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

[David Holmes]

On 3/04/2015 2:06 AM, Volker Simonis wrote:
> Hi,
>
> while precompiled headers (PCH) are a nice and effective way of
> improving hotspot build times this feature also drastically increases

IIUC PCH benefits incremental build times, not clean builds. It's useful 
for developer builds but not JPRT builds (or any official build).

> the risk of introducing missing dependencies into the source base.
> This is especially annoying on platforms where precompield headers
> aren't available at all.
>
> In the last two weeks we had two cases [1,2] of such missing
> dependencies which haven't been caught by JPRT because JPRT uses the
> default platform settings and thus always uses PCHs on all platforms
> where they are supported.
>
> I want to strongly advocate for a change in the JPRT configurations
> such that at least on one Windows and one Linux platform the automatic
> pre-integration builds are done with
> "--with-debug-level=[slow/fast]debug --disable-precompiled-headers".

One of the main areas where PCH hides problems is with the minimal VM, 
unfortunately the only builds that build the minimal VM are the embedded 
builds. Arguably we could add the minimal VM to a linux x86 build but we 
need to look at overall build times etc before making that the default.

David

> This simple change which comes at the minor cost of a few CPU-cycles
> will save a big amount of (hopfully) much more precious developer
> cycles and at the same time considerably improve the code quality.
> Notice that I intentionally ask for a *debug build without PCHs
> because debug builds exercise much more source code and are
> specifically prone to missing include dependency errors.
>
> As this change can only be decided upon and implemented inside Oracle
> I hereby kindly ask for an appropriate sponsor.
>
> Thank you and best regards,
> Volker
>
> [1]
> Introduced by: https://bugs.openjdk.java.net/browse/JDK-8075416
> Fixed by: https://bugs.openjdk.java.net/browse/JDK-8075735
>
> [2]
> Introduced by: https://bugs.openjdk.java.net/browse/JDK-8076314
> Fix proposed: http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2015-April/012659.html
>