From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Petazzoni Date: Fri, 5 Feb 2016 00:06:13 +0100 Subject: [Buildroot] [PATCH 1/1] protobuf: apply patch to compile for PowerPC In-Reply-To: <1453986515-9505-1-git-send-email-casantos@datacom.ind.br> References: <1453986515-9505-1-git-send-email-casantos@datacom.ind.br> Message-ID: <20160205000613.504940f9@free-electrons.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net Carlos, On Thu, 28 Jan 2016 11:08:35 -0200, Carlos Santos wrote: > From: Henrique Marks > > Signed-off-by: Henrique Marks > Signed-off-by: Carlos Santos > --- > package/protobuf/0001-PowerPC-Support.patch | 54 +++++++++++++++++++++++++++++ > package/protobuf/Config.in | 5 ++- > 2 files changed, 56 insertions(+), 3 deletions(-) > create mode 100644 package/protobuf/0001-PowerPC-Support.patch This patch doesn't actually work. First there are a number of problems: - The patch you apply has technically nothing to do with enabling the PowerPC architecture. It seems more related to supporting old compilers. - The patch you apply is already applied upstream, so in this case, we prefer to use the upstream patch directly. - You change the architecture dependencies in protobuf/Config.in, but forget to propagate this change to the reverse dependencies of protobuf, namely the mosh and ola packages. To make this easier, I've changed protobuf/Config.in to provide a BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS variable, and changed mosh and ola to use it. See commit https://git.busybox.net/buildroot/commit/?id=abdc56006bf253bec393066f96f69f0a6246b896. But then, despite those issues, your patch still doesn't build on PowerPC with the following defconfig for example: BR2_powerpc=y BR2_powerpc_8548=y BR2_TOOLCHAIN_EXTERNAL=y BR2_INIT_NONE=y BR2_SYSTEM_BIN_SH_NONE=y # BR2_PACKAGE_BUSYBOX is not set BR2_PACKAGE_OLA=y BR2_PACKAGE_MOSH=y # BR2_TARGET_ROOTFS_TAR is not set It fails with: In file included from ./google/protobuf/stubs/once.h:81:0, from google/protobuf/stubs/common.cc:34: ./google/protobuf/stubs/atomicops.h:209:2: error: #error GOOGLE_PROTOBUF_ATOMICOPS_ERROR In file included from ./google/protobuf/stubs/once.h:81:0, from google/protobuf/stubs/once.cc:38: ./google/protobuf/stubs/atomicops.h:209:2: error: #error GOOGLE_PROTOBUF_ATOMICOPS_ERROR In file included from google/protobuf/stubs/atomicops_internals_x86_msvc.cc:37:0: ./google/protobuf/stubs/atomicops.h:209:2: error: #error GOOGLE_PROTOBUF_ATOMICOPS_ERROR In file included from google/protobuf/stubs/atomicops_internals_x86_gcc.cc:36:0: ./google/protobuf/stubs/atomicops.h:209:2: error: #error GOOGLE_PROTOBUF_ATOMICOPS_ERROR Looking at atomicops.h, I can read: #elif defined(__GNUC__) #if defined(GOOGLE_PROTOBUF_ARCH_IA32) || defined(GOOGLE_PROTOBUF_ARCH_X64) #include #elif defined(GOOGLE_PROTOBUF_ARCH_ARM) && defined(__linux__) #include #elif defined(GOOGLE_PROTOBUF_ARCH_AARCH64) #include #elif defined(GOOGLE_PROTOBUF_ARCH_ARM_QNX) #include #elif defined(GOOGLE_PROTOBUF_ARCH_MIPS) || defined(GOOGLE_PROTOBUF_ARCH_MIPS64) #include #elif defined(__native_client__) #include #elif (((__GNUC__ == 4) && (__GNUC_MINOR__ >= 7)) || (__GNUC__ > 4)) #include #elif defined(__clang__) #if __has_extension(c_atomic) #include #else #error GOOGLE_PROTOBUF_ATOMICOPS_ERROR #endif #else #error GOOGLE_PROTOBUF_ATOMICOPS_ERROR #endif So it means that on i386, on x86-64, on ARM and on MIPS and MIPS64, there are built-in implementation for the atomic operations. For all other architectures, it relies on atomicops_internals_generic_gcc.h, only when gcc >= 4.7. And indeed my tested toolchain only has gcc 4.5. In fact atomicops_internals_generic_gcc.h uses the __atomic_*() built-ins of the compiler, which indeed are only introduced in gcc 4.7. But on some architectures, they require linking with -latomic. See my atomic patch series at http://lists.busybox.net/pipermail/buildroot/2016-February/151672.html, and especially patch http://lists.busybox.net/pipermail/buildroot/2016-February/151674.html which has all the gory details. And in fact, with those atomics, not only PowerPC can be supported, but any other architecture (except if protobuf has other architecture-specific dependencies elsewhere). So, once my atomic patch series is merged, we could do: config BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS bool default y if BR2_arm default y if BR2_i386 default y if BR2_mipsel default y if BR2_x86_64 default y if BR2_TOOLCHAIN_HAS_ATOMIC depends on BR2_HOSTARCH = "x86_64" || BR2_HOSTARCH = "x86" *and* ensure protobuf gets linked with -latomic. What do you think ? Best regards, Thomas -- Thomas Petazzoni, CTO, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com