,temp1
JG Label0
MOV temp2,0
JMP Label1
Label0:
MOV temp2,1
Label1:
;$4 code End
MOV AX,temp2
CMP AX,0
JE Label3
;$7 code Begin
MOV AX,f2
MOV BX,i2
MUL BX
MOV temp4, AX
MOV f2,AX
;$5 code Begin
MOV AX,i2
MOV temp3,AX
DEC i2
JMP Label2
Label3:
;Loop END
MOV AX,f2
MOV factReturnVariable,AX
JMP LabelReturnfact
LabelReturnfact:
POP n2
POP DX
POP CX
POP BX
POP AX
ret
fact ENDP
main PROC
    MOV AX,@DATA
MOV DS,AX 
MOV temp5,6
MOV AX,temp5
MOV n4,AX
MOV n2,AX
CALL fact
MOV AX,factReturnVariable
MOV temp6,AX
MOV f4,AX
CALL OUTDEC
MOV temp7,0
MOV AX,temp7
MOV mainReturnVariable,AX
JMP LabelReturnmain
LabelReturnmain:
MOV AH,4CH
INT 21H
outdec proc
push ax
push bx
push cx
push dx
or ax,ax
jge END_IF1
push ax
mov dl,'-'
mov ah,2
int 21h
pop ax
neg ax
END_IF1:
xor cx,cx
mov bx,10d
REPEAT1:
xor dx,dx
div bx
push dx
inc cx
or ax,ax
jne REPEAT1
mov ah,2
PRINT_LOOP:
pop dx
or dl,30h
int 21h
loop PRINT_LOOP
mov dx,13
mov ah,2
int 21h 
mov dx,10
mov ah,2
int 21h
pop dx
pop cx
pop bx
pop ax
ret
outdec endp
END MAIN