From 42735cb9b9ca8290ee0566b4e1dce9d5ca2ed036 Mon Sep 17 00:00:00 2001 From: Thomas Petazzoni Date: Sun, 6 Mar 2016 21:47:16 +0100 Subject: [PATCH] toolchain: introduce BR2_TOOLCHAIN_HAS_LIBATOMIC Until now, we were assuming that whenever you have gcc 4.8, libatomic is available. It turns out that this is not correct, since libatomic will not be available if thread support is disabled in the toolchain. Therefore, __atomic_*() intrinsics may not be available even if the toolchain uses gcc 4.8. To solve this problem, we introduce a BR2_TOOLCHAIN_HAS_LIBATOMIC boolean, which indicates whether the toolchain has libatomic. It is the case when you are using gcc >= 4.8 *and* thread support is enabled. We then use this new BR2_TOOLCHAIN_HAS_LIBATOMIC to define BR2_TOOLCHAIN_HAS_ATOMIC. As explained in the comment, on certain architectures, libatomic is technically not needed to provide the __atomic_*() intrinsics since they might be all built-in. However, since libatomic is only absent in non-thread capable toolchains, it is not worth making things more complex for such seldomly used configuration. Note that we are introducing the intermediate BR2_TOOLCHAIN_HAS_LIBATOMIC option because it will be useful on its own for certain packages. Signed-off-by: Thomas Petazzoni [Thomas: improve Config.in comment using a suggestion from Yann.] --- toolchain/toolchain-common.in | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/toolchain/toolchain-common.in b/toolchain/toolchain-common.in index 46970a68e3..0907c5e830 100644 --- a/toolchain/toolchain-common.in +++ b/toolchain/toolchain-common.in @@ -378,15 +378,30 @@ config BR2_TOOLCHAIN_HAS_SYNC_8 default y if BR2_TOOLCHAIN_ARM_HAS_SYNC_8 default y if BR2_TOOLCHAIN_X86_HAS_SYNC_8 +# libatomic is available since gcc 4.8, when thread support is +# enabled. +config BR2_TOOLCHAIN_HAS_LIBATOMIC + bool + default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 && \ + BR2_TOOLCHAIN_HAS_THREADS + # __atomic intrinsics are available: # - with gcc 4.8, either through built-ins or libatomic, on all -# architectures +# architectures. Since we don't want to separate the cases where +# libatomic is needed vs. not needed, we simplify thing and only +# support situations where libatomic is available, even if on some +# architectures libatomic is not strictly needed as all __atomic +# intrinsics might be built-in. The only case where libatomic is +# missing entirely is when the toolchain does not have support for +# threads. However, a package that does not need threads but still +# uses atomics is quite a corner case, which does not warrant the +# added complexity. # - with gcc 4.7, libatomic did not exist, so only built-ins are # available. This means that __atomic can only be used in a subset # of the architectures config BR2_TOOLCHAIN_HAS_ATOMIC bool - default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 + default y if BR2_TOOLCHAIN_HAS_LIBATOMIC default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 && BR2_arm default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 && BR2_armeb default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 && BR2_xtensa -- 2.30.2