Brainfuck interpreter in C

bf.c

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

const int MEMSIZE = 30000;

void run_bf(FILE *fptr) {
    char cmd;
    int mempos = 0, filepos = -1;
    u_char *memory = calloc(MEMSIZE, sizeof(unsigned char));
    int *jump_stack = calloc(MEMSIZE, sizeof(int));
    int skip_cycle = 0;

    if (!memory || !jump_stack) {
        printf("Failed to allocate memory\n");
        exit(1);
    }

    while (++filepos, (cmd = fgetc(fptr)) != EOF) {
        if (skip_cycle) switch(cmd) {
            case '[':
                ++skip_cycle;
                break;

            case ']':
                --skip_cycle;
                break;
            
            default:
                break;
        }
        else switch (cmd) {
            case '>':
                mempos = (mempos + 1) % MEMSIZE;
                break;

            case '<':
                mempos = (mempos - 1 + MEMSIZE) % MEMSIZE;
                break;

            case '+':
                ++memory[mempos];
                break;

            case '-':
                --memory[mempos];
                break;

            case '.':
                printf("%c", memory[mempos]);
                break;

            case ',':
                memory[mempos] = fgetc(stdin);
                break;

            case '[':
                if (memory[mempos]) *jump_stack++ = filepos;
                else ++skip_cycle;
                break;

            case ']':
                --jump_stack;
                if (memory[mempos]) {
                    filepos = *jump_stack - 1;
                    fseek(fptr, filepos + 1, SEEK_SET);
                }
                break;

            default:
                break;
        }
    }

    free(memory);
    free(jump_stack);
}

int main(int argc, char **argv) {
    if (argc == 1) {
        printf("Usage: bf <file.bf>\n");
        exit(1);
    }

    FILE *fptr = fopen(argv[1], "r");

    if (fptr == NULL) {
        printf("Can't access file %s\n", argv[1]);
        exit(1);
    }

    run_bf(fptr);

    fclose(fptr);
    return 0;
}

fib.bf

>++++++++++>+>+[
    [+++++[>++++++++<-]>.<++++++[>--------<-]+<<<]>.>>[
        [-]<[>+<-]>>[<<+>+>-]<[>+<-[>+<-[>+<-[>+<-[>+<-[>+<-
            [>+<-[>+<-[>+<-[>[-]>+>+<<<-[>+<-]]]]]]]]]]]+>>>
    ]<<<
]
This program doesn't terminate; you will have to kill it.
Daniel B Cristofani (cristofdathevanetdotcom)
http://www.hevanet.com/cristofd/brainfuck/

helloworld.bf

 ++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++
 .>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.
 ------.--------.>+.>.

squares100.bf

[squares2.b -- compute square numbers
(c) 2016 Daniel B. Cristofani
http://brainfuck.org/]

>>>>>>>>>>+>++<[
    [[<<+>+>-]++++++[<++++++++>-]<-.[-]<<<]
    ++++++++++.[-]>>>>>[>>>>]<<<<[[<<<+>+>>-]<<<-<]>>++[
        [
            <<<++++++++++[>>>[->>+<]>[<]<<<<-]
            >>>[>>[-]>>+<<<<[>>+<<-]]>>>>
        ]<<-[+>>>>]+[<<<<]>
    ]>>>[>>>>]<<<<-<<+<<
]

This program outputs square numbers. It doesn't terminate.