Thread: pointer_default

Hello everyone,


Could anyone show me the usage of pointer_default please (sample of when we need to use ref, unique and ptr)? After some search, I found too little materials on this topic. :-)


thanks in advance,
George

Any good book on C/C++ should provide enough resources to explain and provide examples of pointer usage. There are also tutorials on line (Google them) that should provide enough sources to answer any questions you may have.

Thanks kcpilot and dwks,


I have found some good link by your advice, and get some further confusions,

Confused about two sentences,

1. "Does not cause aliasing. Storage pointed to by a reference pointer cannot be reached from any other name in the function." from,

http://msdn2.microsoft.com/en-us/lib...53(VS.85).aspx

2. "Does not cause aliasing. Like storage pointed to by a reference pointer, storage pointed to by a unique pointer cannot be reached from any other name in the function." from,

http://msdn2.microsoft.com/en-us/lib...94(VS.85).aspx

What do they mean?


regards,
George

Originally Posted by dwks

pointer_default isn't something to do with pointers. MSDN seems to indicate that it's an attribute, like __c_decl etc.

I have no idea how to use it, though perhaps you can find some information on MSDN. http://msdn2.microsoft.com/en-us/lib...41(VS.85).aspx

Thanks Mats,


I think the concept of non-aliaing could be understood in the two rules,

1. No other pointers could be pointed to the same memory storage;
2. The pointer could be pointed to other storage, i.e. not const pointer.

Right?

About (2), I think it means other pointer has the chance to point to the same storage area if the pointer is pointed to other storage area.

Here is a sample code,

Code:

char* ptr1 = NULL;
char* ptr2 = NULL;
char array[] = "Hello World \n";
ptr1 = array; // allow
ptr2 = ptr1; // not allow
ptr2 = array; // not allow

ptr1 = NULL;
ptr2 = array; // allow;
ptr2 = ptr1; // allow? alias to NULL allowed?

Originally Posted by matsp

I think I explained the "can not alias" points in the unique post. Please ask there if you need clarification, as aliasing is the key, and default_pointer is just one of several pointer types that are defined to be nonaliased.

--
Mats

regards,
George

Thanks Mats,


So you agree with my code/analysis in #6 is correct? :-)

Originally Posted by matsp

Yes, NULL is allowed as an alias, as it can't be accessed - and aliasing is only really a problem where you have two pointers that you are accessing.

--
Mats

regards,
George

Thanks Mats,


Cool!

Originally Posted by matsp

Yes, I agree with that.

--
Mats

regards,
George