c - Sprintf Segmentation Fault

Question

numCheck is number between 1-1000. This code gives me a segfault only when I collect the results of sprintf in charcheck. If I simply use sprintf without using the results, I don't get a seg fault. What's happening here?

char * numString;
int charcheck = sprintf(numString, "%d", numCheck);

Answer 1

You need to provide your own memory for sprintf. Also, don't use sprintf, but rather snprintf:

char buf[1000] = {0};

snprintf(buf, 999, ....);

Alternatively you can allocate memory dynamically:

char * buf = new char[BUFSIZE];
snprintf(buf, BUFSIZE-1, ...);
/* ... */
delete[] buf;