Read all stdin C data

Question

I wrote this little function to read all the data from stdin.

I need to know if this function is compatible with POSIX (I mean that it will work on Unix and Unix-like systems), at least it works on Windows ...

char* getLine()
{
    int i = 0, c;
    char* ptrBuff = NULL;

    while ((c = getchar()) != '\n' && c != EOF)
    {
        if ((ptrBuff = (char*)realloc(ptrBuff, sizeof (char)+i)) != NULL)
            ptrBuff[i++] = c;
        else
        {
            free(ptrBuff);
            return NULL;
        }
    }

    if (ptrBuff != NULL)
        ptrBuff[i] = '\0';

    return ptrBuff;
}

stdin '\n' EOF . , , , Unix Unix- ... . ? stdin, ? , fgets() , , ... , , .

EDIT:

getLine():

char* readLine()
{
    int i = 0, c;
    size_t p4kB = 4096;
    void *nPtr = NULL;
    char *ptrBuff = (char*)malloc(p4kB);

    while ((c = getchar()) != '\n' && c != EOF)
    {
        if (i == p4kB)
        {
            p4kB += 4096;
            if ((nPtr = realloc(ptrBuff, p4kB)) != NULL)
                ptrBuff = (char*)nPtr;
            else
            {
                free(ptrBuff);
                return NULL;
            }
        }
        ptrBuff[i++] = c;
    }

    if (ptrBuff != NULL)
    {
        ptrBuff[i] = '\0';
        ptrBuff = realloc(ptrBuff, strlen(ptrBuff) + 1);
    }

    return ptrBuff;
}

:

char* readLine(). , - , , .

char* readLine()
{
    int c;
    size_t p4kB = 4096, i = 0;
    void *newPtr = NULL;
    char *ptrString = malloc(p4kB * sizeof (char));

    while (ptrString != NULL && (c = getchar()) != '\n' && c != EOF)
    {
        if (i == p4kB * sizeof (char))
        {
            p4kB += 4096;
            if ((newPtr = realloc(ptrString, p4kB * sizeof (char))) != NULL)
                ptrString = (char*) newPtr;
            else
            {
                free(ptrString);
                return NULL;
            }
        }
        ptrString[i++] = c;
    }

    if (ptrString != NULL)
    {
        ptrString[i] = '\0';
        ptrString = realloc(ptrString, strlen(ptrString) + 1);
    } 
    else return NULL;

    return ptrString;
}

Answer 1

POSIX: !

getchar(), malloc(), realloc() free(), C , , POSIX. , . , , malloc() stdin.