Restore _Atomic define before stdatomic.h for old gcc
see
@@ -649,12 +649,21 @@ int omp_get_num_procs(void);
__declspec(dllimport) int __cdecl omp_in_parallel(void);
__declspec(dllimport) int __cdecl omp_get_num_procs(void);
#endif
+
#if (__STDC_VERSION__ >= 201112L)
+#if defined(C_GCC) && ( __GNUC__ < 7)
+// workaround for GCC bug 65467
#ifndef _Atomic
#define _Atomic volatile
#endif
+#endif
#include <stdatomic.h>
+#else
+#ifndef _Atomic
+#define _Atomic volatile
#endif
+
+
#else
#ifdef __ELF__
int omp_in_parallel (void) __attribute__ ((weak));
