![Samuel Martin](/assets/img/avatar_default.png)
With some toolchains, using atomics requires to explicitly add -latomic to the linker flags. This change adds a patch to pulseview adding this detection and updating the LDFLAGS when appropriate. This patch has be sent upstream: http://article.gmane.org/gmane.comp.debugging.sigrok.devel/2097 Fixes: http://autobuild.buildroot.org/results/1e3/1e3101261252d5f30fdf842cc99604e4f4c25eef/build-end.log Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com> Cc: Romain Naour <romain.naour@gmail.com> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Signed-off-by: Samuel Martin <s.martin49@gmail.com> Reviewed-by: Romain Naour <romain.naour@gmail.com> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
118 lines
4.2 KiB
Diff
118 lines
4.2 KiB
Diff
From 71830c804be76cf6abe913ac2fe584947b7a91ea Mon Sep 17 00:00:00 2001
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From: Samuel Martin <s.martin49@gmail.com>
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Date: Tue, 24 May 2016 23:08:40 +0200
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Subject: [PATCH] cmake: add check for explicit linking against libatomic
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To use atomics functions, some toolchains requires to explicitly add
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-latomic to the linker flags (because they are not provided by libc,
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but libatomic).
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This change adds a helper function trying to build/link a test program
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using atomics, then calls it to:
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* first check if atomics are directly available in the libc;
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* if not and libatomic has been found, then run the same test with
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"-latomic" added to the linker flags.
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The pulseview link library list is updated according to the results of
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these tests.
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This issue was triggered by the Buildroot farms:
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http://autobuild.buildroot.org/results/1e3/1e3101261252d5f30fdf842cc99604e4f4c25eef/build-end.log
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Notes:
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1- CMAKE_REQUIRED_* variables are only used in check functions. They
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are not automatically forwarded to/handled by the target commands
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(such as target_link_library), because the check functions are
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implemented as macro in CMake code, whereas many target commands
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are native.
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2- Because of note #1, CMAKE_REQUIRED_LIBRARIES (or its value) must be
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explicitly passed to the target_link_library command when this is
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needed.
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3- In this implementation, LIBATOMIC_LIBRARY is only set when it is
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needed; so, unconditionally appending it to PULSEVIEW_LINK_LIBS
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will produce the expected behavior.
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Signed-off-by: Samuel Martin <s.martin49@gmail.com>
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---
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changes v1->v2:
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- use std::atomic_fetch_add_explicit function instead of
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__atomic_fetch_add_4;
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- rework code using cmake_*_check_state and find_library helpers;
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- quiet-ize checks and clean outputs
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- extend the commit log
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---
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CMakeLists.txt | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
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1 file changed, 50 insertions(+)
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diff --git a/CMakeLists.txt b/CMakeLists.txt
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index 9dac69f..44f810e 100644
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--- a/CMakeLists.txt
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+++ b/CMakeLists.txt
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@@ -107,6 +107,55 @@ endif()
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# This will set ${CMAKE_THREAD_LIBS_INIT} to the correct, OS-specific value.
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find_package(Threads REQUIRED)
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+
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+# Check for explicit link against libatomic
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+#
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+# Depending on the toolchain, linking a program using atomic functions may need
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+# "-latomic" explicitly passed to the linker
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+#
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+# This check first tests if atomics are available in the C-library, if not and
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+# libatomic exists, then it runs the same test with -latomic added to the
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+# linker flags.
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+
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+# Helper for checking for atomics
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+function(check_working_cxx_atomics varname additional_lib)
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+ include(CheckCXXSourceCompiles)
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+ include(CMakePushCheckState)
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+ cmake_push_check_state()
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+ set(CMAKE_REQUIRED_FLAGS "-std=c++11")
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+ set(CMAKE_REQUIRED_LIBRARIES "${additional_lib}")
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+ set(CMAKE_REQUIRED_QUIET 1)
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+ CHECK_CXX_SOURCE_COMPILES("
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+#include <atomic>
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+std::atomic<int> x;
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+int main() {
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+ return std::atomic_fetch_add_explicit(&x, 1, std::memory_order_seq_cst);
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+}
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+" ${varname})
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+ cmake_pop_check_state()
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+endfunction(check_working_cxx_atomics)
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+
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+# First check if atomics work without the library.
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+# If not, check if the library exists, and atomics work with it.
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+check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITHOUT_LIB "")
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+if(HAVE_CXX_ATOMICS_WITHOUT_LIB)
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+ message(STATUS "Atomics provided by the C-library - yes")
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+else()
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+ message(STATUS "Atomics provided by the C-library - no")
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+ find_library(LIBATOMIC_LIBRARY NAMES atomic PATH_SUFFIXES lib)
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+ if(LIBATOMIC_LIBRARY)
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+ check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITH_LIB "${LIBATOMIC_LIBRARY}")
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+ if (HAVE_CXX_ATOMICS_WITH_LIB)
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+ message(STATUS "Atomics provided by libatomic - yes")
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+ else()
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+ message(STATUS "Atomics provided by libatomic - no")
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+ message(FATAL_ERROR "Compiler must support std::atomic!")
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+ endif()
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+ else()
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+ message(FATAL_ERROR "Compiler appears to require libatomic, but cannot find it.")
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+ endif()
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+endif()
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+
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#===============================================================================
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#= System Introspection
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#-------------------------------------------------------------------------------
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@@ -387,6 +436,7 @@ set(PULSEVIEW_LINK_LIBS
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${Boost_LIBRARIES}
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${QT_LIBRARIES}
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${CMAKE_THREAD_LIBS_INIT}
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+ ${LIBATOMIC_LIBRARY}
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)
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if(STATIC_PKGDEPS_LIBS)
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--
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2.8.3
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