src/hotspot/os_cpu/linux_riscv/riscv_flush_icache.cpp: In static member function 'static bool RiscvFlushIcache::test()':
src/hotspot/os_cpu/linux_riscv/riscv_flush_icache.cpp:51:29: error: requested alignment 64 is larger than 16 [-Werror=attributes]
   51 | alignas(64) char memory[64];
      | ^
cc1plus: all warnings being treated as errors

standalone g++ command:
/usr/local/bin/ccache /opt/riscv_toolchain_linux/bin/riscv64-unknown-linux-gnu-g++ -MMD -MF build/linux-riscv64-server-release/hotspot/variant-server/libjvm/objs/riscv_flush_icache.d.tmp -fpch-preprocess -Ibuild/linux-riscv64-server-release/hotspot/variant-server/libjvm/objs/precompiled -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -D__STDC_CONSTANT_MACROS -D_GNU_SOURCE -D_REENTRANT -pipe -fno-rtti -fno-exceptions -fvisibility=hidden -fno-strict-aliasing -fno-omit-frame-pointer -fstack-protector -std=c++14 -DLIBC=gnu -DLINUX -D_FILE_OFFSET_BITS=64 -Wall -Wextra -Wformat=2 -Wpointer-arith -Wreturn-type -Wsign-compare -Wtrampolines -Wundef -Wunused-const-variable=1 -Wunused-function -Wunused-result -Wunused-value -Woverloaded-virtual -Wreorder -fPIC -fmacro-prefix-map=/home/yansendao/git/jdk-ysd/= -DVM_LITTLE_ENDIAN -D_LP64=1 -fno-lifetime-dse -Wno-format-zero-length -Wtype-limits -Wuninitialized -DNDEBUG -DPRODUCT -DTARGET_ARCH_riscv -DINCLUDE_SUFFIX_OS=_linux -DINCLUDE_SUFFIX_CPU=_riscv -DINCLUDE_SUFFIX_COMPILER=_gcc -DTARGET_COMPILER_gcc -DRISCV64 '-DHOTSPOT_LIB_ARCH="riscv64"' -DCOMPILER1 -DCOMPILER2 -DDTRACE_ENABLED -Ibuild/linux-riscv64-server-release/hotspot/variant-server/gensrc/adfiles -Isrc/hotspot/share -Isrc/hotspot/os/linux -Isrc/hotspot/os/posix -Isrc/hotspot/cpu/riscv -Isrc/hotspot/os_cpu/linux_riscv -Ibuild/linux-riscv64-server-release/hotspot/variant-server/gensrc -Isrc/hotspot/share/precompiled -Isrc/hotspot/share/include -Isrc/hotspot/os/posix/include -Ibuild/linux-riscv64-server-release/support/modules_include/java.base -Ibuild/linux-riscv64-server-release/support/modules_include/java.base/linux -Isrc/java.base/share/native/libjimage -Ibuild/linux-riscv64-server-release/hotspot/variant-server/gensrc/adfiles -Isrc/hotspot/share -Isrc/hotspot/os/linux -Isrc/hotspot/os/posix -Isrc/hotspot/cpu/riscv -Isrc/hotspot/os_cpu/linux_riscv -Ibuild/linux-riscv64-server-release/hotspot/variant-server/gensrc -Ibuild/linux-riscv64-server-release/support/modules_include/java.base -Isrc/java.base/unix/native/include -Isrc/java.base/share/native/include -g -gdwarf-4 -fdebug-prefix-map=/home/yansendao/git/jdk-ysd/= -fdebug-prefix-map=/opt/fedora28_riscv_root/usr/include/=/usr/include/ -fdebug-prefix-map=/opt/riscv_toolchain_linux/lib/gcc/riscv64-unknown-linux-gnu/9.2.0/include/=/usr/local/gcc_include/ -fdebug-prefix-map=/opt/riscv_toolchain_linux/riscv64-unknown-linux-gnu/include/c++/9.2.0/=/usr/local/gxx_include/ -fdebug-prefix-map=/home/yansendao/git/jdk-ysd/build/linux-riscv64-server-release/= -Wno-unused-parameter -Wno-array-bounds -Wno-comment -Wno-delete-non-virtual-dtor -Wno-empty-body -Wno-implicit-fallthrough -Wno-int-in-bool-context -Wno-maybe-uninitialized -Wno-missing-field-initializers -Wno-shift-negative-value -Wno-unknown-pragmas -Wno-unused-but-set-variable -Wno-unused-local-typedefs -Wno-unused-variable -Werror --sysroot=/opt/fedora28_riscv_root -O3 -c -o build/linux-riscv64-server-release/hotspot/variant-server/libjvm/objs/riscv_flush_icache.o src/hotspot/os_cpu/linux_riscv/riscv_flush_icache.cpp -frandom-seed=riscv_flush_icache.cpp

configure command:
bash configure --with-jobs=128 --prefix=/home/yansendao/git/jdk-ysd/install-release --verbose --with-debug-level=release --enable-unlimited-crypto --with-vendor-name=yansendao --with-vendor-url=https://github.com/sendaoYan --with-vendor-bug-url=mailto:yansendao.ysd@alibaba-inc.com --with-vendor-vm-bug-url=mailto:yansendao.ysd@alibaba-inc.com --with-jvm-variants=server --with-boot-jdk=/home/yansendao/software/jdk/openjdk/jdk-binary --with-gtest=/home/yansendao/git/googletest-v1.14.x --with-jtreg=/home/yansendao/software/jdk/jtreg-7.4 --with-jmh=build/jmh/jars --with-version-pre='' --with-version-opt=52ba7282 --with-zlib=system --enable-ccache