config: check for libatomic. Fixes #90.

config/config.py

@@ -784,6 +784,26 @@ def gpu_blas():
         print_warn( 'No GPU BLAS library found' )
 # end
 
+#-------------------------------------------------------------------------------
+def require_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/require_libatomic.cc' )
+    print_result( 'x', rc )
+    if (rc != 0):
+        print_test( 'std::atomic requires -latomic' )
+        env = {'LIBS': '-latomic'}
+        (rc, out, err) = compile_exe( 'config/require_libatomic.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/require_libatomic.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

@@ -56,6 +56,7 @@ def main():
    #config.prog_cxx_flag( '-Wmissing-declarations' )
    #config.prog_cxx_flag( '-Wconversion' )
    #config.prog_cxx_flag( '-Werror' )
+    config.require_libatomic()
 
     config.openmp()