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Passing a pointer

Started by gimp May 17, 2004 at 1:15 AM 2 replies 350+ views

Original Post

May 17, 2004 at 1:15 AM

Sanity Check... void ParseString(const std::string& a_Data, CObject* a_Parent, size_t& a_CurrentOffset) { a_Parent = Something } Once the function exits the pointer passed in, a_Parent loses it''s value. It''s like it''s say an int being passed by val. ... but it''s a pointer. I thought it didn''t matter. Have I lost it? Does it always work like this? Have I just never passed a pointer in to a function before and it always does this? I''m a bit embarresed even asking this...

SiCrane

Mod

473

SiCrane

May 17, 2004 at 1:26 AM

You passed a pointer by value, if you want the calling function''s CObject * to be modified by your ParseString() function, either pass the parameter by reference or pointer. i.e. either CObject *& or CObject **.

HFX

May 17, 2004 at 1:30 AM

Yep It will happen every time. The problem is in your function you created data on the stack. When you left the function, that data was deallocated. Since you assigned your data to the pointer, upon leaving, your pointer points to no mans land. A way to solve this is to create a new object on the heap (use new) and delete it later. Also your a_parent needs to be dereferenced unless your assinging a point to it.

gimp

Author

gimp

May 17, 2004 at 1:51 AM

Thanks. Looks like I''ve never done this before. I thought that because a_Parent was being assigned on the heap that the pointer would be valid. Since the point was being passed by ref the address change on the stack insude the function was getting destroyed the callee remained unchanged.

I reordered the functions and use a return value to allow it to pass back up.

Many thanks,

Chris

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