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;}

This is awesome.

wow

Eh beh

how te fook. (also who is here from bf in 100 seconds)

5th

@blankettripod me, im here from the video

same here came from the video, understanding brainf better.

How does this even compile in C? It's wrong syntactically.
Please give a refined code of this.

@ShresthaShome can you explain what syntax error you can see?

Also here from the video: https://www.youtube.com/watch?v=hdHjjBS4cs8

@usercybe maybe because of main(a,b){...} which should be void main(int a, char** b){...}. Or s[99] which should contain the type declaration. But when running with gcc:

bf.c:3:1: warning: data definition has no type or storage class
 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
 ^
bf.c:3:1: warning: type defaults to ‘int’ in declaration of ‘s’ [-Wimplicit-int]
bf.c:3:8: warning: type defaults to ‘int’ in declaration of ‘r’ [-Wimplicit-int]
 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
        ^
bf.c:3:13: warning: type defaults to ‘int’ in declaration of ‘d’ [-Wimplicit-int]
 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
             ^
bf.c:3:15: warning: type defaults to ‘int’ in declaration of ‘c’ [-Wimplicit-int]
 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
               ^
bf.c:3:17: warning: return type defaults to ‘int’ [-Wimplicit-int]
 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
                 ^~~~
bf.c: In function ‘main’:
bf.c:3:17: warning: type of ‘a’ defaults to ‘int’ [-Wimplicit-int]
bf.c:3:17: warning: type of ‘b’ defaults to ‘int’ [-Wimplicit-int]
bf.c:3:37: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
 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
                                     ^
bf.c:3:34: warning: initialization makes pointer from integer without a cast [-Wint-conversion]
 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
                                  ^
bf.c:4:18: warning: pointer/integer type mismatch in conditional expression
    ?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;}
                  ^
bf.c:4:28: warning: implicit declaration of function ‘syscall’ [-Wimplicit-function-declaration]
    ?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;}
                            ^~~~~~~
bf.c:4:27: warning: pointer/integer type mismatch in conditional expression
    ?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;}
                           ^
bf.c:4:50: warning: pointer/integer type mismatch in conditional expression
    ?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;}
                                                  ^
bf.c:3:68: warning: assignment makes integer from pointer without a cast [-Wint-conversion]
 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
                                                                    ^
bf.c:4:64: warning: assignment from incompatible pointer type [-Wincompatible-pointer-types]
    ?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;}
                                                                ^
bf.c:4:80: warning: assignment from incompatible pointer type [-Wincompatible-pointer-types]
    ?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;}

It's all just warnings. It does compiles in the end.

how do i compile with it???

how to compile some bf

@tpglitch you compile the program with GCC
gcc -o bf bf.c
Then you pass the program as an argument
./bf +++++,.--

main is recursive wow

r e c u r s e m a i n

using gcc to compile results in a binary that segfaults on any input

Same here, it does compile, but it always segfaults.

$ /bin/gcc --version | head -n1
gcc (GCC) 12.2.1 20230201

$ expac '%v' gcc
12.2.1-2

$ expac -Ss '%r-%v' '^gcc$'
core-12.2.1-2

Still nice idea, but for some reason just doesn't work.

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.