From b385d13f1f1b04c0ce86d9d05c6c3c25218c777f Mon Sep 17 00:00:00 2001 From: Samuel Martin Date: Fri, 27 May 2016 00:00:44 +0200 Subject: [PATCH] package/pulseview: fix build when linking against libatomic is needed 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 Cc: Romain Naour Cc: Thomas Petazzoni Signed-off-by: Samuel Martin Reviewed-by: Romain Naour Signed-off-by: Peter Korsgaard --- ...for-explicit-linking-against-libatom.patch | 117 ++++++++++++++++++ 1 file changed, 117 insertions(+) create mode 100644 package/pulseview/0002-cmake-add-check-for-explicit-linking-against-libatom.patch diff --git a/package/pulseview/0002-cmake-add-check-for-explicit-linking-against-libatom.patch b/package/pulseview/0002-cmake-add-check-for-explicit-linking-against-libatom.patch new file mode 100644 index 0000000000..70549e6d72 --- /dev/null +++ b/package/pulseview/0002-cmake-add-check-for-explicit-linking-against-libatom.patch @@ -0,0 +1,117 @@ +From 71830c804be76cf6abe913ac2fe584947b7a91ea Mon Sep 17 00:00:00 2001 +From: Samuel Martin +Date: Tue, 24 May 2016 23:08:40 +0200 +Subject: [PATCH] cmake: add check for explicit linking against libatomic + +To use atomics functions, some toolchains requires to explicitly add +-latomic to the linker flags (because they are not provided by libc, +but libatomic). + +This change adds a helper function trying to build/link a test program +using atomics, then calls it to: +* first check if atomics are directly available in the libc; +* if not and libatomic has been found, then run the same test with + "-latomic" added to the linker flags. +The pulseview link library list is updated according to the results of +these tests. + +This issue was triggered by the Buildroot farms: + http://autobuild.buildroot.org/results/1e3/1e3101261252d5f30fdf842cc99604e4f4c25eef/build-end.log + +Notes: +1- CMAKE_REQUIRED_* variables are only used in check functions. They + are not automatically forwarded to/handled by the target commands + (such as target_link_library), because the check functions are + implemented as macro in CMake code, whereas many target commands + are native. +2- Because of note #1, CMAKE_REQUIRED_LIBRARIES (or its value) must be + explicitly passed to the target_link_library command when this is + needed. +3- In this implementation, LIBATOMIC_LIBRARY is only set when it is + needed; so, unconditionally appending it to PULSEVIEW_LINK_LIBS + will produce the expected behavior. + +Signed-off-by: Samuel Martin + +--- +changes v1->v2: +- use std::atomic_fetch_add_explicit function instead of + __atomic_fetch_add_4; +- rework code using cmake_*_check_state and find_library helpers; +- quiet-ize checks and clean outputs +- extend the commit log +--- + CMakeLists.txt | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ + 1 file changed, 50 insertions(+) + +diff --git a/CMakeLists.txt b/CMakeLists.txt +index 9dac69f..44f810e 100644 +--- a/CMakeLists.txt ++++ b/CMakeLists.txt +@@ -107,6 +107,55 @@ endif() + # This will set ${CMAKE_THREAD_LIBS_INIT} to the correct, OS-specific value. + find_package(Threads REQUIRED) + ++ ++# Check for explicit link against libatomic ++# ++# Depending on the toolchain, linking a program using atomic functions may need ++# "-latomic" explicitly passed to the linker ++# ++# This check first tests if atomics are available in the C-library, if not and ++# libatomic exists, then it runs the same test with -latomic added to the ++# linker flags. ++ ++# Helper for checking for atomics ++function(check_working_cxx_atomics varname additional_lib) ++ include(CheckCXXSourceCompiles) ++ include(CMakePushCheckState) ++ cmake_push_check_state() ++ set(CMAKE_REQUIRED_FLAGS "-std=c++11") ++ set(CMAKE_REQUIRED_LIBRARIES "${additional_lib}") ++ set(CMAKE_REQUIRED_QUIET 1) ++ CHECK_CXX_SOURCE_COMPILES(" ++#include ++std::atomic x; ++int main() { ++ return std::atomic_fetch_add_explicit(&x, 1, std::memory_order_seq_cst); ++} ++" ${varname}) ++ cmake_pop_check_state() ++endfunction(check_working_cxx_atomics) ++ ++# First check if atomics work without the library. ++# If not, check if the library exists, and atomics work with it. ++check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITHOUT_LIB "") ++if(HAVE_CXX_ATOMICS_WITHOUT_LIB) ++ message(STATUS "Atomics provided by the C-library - yes") ++else() ++ message(STATUS "Atomics provided by the C-library - no") ++ find_library(LIBATOMIC_LIBRARY NAMES atomic PATH_SUFFIXES lib) ++ if(LIBATOMIC_LIBRARY) ++ check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITH_LIB "${LIBATOMIC_LIBRARY}") ++ if (HAVE_CXX_ATOMICS_WITH_LIB) ++ message(STATUS "Atomics provided by libatomic - yes") ++ else() ++ message(STATUS "Atomics provided by libatomic - no") ++ message(FATAL_ERROR "Compiler must support std::atomic!") ++ endif() ++ else() ++ message(FATAL_ERROR "Compiler appears to require libatomic, but cannot find it.") ++ endif() ++endif() ++ + #=============================================================================== + #= System Introspection + #------------------------------------------------------------------------------- +@@ -387,6 +436,7 @@ set(PULSEVIEW_LINK_LIBS + ${Boost_LIBRARIES} + ${QT_LIBRARIES} + ${CMAKE_THREAD_LIBS_INIT} ++ ${LIBATOMIC_LIBRARY} + ) + + if(STATIC_PKGDEPS_LIBS) +-- +2.8.3 +