forwarded to other teams for review. On Fri, Dec 13, 2019 at 3:14 AM Patrick Zhang OS < patr...@os.amperecomputing.com> wrote:
> Hi > > Please review this patch, if it should be reviewed by any group other than > core-libs, please help forward it. Thanks. > > JBS: https://bugs.openjdk.java.net/browse/JDK-8235903 > Webrev: http://cr.openjdk.java.net/~qpzhang/8235903/webrev.01/ > > A recent GCC patch (supposed to be in GCC 10) exposes a couple of > "multiple definition" link errors when building the jdk tip. > > [PATCH] PR85678: Change default to -fno-common > https://gcc.gnu.org/ml/gcc-patches/2019-10/msg01847.html > > For example, the error message looks like: > * For target support_native_java.base_libjava_BUILD_LIBJAVA_link: > build/support/native/java.base/libjava/childproc.o:(.bss+0x0): multiple > definition of `parentPathv' > build/support/native/java.base/libjava/ProcessImpl_md.o:(.bss+0x0): first > defined here > collect2: error: ld returned 1 exit status > > This was not an issue because the original default -fcommon allowed > "global variables defined without an initializer" be handled as COMMON > symbols, so it would not warn the problem like "same variable is > accidentally defined in more than one compilation unit". > > About -fcommon vs -fno-cmmon: > https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html#index-fno-common > > Moving forward, building jdk with latest versions of GCC will trigger this > error. Specifying "--with-extra-cflags='-fcommon'" can make it work, but > it just got things hidden again. > > In addition, -fcommon's behavior "is inconsistent with C++, and on many > targets implies a speed and code size penalty on global variable > references. It is mainly useful to enable legacy code to link without > errors." > > Last, in case that other jdk developers would revisit this problem once > again, I suggest fixing the error explicitly instead of using "-fcommon" > > Regards > Patrick > >
