We REALLY nead a NON-PCH build in JPRT NOW!

[Stefan Karlsson]

Volker,

On 2015-05-08 16:42, Volker Simonis wrote:
> On Thu, Apr 23, 2015 at 1:42 AM, Coleen Phillimore
> <coleen.phillimore at oracle.com> wrote:
>> On 4/22/15, 3:57 AM, Andrew Haley wrote:
>>> On 22/04/15 03:01, Daniel D. Daugherty wrote:
>>>> Personally, I like the idea of not adding any more new JPRT targets
>>>> and reconfiguring to have fastdebug and/or debug builds run as non-PCH...
>>>> It's a much simpler policy to explain:
>>>>
>>>>        If we support PCH builds with a particular toolset then product
>>>>        builds default to PCH and non-product builds default to no-PCH.
>>> But the debug builds are used in development all the time.  It's
>>> these that really benefit from PCH.
>>
>> I feel like PCH makes development slower.  I change a header file and all
>> the files in the system are recompiled because it happens to be in the
>> precompiled file.  I wouldn't miss it for debug mode.
>>
> While working on the new HotSpot build (in the build-infra project)
> I've just realized the we are currently using the option '-fpch-deps'.
>
> Citing from the gcc man-page: "When using precompiled headers, this
> flag will cause the dependency-output flags to also list the files
> from the precompiled header's dependencies.  If not specified only the
> precompiled header would be listed and not the files that were used to
> create it because those files are not consulted when a precompiled
> header is used."
>
> This actually means that a .cpp file which uses PCH will depend on all
> the headers in the PCH-file while while it should actually only depend
> an the header files it explicitly includes itself. So this is probably
> the reason why with PCH the change of a single header unnecessarily
> triggers the recompilation of most of the
> .cpp files. That said we of course still have certain header which are
> included in all compilation units so there's nothing we can make once
> such a file is changed.

Yes, I think you found that running without -fpch-deps was broken:
http://mail.openjdk.java.net/pipermail/hotspot-dev/2012-June/006016.html

:)

StefanK

>
>
>> Coleen
>>
>>> Andrew.
>>>