bf.c

/* The world's smallest Brainfuck interpreter in C, by Kang Seonghoon
 * http://j.mearie.org/post/1181041789/brainfuck-interpreter-in-2-lines-of-c */
s[99],*r=s,*d,c;main(a,b){char*v=1[d=b];for(;c=*v++%93;)for(b=c&2,b=c%7?a&&(c&17
?c&1?(*r+=b-1):(r+=b-1):syscall(4-!b,b,r,1),0):v;b&&c|a**r;v=d)main(!c,&a);d=v;}

My compiled binary with gcc also gets segfaults for any input! Anyone have a tip!?

My GCC: gcc (Ubuntu 12.1.0-2ubuntu1~22.04) 12.1.0

See below

you'll need to refactor the bf compiler so that it's not implicitly typing all untyped variables as ints, this only works as-is on platforms where the int width is the same as a char (1 octet/8 bits), which is the case on the pdp11. To run this as-is, your best bet is to see if you can find an emulator for the pdp11, if it exists.

No it isn't. It does assume that int has the same size as a pointer, which no longer holds in modern 64-bit architectures, but I'm pretty sure that you can still compile and run this code in 32-bit architectures by, for example, using -m32 in GCC to force it. (As you can imagine, because I wrote that code. But I'm on a road and I cannot readily test that, so YMMV.)

How does this work? :O

To any newcomers:

Compile using gcc with the flag "-m32"

You may need to install the gcc-multilib package in order to target an x86 binary

After you have the right libraries installed, you should be able to compile like this:

gcc -m32 -o bf bf.c

good stuff.

Here is the clarified version. I used gpt-4 to reconstruct the code, meaning I just wanted to share the clarified version for learning purposes. I don't know C language, but I was curious.

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

#define TAPE_SIZE 30000

// Declare an array to act as the tape for Brainfuck. Initialize all to zero.
unsigned char s[TAPE_SIZE] = {0};

// This will be the data pointer used in Brainfuck
unsigned char* ptr = s;

// Forward declaration of the main function to make it recursive
int main(int argc, char *argv[]);

int main(int argc, char *argv[]) {
  char* v;

  // Ensure that a Brainfuck program is provided as an argument
  if (argc != 2) {
    fprintf(stderr, "Usage: %s 'brainfuck_code'\n", argv[0]);
    return 1;
  }

  v = argv[1];

  while (*v) {
    switch (*v) {
      case '>':
        ptr++;
        // Boundary check to prevent going beyond the tape
        if (ptr >= s + TAPE_SIZE) {
          fprintf(stderr, "Error: Pointer out of bounds\n");
          return 1;
        }
        break;
      case '<':
        // Boundary check to prevent going before the tape
        if (ptr <= s) {
          fprintf(stderr, "Error: Pointer out of bounds\n");
          return 1;
        }
        ptr--;
        break;
      case '+':
        (*ptr)++;
        break;
      case '-':
        (*ptr)--;
        break;
      case '.':
        putchar(*ptr);
        break;
      case ',':
        *ptr = (unsigned char)getchar();
        break;
      case '[':
        if (!*ptr) {
          int loop = 1;
          while (loop > 0) {
            v++;
            if (*v == '[') loop++;
            if (*v == ']') loop--;
          }
        }
        break;
      case ']':
        if (*ptr) {
          int loop = 1;
          while (loop > 0) {
            v--;
            if (*v == '[') loop--;
            if (*v == ']') loop++;
          }
        }
        break;
    }
    v++;
  }

  return 0;
}

How to compile?

gcc brainfuck.c

How to run?

./a.out "++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.
"

This should dispay

Hello world

Here is the clarified version. I used gpt-4 to reconstruct the code, meaning I just wanted to share the clarified version for learning purposes. I don't know C language, but I was curious.

Honestly looks like chat gpt just spat out a generic bf interpreter, it doesn't share many characteristics with the minimal interpreter.

Here is the clarified version. I used gpt-4 to reconstruct the code, meaning I just wanted to share the clarified version for learning purposes. I don't know C language, but I was curious.

Honestly looks like chat gpt just spat out a generic bf interpreter, it doesn't share many characteristics with the minimal interpreter.

Yeah, it doesn't even call main recursively, it just iterates through the string. For some reason, ChatGPT has been upsetting me more and more recently (

After a few back and forth with GPT-4o, I got this:

#include <unistd.h>  // for syscall

#define MEMORY_SIZE 99
#define SYSCALL_WRITE 4

#define INCREMENT '+'
#define DECREMENT '-'
#define SHIFT_RIGHT '>'
#define SHIFT_LEFT '<'
#define OUTPUT '.'
#define INPUT ','
#define LOOP_START '['
#define LOOP_END ']'

#define IO_OPERATION_FLAG 2

#define TO_CHAR(x) ((char)(x))
#define TO_INT(x) ((int)(x))

char memory[MEMORY_SIZE], *pointer = memory, *return_address, command;

int main(char argument, char **arguments) {
    return_address = arguments;
    char *code = return_address[1];
    
    while ((command = TO_CHAR(*code++)) != '\0') {
        command = TO_CHAR(TO_INT(command) % 93);

        char is_io_operation = TO_CHAR(command & IO_OPERATION_FLAG);
        char is_pointer_operation = TO_CHAR(command % 7);

        if (is_pointer_operation) {
            if (argument) {
                if (command == INCREMENT || command == DECREMENT) {
                    if (command == INCREMENT) {
                        *pointer += INCREMENT - '0';
                    } else {
                        *pointer += DECREMENT + '0';
                    }
                } else if (command == SHIFT_RIGHT || command == SHIFT_LEFT) {
                    if (command == SHIFT_RIGHT) {
                        pointer += SHIFT_RIGHT - '>';
                    } else {
                        pointer += SHIFT_LEFT - '<';
                    }
                } else if (command == OUTPUT || command == INPUT) {
                    syscall(SYSCALL_WRITE - !is_io_operation, is_io_operation, pointer, 1);
                }
            }
        } else {
            code = return_address;  // Set code pointer back to the start of the current command
        }

        while (is_io_operation && (command | argument ** pointer)) {
            code = return_address;
            main(!command, &argument);  // Toggle argument based on the command
        }

        return_address = code;
    }

    return 0;
}

Wow. wow.

To any newcomers:

Compile using gcc with the flag "-m32"

You may need to install the gcc-multilib package in order to target an x86 binary

After you have the right libraries installed, you should be able to compile like this:

gcc -m32 -o bf bf.c

Cheers!

Og code using an online C beautifier: https://codebeautify.org/c-formatter-beautifier/y255f5fa5

s[99], * r = s, * d, c;
main(a, b) {
  char * v = 1[d = b];
  for (; c = * v++ % 93;)
    for (b = c & 2, b = c % 7 ? a && (c & 17 ?
        c & 1 ? ( * r += b - 1) : (r += b - 1) : syscall(4 - !b, b, r, 1), 0) : v; b && c | a ** r; v = d) main(!c, & a);
  d = v;
}