possible undefined use of strchr

[Andrey Vul]

Is use of strchr(const char *s, '\0') undefined as as a short form of
(s + strlen(s)) ?
The problem is that memchr requires strlen, so strchr is the only way
to do uncounted char find. Is there a way to use it so that it returns
the address of the '\0' in s?

 

[Andrey Vul]

Is use of strchr(const char *s, '\0') undefined as as a short form of
(s + strlen(s)) ?
The problem is that memchr requires strlen, so strchr is the only way
to do uncounted char find. Is there a way to use it so that it returns
the address of the '\0' in s?

The point of the question is for an implementation of strpcat()
(similar to mempcpy() ), i.e. to allow strcat() chaining (strcat(strcat
(...),...).

 

[Andrey Vul]

In <[email protected]>,



No, that's fine. The Standard specifically provides for this
possibility:

"The strchr function locates the first occurrence of c (converted to
a char ) in the string pointed to by s .  The terminating null
character is considered to be part of the string."

Oh, strchr returns NULL when the sentinel zero of the string has been
reached _and_ second argument is not zero?

 

[Andrey Vul]

om>> The problem is that memchr requires strlen, so strchr is the only way
om>> to do uncounted char find. Is there a way to use it so that it returns
om>> the address of the '\0' in s?

Surely strlen(s)+1 will find the \0

That returns the index, not the pointer.
strchr(s, '\0') returns the pointer

 

[Keith Thompson]

That returns the index, not the pointer.
strchr(s, '\0') returns the pointer

So does s + strlen(s).