Add check for latomic

CMakeLists.txt

@@ -557,6 +557,23 @@ endif()
 # with clang
 set_property(TARGET strumpack PROPERTY POSITION_INDEPENDENT_CODE ON)
 
+
+# see https://github.com/pghysels/STRUMPACK/issues/82
+# TODO check if 32bit, check compiler??
+set(ATOMIC_TEST_SOURCE "#include <atomic>
+      int main() { std::atomic<int64_t> i(0); i++; return 0; }")
+check_cxx_source_compiles("${ATOMIC_TEST_SOURCE}" ATOMIC_INT64_IS_BUILTIN)
+if(NOT ATOMIC_INT64_IS_BUILTIN)
+  set(CMAKE_REQUIRED_LIBRARIES atomic)
+  check_cxx_source_compiles(
+    "${ATOMIC_TEST_SOURCE}" ATOMIC_INT64_REQUIRES_LIBATOMIC)
+  if (ATOMIC_INT64_REQUIRES_LIBATOMIC)
+    target_link_libraries(strumpack PRIVATE atomic)
+  endif()
+  unset(CMAKE_REQUIRED_LIBRARIES)
+endif()
+
+
 add_subdirectory(src)
 
 target_sources(strumpack