RFR: 8294308: Allow dynamically choosing the MEMFLAGS of a type without ResourceObj

[Coleen Phillimore]

On Fri, 23 Sep 2022 17:08:46 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

> Here's a suggested solution for the ticket mentioned and a use case for outputStream. I'm not attached to the name.
> 
> This saves space for all allocated outputStreams, which is nice. It also makes the purpose of ResourceObj more clear ("please handle the life cycle for me"), reducing the need for it.
> 
> Thank you for considering it.

src/hotspot/share/memory/allocation.hpp line 219:

> 217: };
> 218: 
> 219: class DynCHeapObj {

I tried this and it seems to work:  If you make CHeapObj new operators take MEMFLAGS f = F, where F is the default  value, you could not have this class and make outputStream inherit from CHeapObj<mtInternal> and the new calls will override mtInternal.  I guess the risk is that you get mtInternal if you forget the parameter to new.

src/hotspot/share/opto/compile.cpp line 4413:

> 4411:     // print_inlining_init is actually called several times.
> 4412:     print_inlining_stream_free();
> 4413:     _print_inlining_stream = new (mtCompiler) stringStream();

These now need a delete (which is good because it doesn't need an explicit destructor call).

-------------

PR: https://git.openjdk.org/jdk/pull/10412