Question

Why does the following segfault?

I am using standard c99, icc compiler with unix. I can’t get this to not segfault, and I am curious why. I am not familiar with strcat/strcpy very much.

char *first = "First";
char *second = "Second";
char *both = (char *)malloc(strlen(first) + strlen(second) + 2);

strcpy(both, first);
strcat(both, " ");
strcat(both, second);

sprintf("%s %s", first, second);

Answer 1

sprintf("%s %s", first, second);

The first parameter of sprintf is a destination buffer. You have given it a constant string as a destination buffer.

If you’re just trying to print out something, did you mean printf?

Otherwise, correct use would be something like:

// declaration of "dest" left as exercise for the reader
//
sprintf(dest, "%s %s", first, second);

Although, sprintf has been superseded by snprintf, which is better to avoid buffer overflows.