for 1) you mean
>
> char *CGetPath() {
> return getpath().c_str();
> }
this code will work ?
2017-04-19 14:43 GMT+08:00 Konstantin Khomoutov <
flatw...@users.sourceforge.net>:
> On Wed, 19 Apr 2017 14:23:09 +0800
> hui zhang <fastfad...@gmail.com> wrote:
>
> > 1) getpath() return a temp string, its c_str() pointer will be
> > free out of function. So I use malloc
>
> I'm not completely sure you're correct. C++ does not implement garbage
> collection and the object on which you have called c_str() continues to
> live on after getpath() returns. Now let's cite the manual on c_str():
>
> | The pointer obtained from c_str() may be invalidated by:
> | * Passing a non-const reference to the string to any standard library
> | function, or
> | * Calling non-const member functions on the string, excluding
> | operator[], at(), front(), back(), begin(), rbegin(), end() and
> | rend().
>
> So I'd say in the sequence of calls I propose there's no chance of
> anything quoted to happen -- basically the pointer returned by c_str()
> gets passed to Go where C.GoString() copies the memory pointed to by it.
>
> Things may break if you somehow concurrently call into your C++ side
> and those calls may access the same std::string object we're talking
> about. But if you do this, all bets are already off.
>
> > 2) Assume we use the malloc way , are C.GoString() copying the
> > pointer memory ? for we need C.free() malloc memory.
>
> Yes, C.GoString() copies the memory.
>
> Yes, you always need to free() what was malloc()ed for you -- because
> you own the returned pointer.
>
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