[GiNaC-list] GiNaC and malloc()

[Igor Khavkine]

On 6/27/06, Richard B. Kreckel <kreckel at ginac.de> wrote:

> I don't think you can get around those "extra steps" you mention.  In
> C++, one has placement new for directed allocating.  But you would have
> to write some additional code between #ifdefs to use it instead of
> malloc(3).  And even doing so would not spare you extra destructor calls
> to avoid leaks.  This function does not leak:

Ah, I didn't know about this feature of the new operator. It seems to
do exactly what I want. Thanks!

> void f(size_t n)
> {
>     char buf[n*sizeof(GiNaC::ex)];  // you manage that memory!
>     for (size_t i=0; i<n; ++i) {
>         new(&buf[i*sizeof(GiNaC::ex)]) GiNaC::ex(2);
>     }
>
>     //...
>     cout << *reinterpret_cast<GiNaC::ex*>(&buf[0 * sizeof(GiNaC::ex)])
> << endl;
>     //...
>
>     // It is your responsibility to keep track of the reference counts:

Calling destructors is not a big deal. Do you mean anything else by
"reference counts"? I couldn't find any documented way to access the
reference counting information that GiNaC keeps internally.

>     for (size_t i=0; i<n; ++i) {
>         reinterpret_cast<GiNaC::ex*>(&buf[i*sizeof(GiNaC::ex)])->~ex();
>     }
> }
>
> Not sure if this helps.

Very much so. Thanks again!

Igor