Re: Desctruction of objects inside a static nested map holding pointers

James Kanze <>
Sat, 24 Nov 2007 09:24:45 -0800 (PST)
On Nov 23, 3:19 pm, wrote:

On Nov 23, 2:04 pm, alan <> wrote:

On Nov 23, 9:55 pm, wrote:> Hello friends,

I have a map like std::map< std::string ,
std::map<std::string, std::string>* >
EpPropCache::propertyCache ; (This is a static instance
and taken from *.cpp file)

As you can see the value is a pointer to another map. I do
new of std::map<std::string, std::string> and add the
pointer to the map.

Do I have to delete the map objects which I create with
new , which I store on the static map instance?


Alternatively, use boost::shared_ptr<std::map<std::string,
std::string> >, which will automatically release them. Just make sure
that, except for initializing a shared_ptr (and initializing only from
a new), you do not, ever, assign a shared_ptr from a plain old
pointer. shared_ptr to shared_ptr is what you should always do. Also
avoid getting a plain pointer from a shared_ptr, because it raises the
question for later programmers - should the plain pointer be deleted
or no?

Or Will the destructor of the map be called when the
program exists? In that case I should be able to see log

Yes, if it exits. If it sits running for a long time
instead, it won't.

Well as of now I cannot use Boost because to get those
libraries into projects I will require lot of approvals.

If you need a reference counted pointer, and can't use Boost,
it's pretty easy to implement a simplified version which would
be adequate for this case. I don't really think you need a
reference counted pointer here, however. Or any pointer, for
that matter.

How can I ensure that it is getting destroyed?

First: why do want to ensure that it is getting destroyed. I
often go out of my way to ensure that objects with conceptually
static lifetimes aren't destroyed. All destruction brings is
order of destructor problems.

Second: if you put maps, and not pointers, into the outer map,
everything will automatically be destructed, at least if you
return from main() or call exit(). (If you call abort(), or if
your program terminates because of a core dump, or a system
crash, or a power failure, or... destructors will not be

You told Yes. Then at what point I should release them?

Do I have to iterate over the outer map and delete the nested
maps and then invoke a clear on the outer map?

No. Static objects will automatically be destructed at (clean)
program shutdown.

James Kanze (GABI Software)
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