RFR: 8352284: EXTRA_CFLAGS incorrectly applied to BUILD_LIBJVM src/hotspot C++ source files [v2]

[Magnus Ihse Bursie]

On Sat, 22 Mar 2025 10:09:46 GMT, Patrick Zhang <qpzhang at openjdk.org> wrote:

>> Building jdk with `--with-extra-cflags='-Wno-incompatible-pointer-types'` triggers 1000+ warning messages like `cc1plus: warning: command-line option ‘-Wno-incompatible-pointer-types’ is valid for C/ObjC but not for C++`. 
>> 
>> The root cause is that `JVM_CFLAGS ` which contains both `EXTRA_CXXFLAGS` and `EXTRA_CFLAGS` when compiling `src/hotspot` C++ source files and building `BUILD_LIBJVM`.
>> 
>> This PR does:
>> 1. Not to append `EXTRA_CFLAGS` or `EXTRA_CXXFLAGS` into `JVM_CFLAGS` before calling `SetupJdkLibrary`, instead let `SetupCompilerFlags` accept and merge `EXTRA_CFLAGS` and `EXTRA_CXXFLAGS` passed from `SetupJdkLibrary` as parameters, so CPP compilation will only see `EXTRA_CXXFLAGS` as expected.
>> 2. Correct `PCH_COMMAND` to use `EXTRA_CXXFLAGS` as precompiled.hpp.gch should not be compiled with `EXTRA_CFLAGS`.
>> 3. Fixed `STATIC_LIB_CFLAGS` in `Flags.gmk` to `-DSTATIC_BUILD=1`, which was missed by [cbab40bc](https://github.com/openjdk/jdk/commit/cbab40bce45a2f58906be49c841178fa1dfd457e#diff-ab3ce05e795360030f19402fd0c2fad1dc1f7c5e7acc993cc4a2096cf31ccf40R114-R121) for the refactor of building static libs.
>> 
>> Tests: Passed jdk building on an AArch64 Linux system and tier1 sanity tests, also passed OpenJDK GHA Sanity Checks.
>
> Patrick Zhang has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - Fixed a typo
>    
>    Signed-off-by: Patrick Zhang <patrick at os.amperecomputing.com>
>  - Added comments to describe why EXTRA_CFLAGS is excluded from JVM_CFLAGS
>    
>    Signed-off-by: Patrick Zhang <patrick at os.amperecomputing.com>
>  - Revert the changes of adding new params to SetupNativeCompilation
>    
>    Signed-off-by: Patrick Zhang <patrick at os.amperecomputing.com>

make/hotspot/lib/JvmFlags.gmk line 89:

> 87: endif
> 88: 
> 89: # Hotspot currently supports only C++. To prevent compilation conflicts,

I don't think this comments serves any purpose. It was probably a mistake to include EXTRA_CFLAGS here to begin with. After this PR, no one is going to miss it, so the comment will make no sense.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24115#discussion_r2010743373