RFR: 8256486: Linux/Windows-x86 builds broken after JDK-8254231 [v4]

[Aleksey Shipilev]

On Mon, 23 Nov 2020 20:36:11 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> JDK-8254231 breaks the Linux and Windows x86 (32-bit) builds. This contains the needed changes to get it working again.
>> 
>> Perhaps the most interesting change is adding the `JNI_ENTRY_CPP_NOENV` macro. Using just JNI_ENTRY was causing a linkage failure, due to the declaration of the function in the class not having the same linkage specifiers. It looks like we can't just specify C linkage for class member functions.
>> 
>> However, in this case C linkage is not required, so I've added the new macro which doesn't have `extern "C"`. I've also dropped the `JNIEnv*` parameter, since it was not being used, but causing extra work for the caller.
>> 
>> Other than that, it's just about adding default definitions for missing functions, and moving around some code in MacroAssembler to be in the correct `#ifdef` blocks.
>> 
>> Testing: `make images` on Linux and Windows x86_32 platforms.
>
> Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use the Unimplemented() macro instead of hlt()

I have a few minor comments, in addition to what David is saying about `JNI_ENTRY_CPP_NOENV`.

src/hotspot/cpu/x86/macroAssembler_x86.cpp line 497:

> 495: void MacroAssembler::reset_last_Java_frame(bool clear_fp) {
> 496:   reset_last_Java_frame(r15_thread, clear_fp);
> 497: }

I see that before the Foreign Linker integration, this method was between `MacroAssembler::pushptr` and `MacroAssembler::set_last_Java_frame`. Please move it back there.

-------------

Changes requested by shade (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1266