Hello guys, C++ is my first programming language I chose to delve into and have just scratched the basics. One thing I recently am confused about is these keywords I mentioned in the title. It would be quite helpful if someone can brief me about them as these terms are used many places and I don't know if they are replacebly same or different.
One time I saw 0 and NULL in srand(time()) and other time I saw a pointer being initialized to nullptr and NULL so I am quite confused as a beginner
#Need help distinguishing between NULL, nullptr and 0
lapis stirrup
rose crystal
NULL is a remnant from C and should not be used in C++
rose crystal
it's basically just a
#define NULL 0
and exists solely for backwards compatibility with C
forest kiln
i know NULL is basically 0 on every compiler but iirc it's is implementation defined?
lapis stirrup
I saw it being used to initialize a pointer for dynamic allocation of memory
rose crystal
in C, it used to serve the purpose of a null pointer constant
but at have nullptr for that
lapis stirrup
but I heard that we should not dereference a nullptr, is that true?
rose crystal
well, what would be the meaning of doing that?
forest kiln
(yes dereferencing a nullptr is undefined behaviour)
lapis stirrup
I see
hazy trail
(random remark that C23 has/will have nullptr so arguably you should stop using NULL in C as well unless you're writing C code that has to be compatible with old C standards, which I guess is fairly common)
forest kiln
keep in mind that you use nullptr's when working with pointers, and when it is not pointing to something, people coming from other languages might believe that NULL/nullptr is the equivalent of null in like js or C#
lapis stirrup
well, what would be the meaning of doing that?
No point but once I saw a nullptr being assigned a value later during dynamic allocation and we printed out the dereferenced one so I was confused
hazy trail
I saw it being used to initialize a pointer for dynamic allocation of memory
formally has to be a "null pointer constant" or whatever the phrasing is
on gcc/g++ it's iirc __null which is a compiler-specific thing
rose crystal
No point but once I saw a nullptr being assigned a value later during dynamic al...
well, then it wasn't a null pointer at the point of dereference
lapis stirrup
well, then it wasn't a null pointer at the point of dereference
Yeah my bad, they used NULL for that
lapis stirrup
formally has to be a "null pointer constant" or whatever the phrasing is
on gcc/...
I see
Thank you guys I think I will close it, its still advanced for me ig