[8u] RFR: JDK-8152545 Use preprocessor instead of compiling a program to generate native nio constants

[Andrew Hughes]

On 09:54 Tue 22 Sep     , Andrew Haley wrote:
> On 28/02/2020 18:06, Simon Tooke wrote:
> > Hello,
> > 
> > I would like to request approval to backport of JDK-8152545 (Use 
> > preprocessor instead of compiling a program to generate native nio 
> > constants) to jdk8u for buildability reasons.  I've personally 
> > encountered toolchains where the current solution doesn't build.
> > 
> > I had to modify the original webrev to get rid of the SO_REUSEPORT 
> > definition, as it isn't supported in JDK8.
> > 
> > I've tested this on Windows and macos.
> > 
> > Bug: https://bugs.openjdk.java.net/browse/JDK-8152545
> > 
> > Original patch: http://hg.openjdk.java.net/jdk9/jdk9/jdk/rev/e2e318304252
> > 
> > Modified webrev: 
> > http://cr.openjdk.java.net/~stooke/webrevs/jdk-8152545-jdk8/02/jdk.02
> 
> Why is this being backported? There's no explanation in the bug report
> and it doesn't seem to fit any of the usual criteria for a backport.
> 
> -- 
> Andrew Haley  (he/him)
> Java Platform Lead Engineer
> Red Hat UK Ltd. <https://www.redhat.com>
> https://keybase.io/andrewhaley
> EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671
> 

I see explanations for this in both this e-mail and in the comments on
the bug report.  There is also further detail in the comments of the
linked bug,

https://bugs.openjdk.java.net/browse/JDK-8072664

and there's also:

https://bugs.openjdk.java.net/browse/JDK-8150529

Having to run a C program to generate the native constant files doesn't
work when cross-compiling. Just running the preprocessor will work and
is all that is needed.

I think this is very low-risk (the post-patch output files can be
compared against the pre-patch output files) and, as Aleksey says
on the bug, avoids the need to try and hack around this when
cross-compiling.

The aarch64/shenandoah-jdk8u tree has been carrying this hack for
JDK-8072664 since December 2013:

--- jdk8/jdk/make/gensrc/GensrcMisc.gmk	2019-12-04 15:06:20.035798777 +0000
+++ shenandoah.8/jdk/make/gensrc/GensrcMisc.gmk	2019-12-04 15:29:56.300960990 +0000
@@ -76,7 +76,7 @@
     INCLUDE_FILES := $(GENSRC_SOR_SRC_FILE), \
     LANG := C, \
     CC := $(BUILD_CC), \
-    LDEXE := $(BUILD_LD), \
+    LDEXE := $(BUILD_CC), \
     OBJECT_DIR := $(GENSRC_SOR_BIN), \
     OUTPUT_DIR := $(GENSRC_SOR_BIN), \
     PROGRAM := genSocketOptionRegistry))

Thanks,
-- 
Andrew :)

Senior Free Java Software Engineer
OpenJDK Package Owner
Red Hat, Inc. (http://www.redhat.com)

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