[Ace-users] [tao-users] Is strdup required for return and out parameters

Christian Fromme christian at ast.dfs.de
Fri Oct 19 01:08:03 CDT 2007

On 18.10. 17:02, Tommy Persson wrote:
> Chris Cleeland <cleeland at ociweb.com> writes:
> > On Oct 18, 2007, at 7:40 AM, Vikram Karandikar wrote:
> > 
> > > So either i should use strdup or CORBA::string_dup but stick to one.
> > > am i right?
> > 
> > No, you should use only CORBA::string_dup() when duplicating CORBA
> > strings.
> > 
> > Consult the Henning & Vinoski book suggested by Christian for details
> > and further information.
> I have read the book but totally misssed this. So could you indicate
> where it is discussed or why?

Please see the first mail I wrote in this thread, the chapters are
referenced there.

> In page 147 i says that
>     char * p = CORBA::string_dup ("Hello");
> is correct code but "Hello" is not a CORBA::String. And I routinely do
> things like
>    return CORBA::string_dup (res.c_str());
> So what is the problem with this construction?

Of course, the answer depends on the return type of your function there.
You may want to take a look at the implementation of CORBA::string_dup
in TAO. It simply allocates (char *) memory of the size of the original
string, copies original to newly allocated and returns a char * to the
allocated string. Pretty straightforward and save.

If the function above is expected to return CORBA::String_var, you're 
fine. The caller takes ownership of your newly allocated string and 
takes care of the de-allocation later. Doing a ._retn() on a 
CORBA::String_var would also be fine here.

Christian Fromme

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