Realloc 2d char array

Question

I have a 2d dynamically allocated char array that is supposed to hold strings from a file (stdin) up to a space character. Since I don't know how many strings are in the file, I'm constantly reallocating bigger chunks of memory for the 2d array so I have enough space to store each individual string. For instance, if I type in "hello world" as input to the program, I expect 'h' to be printed out since hello would be the first string and h would be the first character of that string.

size_t size_buffer = 1;
char* buffer = (char*) malloc(size_buffer * sizeof(char)); //initial allocation that can hold 1 single char
size_t cur_nchars = 0; //number of characters read in current string

size_t size_words = 1; //initially only hold 1 string
char** words = (char**) malloc(size_words * sizeof(char*));
size_t cur_nwords = 0; //number of strings read

char read;
while ((read = getchar()) != EOF && !ferror(stdin)) {   
    if (read == ' ') { //space character
        //printf("reached a space character\n");
        words[cur_nwords] = buffer; //store string into words string array
        cur_nwords++; //increase number of words stored
        if (cur_nwords == size_words) { //maximum size hit
            size_words *= 2; //multiply old size by 2
            char** temp_words = (char**) realloc(words, size_words); //realloc new array twice as big

            if (!temp_words) {
                printf("can't allocate more memory");
                for (size_t i = 0; i < cur_nwords; ++i) {
                    free(words[i]);
                }
                free(words);
                exit(1);
            }
            else
                words = temp_words; //have old point to new
        }
        buffer = NULL;
        buffer = (char*)malloc(sizeof(char));
        cur_nchars = 0;
        continue;
    }
    if (cur_nchars == size_buffer) { //maximum length of string reached
        size_buffer *= 2; //new max length is doubled
        char* temp = realloc(buffer, size_buffer); //reallocate memory
        if (!temp) {
            printf("can't allocate more memory");
            free(buffer);
            exit(1);
        }
        else {
            buffer = temp; //set buffer to point to same location as temp
        }
    }
    buffer[cur_nchars] = read; //store character in char array
    cur_nchars++;   //increase # chars in string
}
printf("%c", words[0][0]); //throws error!

However after the code exits this loop, the contents of the 2d array words seems to be getting wiped for some reason (can't read memory error)...I have a feeling that I'm not reallocating the memory to the 2d array correctly. Do I need to reallocate the char array strings themselves as well when I'm reallocating the 2d array if the length of the strings themselves aren't changing?

You need to provide a [MCVE] including input and desired output. — Jabberwocky, May 04 '18 at 07:46
https://www.programiz.com/c-programming/c-dynamic-memory-allocation — Gerasimos Ragavanis, May 04 '18 at 07:52
See: [Do I cast the result of malloc?](http://stackoverflow.com/q/605845/995714) — David C. Rankin, May 04 '18 at 07:55
`buffer = (char*)malloc(sizeof(char));` I'm worried about this. A buffer of one character — Swift - Friday Pie, May 04 '18 at 07:56
@Swift yeah I could make it larger but I don't think that's the issue because I can print each individual string correctly — Howard Wang, May 04 '18 at 07:59
@Howard Wang at which point? before realloc? I don't see wher you store actual size of buffer. What realloc does is copy of old allocated memory to a new location that was allocated and returned. SO it would copy a single character. I'm still digging into code though. — Swift - Friday Pie, May 04 '18 at 08:02
@AlexanderDmitriev oh yeah my bad, forgot that line of code. It didn't change anything tho — Howard Wang, May 04 '18 at 08:04
One more problem: `realloc (words, size_words)` is not the same as `realloc (words, size_words * sizeof (char*))` — Alexander Dmitriev, May 04 '18 at 08:09
@AlexanderDmitriev yeap, after reallocation words is too small, to contain size_words pointers. AND that's why I hated C's dynamic memory way. ALso, imho this code got too many reallocation, but it's just performance issue — Swift - Friday Pie, May 04 '18 at 08:12
Next problem: your code will fail if you enter only one word. `words` is not zero-initialised. — Alexander Dmitriev, May 04 '18 at 08:14
@AlexanderDmitriev Oh yeah, that was the problem...because I was allocating too few bytes and forgot to multiply that by 8. Thanks! — Howard Wang, May 04 '18 at 08:14
@AlexanderDmitriev Yeah there's a lot of edge cases I still need to cover like what happens to the last word in stdin that gets read because as of right now it won't be stored since there's no space after it — Howard Wang, May 04 '18 at 08:15
What you should *really* do is run it in a debugger and execute it step-by-step, recording `buffer` and `words` on a sheet (or using `printf` with `%p` specifier) and checking, if 'words[0, 1, 2 ... ]` still have the same values — Alexander Dmitriev, May 04 '18 at 08:16
use `iswspace` (wctype.h) ? ANyway, Alexander got right answer, let's book it — Swift - Friday Pie, May 04 '18 at 08:17

Realloc 2d char array

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