[jdk8u-dev] RFR: 8281096: Flags introduced by configure script are not passed to ADLC build [v5]

[Andrew John Hughes]

On Sat, 17 Feb 2024 20:29:09 GMT, Andrew John Hughes <andrew at openjdk.org> wrote:

>> The 8u configure script defines compiler flags in `EXTRA_CFLAGS`, `EXTRA_LDFLAGS` and `EXTRA_ASFLAGS`. Some are added by configure tests, while others are taken directly from corresponding options passed by the user.
>> 
>> 8u still use the legacy HotSpot build system which is not fully integrated with the autoconf system. Variables defined by configure thus have to be explicitly passed down to the separate HotSpot build.
>> 
>> ADLC is a tool used at build-time and so the flags it uses don't impact on the end product. So, for a long time, it has been ignoring these flags defined by configure and using just its own minimal set.
>> 
>> However, with newer compilers, this means that the code is compiled to a newer version of the C++ standard, as the default has changed in GCC 6 and later (see [JDK-8151841](https://bugs.openjdk.org/browse/JDK-8151841)). With the latest versions of GCC (11 and 12), this actually leads to build failures due to the use of 'register' (GCC 11) and the way comments are used (GCC 12) in the code.
>> 
>> We should fix the ADLC build to use the same flags as the rest of the build. The impact should be negligible, given the same flags are already used in the code that is actually shipped.
>> 
>> This does not affect 9+ where HotSpot's build system has been replaced with full integration in the autoconf system.
>> 
>> With this change, 8u can be built with GCC 11 on GNU/Linux. I'd appreciate testing on other platforms, particularly those not covered by GHA (Solaris, AIX - @adamfarley, @sxa & @deepa181 who have provided previous fixes for these platforms)
>
> Andrew John Hughes has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Print spec files in right workflow and use path to build directory

I think I know what's wrong here now with the cross-compilation builds. The `EXTRA_CFLAGS` that HotSpot gets end up including the `--sysroot` options on cross-compile builds, which are really destined for the target compiler, not a build compiler which is compiling a build tool that is going to be run during the build.

I can fix this, but it's going to make this fix a bit more involved than I initially thought.

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PR Comment: https://git.openjdk.org/jdk8u-dev/pull/357#issuecomment-1952881691