Question

I’ve made a function that reads a file into the memory in C. But I’m having an issue with the code, random characters seem to appear at the end of the string. Even after I added ‘\0’ at the end. I don’t understand this at all since the whole file appears and I haven’t malloc’d enough room for more characters, so there should be some kind of error if there are more chars? Anyway does anyone knows what’s causing this?

char* LoadSourceFile(char* filename)
{
    int fileSize;
    char* buffer;
    struct stat handle;
    FILE* bestand;

    stat(filename, &handle);
    if (fopen_s(&bestand, filename, "r") != 0) {
        return NULL;
    }

    fileSize = handle.st_size;
    handle.st_size++;
    buffer = (char*)malloc(handle.st_size);
    if (buffer == NULL) {
        return buffer;
    }

    fread_s(buffer, handle.st_size, fileSize, 1, bestand);
    buffer[fileSize] = '\0';
    fclose(bestand);

    return buffer;
}

Answer 1

Look at the return from fread_s which is the number of bytes read to buffer. It could be less than expected.

bytes_read = fread_s(buffer, handle.st_size, fileSize, 1, bestand);
buffer[bytes_read] = '\0';

Edit: you would have to swap the count/size parameters to make what I said correct:

bytes_read = fread_s(buffer, handle.st_size, 1, fileSize, bestand);
buffer[bytes_read] = '\0';