The History of nortti and noeh on AIX

[Thomas Stüfe]

Yes, hotspot don't need it. AFAIK its disabled on all platforms.

See:

https://github.com/openjdk/jdk/blob/master/doc/hotspot-style.md#error-handling
https://github.com/openjdk/jdk/blob/master/doc/hotspot-style.md#rtti-runtime-type-information

C++ exception stack unwinding would probably fail in the face of our mixed,
non-ABI-conform stacks. And RTTI is just not needed, why pay for it.

Cheers, Thomas



On Thu, Jun 22, 2023 at 11:40 AM Baesken, Matthias <matthias.baesken at sap.com>
wrote:

> Hi Tyler, we had the flags  -qnoeh  and -qnortti   already  set  before
> 2010 in our internal  AIX build  (some time  before the  AIX OpenJDK port
> started).
>
> Probably the features were not needed in those ancient times .
>
>
>
> I took over the flags  when doing the xlc16 support changes in OpenJDK .
>
>
>
> Best regards, Matthias
>
>
>
>
>
> *From:* ppc-aix-port-dev <ppc-aix-port-dev-retn at openjdk.org> *On Behalf
> Of *Tyler Steele
> *Sent:* Wednesday, 21 June 2023 20:31
> *To:* ppc-aix-port-dev at openjdk.org
> *Subject:* The History of nortti and noeh on AIX
>
>
>
> Hi all,
>
>
>
> I was recently asked [1] why we include -qnoeh [2] and -qnoftti [3] with
> the build. It looks like it's been in the project since at least jdk9 [4],
> but I suspect that might not be the true origin of the flags.
>
>
>
> Reading the descriptions for the flags makes me suspect that these were
> added to improve performance "For improved runtime performance, suppress
> RTTI information generation with the -qnortti setting." [2] and possibly
> to reduce code bloat "If your program does not use C++ structured exception
> handling, you can compile with -qnoeh to prevent generation of code that
> is not needed by your application." [3]. But these are just guesses. Any
> chance that anyone out there knows/remembers why these were added?
>
>
>
> Tyler
>
>
>
> [1]
> https://github.com/adoptium/adoptium-support/issues/824#issuecomment-1599049333
>
> [2]
> https://www.ibm.com/docs/en/xl-c-and-cpp-aix/16.1?topic=descriptions-qrtti-qnortti-fno-rtti-c-only
>
> [3]
> https://www.ibm.com/docs/en/xl-c-and-cpp-aix/16.1?topic=descriptions-qeh-fexceptions-c-only#opt_eh
>
> [4]
> https://github.com/openjdk/jdk/commit/e709aa268df64b2dc000433a1d9621a2fb0940f0
>
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