The History of nortti and noeh on AIX

[Baesken, Matthias]

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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