Thread: If you declare a local pointer with the same name & type as a pointer data member ...

Originally Posted by deoren

Just to make sure I have this right, the reason this is okay to do is because we're not losing track of any dynamically assigned memory. instead we're just passing the address around to a pointer that we know will free the memory later (class data member with destructor written to explicitly delete it)?

You got the plot.

Couldn't I could have left off the this-> portion as long as I didn't create another local plist variable? Something about an implicit this-> being used?

To be clear, "this->plist" is an unambigious way to write down the class member plist and do something with it. In most situations, omitting "this->" is your prerogative, but you introduced a local variable named plist in some function. That means that "plist" now refers to the local variable instead of the class member. It is a FAR better practice to make sure that class members have descriptive and unique names. I sometimes prefix "my", or a leading underscore (which can be troublesome, since the standard reserves all names _^ where ^ is a capital), but you can really use any little thing.

Originally Posted by Elysia

subfixing

The word is suffix.

Thanks for the great replies!

Originally Posted by deoren

Should the temporary pointer be explicitly deleted instead of relying on the end of the function call to remove it?

To answer that question, no, you should not do that. When I did so (cstack.cpp, r18) I was thinking of getting rid of the variable itself, but instead I was freeing up the memory I had just purposely reserved for the updated array (and now assigned to this->plist). My best guess is that I should allow the tmp_stack pointer to pass out of scope and be removed like an ordinary local variable (cstack.cpp, r19).

Originally Posted by Elysia

Yes, you can do that. So long as you do not create a new variable with an identical name to one stored as a class member, you do not need "this->". It is implicitly deduced by the compiler.
If you do shadow a member variable, then you do need "this->" to distinguish between the two variables. If you omit it, the local variable will be used instead.
Many programmers actually tend to prefer prefixing or subfixing (is that a word?) member variables to distinguish them from local ones. I always tend to add "m_" to all member variables.

Good tip. I've seen the m_ prefix used quite a bit in the book I'm going through, and as my mistake has shown me, there is evidently a really good reason for doing so.

Originally Posted by whiteflags

You got the plot.

Awesome, thanks for the confirmation.

Originally Posted by deoren

To answer that question, no, you should not do that. When I did so (cstack.cpp, r18) I was thinking of getting rid of the variable itself, but instead I was freeing up the memory I had just purposely reserved for the updated array (and now assigned to this->plist). My best guess is that I should allow the tmp_stack pointer to pass out of scope and be removed like an ordinary local variable (cstack.cpp, r19).

Obviously you mustn't because you've just assigned tmp_stack to plist. So if you delete tmp_stack, plist will point to invalid memory now.
The right thing was done in (18), which deletes the old memory only and leaves the new intact.
Once again, you don't have to worry about this if you use smart pointers. I urge you to get familiar with them.