RFR: 8343698: Linux x86_64 lto build gives a lot of warnings and fails lto-wrapper: fatal error: make returned 2 exit status [v2]

[Magnus Ihse Bursie]

On Mon, 18 Nov 2024 08:47:24 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

>> I asked the same question.  But as further discussion has indicated, we might need this define for
>> disabling the poisoning of selected C library functions when building with LTO, because LTO doesn't
>> support the mechanism used for that.
>
> I think all JVM features have these INCLUDE macros so I wanted to add it it for this JVM feature too. But I can remove it from the PR if it is just wanted for the other JVM features but not this one for some reason.

Yeah, the `link-time-opt` feature is a bit different from the others -- it does not select a different set of sources to be compiled, but affects how the JVM is compiled/linked. I don't think there is a need to define these preprocessor macros just out of pure symmetry reason.

If it turns out in the future that we need to compile code differently, then we can add these defines at that time.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22069#discussion_r1846196202