Entering any code that outputs causes a crash

[MineRobber9000]

Any code that isn't supposed to output outputs a gender symbol.

[MineRobber9000]

Erroneous code probably in bf.c

[kitlith]

https://github.com/MineRobber9000/bf3ds/blob/master/src/bf.c#L29

strcat concatinates a string to another string, not a character to a string. Moreover, I believe the behavior is supposed to be that you print each character as they arrive, so that you can print a dialog requesting something for input, and then request input... As it stands it'll only print output when it returns.

I'd reccomend using putchar(*ptr), or, if you want it to be usable for other, more fancy outputs, define a custom function that takes a char and make the user define it elsewhere.

EDIT 2: Even bigger issue, even if strcat worked how you thought it did... you are not initializing output. Which means you're pointing to random memory and writing to it. Oooooops.

Finally, unrelated to the actual issue, I feel this would be better served by a switch statement with a default clause that does nothing. Up to you, of course.

EDIT: You are also not initializing the tape to 0, so there might be any junk there.

[MineRobber9000]

Answering your questions and remarks:

strcat concatinates a string to another string, not a character to a string.

You are also not initializing the tape to 0, so there might be any junk there.

I didn't catch these, thanks.

Even bigger issue, even if strcat worked how you thought it did... you are not initializing output. Which means you're pointing to random memory and writing to it. Oooooops.

https://github.com/MineRobber9000/bf3ds/blob/master/src/bf.c#L11

Maybe I should change char * output to char output[4096]?

[kitlith]

https://github.com/MineRobber9000/bf3ds/blob/master/src/bf.c#L11

Even bigger issue, even if strcat worked how you thought it did... you are not initializing output. Which means you're pointing to random memory and writing to it. Oooooops.

char * output;

This does not initialize output. It declares it, and allocates a 4 byte vaule on the stack.
It's a pointer, which is currently whatever garbage was previously on stack.
You need to initialize the pointer to a useful memory location, for example, via allocation.
Something like char *output = malloc(4096); memset(output, 0, 4096);
You would then free it after use.

Maybe I should change char * output to char output[4096]?
Ah, but then the output buffer is allocated on the stack, and when you return, you return a pointer to something that ends up being deallocated... thus once again leading to undefined behavior.

Once again, I do not reccomend returning the output.
If you want to do so for some other reason, also print each character somehow as they come along. This way, when you implement input, you can have dialogs that ask for input... that aren't printed way too late.

[MineRobber9000]

I'm not implementing input. I thought it over when I began the project and decided it just isn't worth it. I would have to implement a touchscreen keyboard for the input (as you're only allowed to input 1 character) and it would take too much work. Besides, the point of Brainfuck is to be challenging, right? 😃

[kitlith]

Heh. You could queue up input characters. But I see what you're going for, I guess. Good luck.