GNU-style attributes: disable on z/OS as well like on windows; factor

src/platform_disable_attributes.h

@@ -0,0 +1,18 @@
+#ifndef PLATFORM_DISABLE_ATTRIBUTES_H
+#define PLATFORM_DISABLE_ATTRIBUTES_H
+
+/* Disable GNU-style attributes
+   (https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html ), turning them
+   into noops.  This lets the code compile with compilers not supporting
+   attributes, while keeping them enabled when they matter.
+
+   This header is included by platform-specific code where needed: it is not
+   for the user to directly see. */
+
+/* Notice that this definition is extremely conservative: supporting exactly
+   one argument would suffice. */
+#define __attribute__(...) /* nothing */
+#define attribute __attribute__
+
+
+#endif // #ifndef PLATFORM_DISABLE_ATTRIBUTES_H

src/platform_windows.h

@@ -9,20 +9,15 @@
 
 // Windows platform specifica
 
-// The windows compiler used by default does not support GNU-style attributes;
-// let us just disable them altogether with a CPP defintition, so that
-// attributes become no-ops on windows but keep functioning on the other
-// platforms.
-// Notice that this definition is extremely conservative: supporting exactly
-// one argument would suffice.
-#define __attribute__(...) /* nothing */
-#define attribute __attribute__
-
 #ifndef _EXPORT_PEP_ENGINE_DLL
 #define _EXPORT_PEP_ENGINE_DLL
 #endif
 #pragma warning(disable : 4996)
 
+// The compiler used by default on this platform does not support GNU-style
+// attributes.
+#include "platform_disable_attributes.h"
+
 // We need to make sure winsock2 is included before windows.h, or we will get redefinitions of symbols
 // as windows.h includes winsock1.h, so we will have duplicate symbols if windows.h is included first.
 // It seems some of our code includes sync.h before including winsock.h, leading to the failure.

src/platform_zos.h

@@ -11,6 +11,10 @@
 # error "this header should only ever be included on z/OS"
 #endif
 
+// The compiler used by default on this platform does not support GNU-style
+// attributes.
+#include "platform_disable_attributes.h"
+
 /* Workaround standard header problems. */
 
 #ifdef __cplusplus