realloc invalid next size whenever I break out of a while loop

Question

I have just started learning C and I've started by doing some projects in this repo, specifically this one. I try not to JUST copy code, but when writing the "readLine" function I ran into something that I just don't see why it's happening or even less so how to fix it.

For context here is the function I wrote:

char *readLine(void){
    int buffsize = shbuffsize;
    char *buffer = malloc(sizeof(char) * buffsize);
    char c;
    int pos = 0;


    if(CheckMallocError(buffer, "buffer")){ // Checking memory allocation fault
        exit(EXIT_FAILURE); 
    }

    while ((c = getchar()) != '\n' || c != EOF) {
        if(pos >= buffsize){ // If we exeed the buffers size it needs to be extended
            buffsize += shbuffsize;
            buffer = realloc(buffer, buffsize);
        }

        buffer[pos] = c;
        pos++;
    }

    printf("exited"); // NEVER GET HERE
    return buffer;    // PROBARBLY NOT HERE EITHER
}

As you see by my comments "exited" never gets printed. However, if I put

printf("%i",pos);

on the line beneath pos++; (still inside the loop) i get correct looking output which to me indicate that that the loop isn't infnite. Example input: "hi" | output: 123.

Then I decided to test adding a break; to be certain that I exit the loop. That is when I got the realloc invalid next size error message. (Compiles fine, the error shows up as soon as i press enter after typing something). For context this is the new code:

char *readLine(void){
    int buffsize = shbuffsize;
    char *buffer = malloc(sizeof(char) * buffsize);
    char c;
    int pos = 0;


    if(CheckMallocError(buffer, "buffer")){ // Checking memory allocation fault
        exit(EXIT_FAILURE); 
    }

    while ((c = getchar()) != '\n' || c != EOF) {
        if(pos >= buffsize){ // If we exeed the buffers size it needs to be extended
            buffsize += shbuffsize;
            buffer = realloc(buffer, buffsize);
        }

        buffer[pos] = c;
        pos++;
        break;
    }

    printf("exited"); // NEVER GET HERE
    return buffer;    // PROBARBLY NOT HERE EITHER
}

Exact message:

realloc(): invalid next size
[1]    1408 abort

The two functions are identicall execept for that one break statement and it doesn't make sense to me why that would break everything. Especially since we shouldn't even have to extend the buffer for only two characters.

You loop condition is wrong. Also note that [`getchar`](https://en.cppreference.com/w/c/io/getchar) returns an **`int`** which is rather important for the comparison against the `int` value `EOF`. — Some programmer dude, Jun 27 '22 at 17:53
And your `printf` debugging is flawed, as the output will *buffered* and not actually written when you call `printf`. Use a [*debugger*](https://stackoverflow.com/questions/25385173/what-is-a-debugger-and-how-can-it-help-me-diagnose-problems) to help you diagnose what's happening. — Some programmer dude, Jun 27 '22 at 17:55
As for a possible reason behind the error: You don't terminate the string. You don't even allocate space for the terminator. — Some programmer dude, Jun 27 '22 at 17:56
At the end of the loop, you want: `buffer[pos] = 0;` to add the string terminator. To make space for that, use: `char *buffer = malloc(buffsize + 1);` and `buffer = realloc(buffer, buffsize + 1);` — Craig Estey, Jun 27 '22 at 18:50

**realloc invalid next size** whenever I break out of a while loop

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realloc invalid next size whenever I break out of a while loop