Your answer is in this paragraph of FAQ: https://docs.codewars.com/training/troubleshooting#c-c-signal-11---sigsegv

It's not exactly your solution segfaulting, but it causes tests to crash.

seeing as p points to the beginning of text

But it doesn't. That code is inside the condition if (*p == ' ' || *p == '\0')

Shouldn't p point to the end of each word

Yes. p is the space or null terminator, so that p-1 is the last char of the previous word.