RFR: 8307316: Let JavaFX be built on unknown architectures [v2]

[John Neffenger]

On Mon, 22 May 2023 21:24:18 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> John Neffenger has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:
>> 
>>  - Merge branch 'master' into allow-armhf-i386-ppc64el-s390x
>>  - Warn instead of failing on unknown architectures
>>  - Merge branch 'master' into allow-armhf-i386-ppc64el-s390x
>>  - Merge branch 'master' into allow-armhf-i386-ppc64el-s390x
>>  - Allow building on armhf, i386, ppc64el, and s390x
>
> buildSrc/linux.gradle line 48:
> 
>> 46:         "-Wextra", "-Wall", "-Wformat-security", "-Wno-unused", "-Wno-parentheses", "-Werror=trampolines"] // warning flags
>> 47: 
>> 48: if (OS_ARCH == "i386") {
> 
> Why was this change needed, and is it sufficient? It seems that there is a larger problem (likely out of scope for this fix) as to how `IS_64` is set that might need follow-up.

The change was needed because the `-m32` option is appropriate only for the `i386` architecture. I believe the change is sufficient, but there does seem to be a problem in how the `IS_64` property is set and used throughout the build files. The property is set with:


ext.IS_64 = OS_ARCH.toLowerCase().contains("64")


Among the Java architecture names known to the build file or supported by Debian, that means:

* `IS_64` is true for `amd64`, `aarch64`, `ppc64le`, `loongarch64`, and  `riscv64`, while
* `IS_64` is false for `arm`, `i386`, and `s390x`.

The previous code, then, would set the `-m32` option for `arm`, `i386`, and `s390x`. Yet the option is valid only for the [following target machines][1]:

* RS/6000 and PowerPC (Debian `powerpc`)
* SPARC (Debian `sparc`)
* x86 (Debian `i386`)

So as long as nobody wants to build JavaFX for the 32-bit PowerPC or 32-bit SPARC architectures, the code change is fine. I don't know of anyone still supporting operating systems with Java on those architectures, so we should be safe.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Option-Summary.html

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

PR Review Comment: https://git.openjdk.org/jfx/pull/1124#discussion_r1230020859