...
When called with a pointer to (or array of) const characters, the return value from the following functions shall be treated as a pointer to const characters:
strpbrk(),strchr strchr(), strrchr(), strstr()wcspbrk(),wcschr wcschr(),wcsrchr wcsrchr(), wcsstr()memchr(),wmemchr wmemchr()
Do not attempt to modify a string literal. Use a named array of characters to obtain a modifiable string.
...