A Brainfuck interpreter written in C

BrainfuckInterpreter.c

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

#define STACK_MAX 100
#define TAPE_MAX 30000
#define ECHO_MESSAGES 1

enum MESSAGE
{
	TOO_BIG, TOO_SMALL, OUT_OF_BOUNDS, STACK_OVERFLOW, TOO_MANY_LOOPS_CLOSED, NOT_ENOUGH_LOOPS_CLOSED, UNKNOWN_SYMBOL
};

typedef enum MESSAGE MESSAGE;

void interpret(unsigned char* program);
void message(MESSAGE message, unsigned int symbol);

int main()
{
	unsigned char *program = malloc(0), *temp;
	char c;

	unsigned int i;

	for(i = 0;;i++)
	{
		c = getchar();
		if(c == '\n')
			break;
		program[i] = c;
		temp = realloc(program, (i+1)*sizeof(unsigned char*));
		program = temp;
	}
	interpret(program);
	free(program);
	return 0;
}

void interpret(unsigned char* program)
{
	unsigned char tape[TAPE_MAX] = {0}, stack[STACK_MAX];
	unsigned char* ptr = tape;

	int stackTop = -1;

	unsigned int i;

	for(i = 0; i < strlen(program); i++)
	{
		switch(program[i])
		{
			case '+':
				if(*ptr < UCHAR_MAX)
					++*ptr;
				else
				{
					message(TOO_BIG, i+1);
					return;
				}
				break;
			case '-':
				if(*ptr > 0)
					--*ptr;
				else
				{
					message(TOO_SMALL, i+1);
					return;
				}
				break;
			case '>':
				if(ptr-tape < TAPE_MAX-1)
					++ptr;
				else
				{
					message(OUT_OF_BOUNDS, i+1);
					return;
				}
				break;
			case '<':
				if(ptr > tape)
					--ptr;
				else
				{
					message(OUT_OF_BOUNDS, i+1);
					return;
				}
				break;
			case '.':
				putchar(*ptr);
				putchar('\n');
				break;
			case ',':
				*ptr = getchar();
				break;
			case '[':
				if(stackTop < STACK_MAX-1)
					stack[++stackTop] = i;
				else
				{
					message(STACK_OVERFLOW, i+1);
					return;
				}
				break;
			case ']':
				if(stackTop > -1)
					if(*ptr)
						i = stack[stackTop];
					else
						stack[stackTop--] = 0;
				else
				{
					message(TOO_MANY_LOOPS_CLOSED, i+1);
					return;
				}
				break;
			default:
				message(UNKNOWN_SYMBOL, i+1);
		}
	}
	if(stackTop != -1)
		message(NOT_ENOUGH_LOOPS_CLOSED, i);
}

void message(MESSAGE message, unsigned int symbol)
{
	if(ECHO_MESSAGES)
		switch(message)
		{
			case TOO_BIG:
				printf("%s%d%s%d\n","ERROR: Cells cannot contain values above ", UCHAR_MAX, ". SYMBOL #", symbol);
				break;
			case TOO_SMALL:
				printf("%s%d\n","ERROR: Cells cannot contain values below zero. SYMBOL #", symbol);
				break;
			case OUT_OF_BOUNDS:
				printf("%s%d\n","ERROR: Out of bounds. SYMBOL #", symbol);
				break;
			case STACK_OVERFLOW:
				printf("%s%d\n","ERROR: Stack overflow. SYMBOL #", symbol);
				break;
			case TOO_MANY_LOOPS_CLOSED:
				printf("%s%d\n","ERROR: Too many closing brackets. SYMBOL #", symbol);
				break;
			case NOT_ENOUGH_LOOPS_CLOSED:
				printf("%s%d\n","ERROR: Not all loops are closed. SYMBOL #", symbol);
				break;
			case UNKNOWN_SYMBOL:
				printf("%s%d\n", "WARNING: Unknown symbol. SYMBOL #", symbol);
		}
}