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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.lang.c
Subject: Re: A question regarding C string functions
Date: Thu, 3 Apr 2025 09:29:12 +0200
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On 02/04/2025 20:33, Kaz Kylheku wrote:

> It gets more verbose and indented, but the null treatment is
> consistently there.
> 

In the current working draft for the future standard after C23, it says:

"""
Where an argument declared as size_t n specifies the length of the array 
for a function, n can have the value zero on a call to that function. 
Unless explicitly stated otherwise in the description of a particular 
function in this subclause, pointer arguments on such a call may be null 
pointers. On such a call, a function that locates a character finds no 
occurrence, a function that compares two character sequences returns 
zero, and a function that copies characters copies zero characters.
"""

And the change list includes :

"""
Allowed zero-length operations on null pointers.
"""


That sounds like if you call something like "strncpy" with a maximum 
length of 0, then null pointers are safe - if nothing is moved, copied, 
or searched, then the pointer is not dereferenced and the behaviour is 
defined.

It seems likely to me that this is the behaviour you would get with most 
current implementations of the library functions - but of course that is 
not something to rely on until you are using post-C23 standard tools.