Merge pull request #14858 from charris/backport-14827

BLD: Prevent -flto from optimising long double representation check away

numpy/core/setup_common.py

@@ -265,8 +265,9 @@ def check_long_double_representation(cmd):
     except ValueError:
         # try linking to support CC="gcc -flto" or icc -ipo
         # struct needs to be volatile so it isn't optimized away
+        # additionally "clang -flto" requires the foo struct to be used
         body = body.replace('struct', 'volatile struct')
-        body += "int main(void) { return 0; }\n"
+        body += "int main(void) { return foo.before[0]; }\n"
         src, obj = cmd._compile(body, None, None, 'c')
         cmd.temp_files.append("_configtest")
         cmd.compiler.link_executable([obj], "_configtest")