RFR: JDK-8301354: Modernize utilities/breakpoint.hpp [v4]

[Thomas Stuefe]

On Mon, 30 Jan 2023 17:09:23 GMT, Justin King <jcking at openjdk.org> wrote:

>> Cleanup `utilities/breakpoint.hpp` by utilizing compiler intrinsics when available, or normal signals for AIX/XLC.
>
> Justin King has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix reference to unqualified breakpoint
>   
>   Signed-off-by: Justin King <jcking at google.com>

Hi Justin,

please note that at least on PPC platforms we use SIGTRAP for implicit null checks; so gcc debug trap won't work as expected.

Also, IIUC this changes os::breakpoint() on GCC platforms and AIX from being a manual opt-in to an unconditional trap right? While this is more in sync with what we do on Windows, this behavior has been in there a long time and may confuse people.

Finally, there is this worrying info: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84595 where it seems the GCC optimizes everything after a trap away? Can that happen with debugtrap too?

..Thomas

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PR: https://git.openjdk.org/jdk/pull/12296