config: check for libatomic. Fixes #90.

CMakeLists.txt

@@ -61,6 +61,7 @@ set_property( CACHE gpu_backend PROPERTY STRINGS
 
 # After color.
 include( "cmake/util.cmake" )
+include( "cmake/config.cmake" )
 
 # Recognize CTest's BUILD_TESTING flag. (Quotes required.)
 if (NOT "${BUILD_TESTING}" STREQUAL "")
@@ -357,7 +358,6 @@ endif()
 
 #-------------------------------------------------------------------------------
 # Clean stale defines.h from Makefile-based build.
-message( "" )
 file( REMOVE "${CMAKE_CURRENT_SOURCE_DIR}/include/blas/defines.h" )
 
 # Include directory.
@@ -371,6 +371,8 @@ target_include_directories(
 )
 
 # OpenMP support.
+message( "" )
+message( STATUS "${bold}Looking for OpenMP${not_bold}" )
 set( openmp_lib "" )
 set( blaspp_use_openmp false )  # output in blasppConfig.cmake.in
 if (NOT use_openmp)
@@ -384,7 +386,15 @@ else()
     endif()
 endif()
 
+# If -latomic is required, add as link library to blaspp.
+message( "" )
+check_libatomic()
+if (libatomic_required)
+    target_link_libraries( blaspp PUBLIC "-latomic" )
+endif()
+
 # Get git commit id.
+message( "" )
 if (EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/.git")
     execute_process( COMMAND git rev-parse --short HEAD
                      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}

config/config.py

@@ -784,6 +784,26 @@ def gpu_blas():
         print_warn( 'No GPU BLAS library found' )
 # end
 
+#-------------------------------------------------------------------------------
+def libatomic():
+    '''
+    Tests whether using `std::atomic` requires linking with `-latomic`
+    for 64-bit values, which is the case on some 32-bit systems.
+    '''
+    print_test( 'std::atomic links without -latomic' )
+    (rc, out, err) = compile_exe( 'config/std_atomic.cc' )
+    print_result( 'x', rc )
+    if (rc != 0):
+        print_test( 'std::atomic requires -latomic' )
+        env = {'LIBS': '-latomic'}
+        (rc, out, err) = compile_exe( 'config/std_atomic.cc', env )
+        print_result( 'x', rc )
+        if (rc == 0):
+            environ.merge( env )
+        else:
+            raise Error( 'cannot compile libatomic test' )
+# end
+
 #-------------------------------------------------------------------------------
 def get_package( name, directories, repo_url, tar_url, tar_filename ):
     '''

config/std_atomic.cc

@@ -0,0 +1,11 @@
+#include <atomic>
+#include <cstdint>
+
+int main( int argc, char** argv )
+{
+    std::atomic<std::int64_t> x = 0;
+    for (int i = 1; i < argc; ++i) {
+        ++x;
+    }
+    return x;
+}

configure.py

@@ -57,6 +57,9 @@ def main():
    #config.prog_cxx_flag( '-Wconversion' )
    #config.prog_cxx_flag( '-Werror' )
 
+    print_header( 'Libraries' )
+    config.libatomic()
+
     config.openmp()
 
     config.lapack.blas()