Add pg_nodiscard function declaration specifier

petere · petere · commit c617aea6acdd · 2020-11-11T11:00:27.000+01:00
pg_nodiscard means the compiler should warn if the result of a function call is ignored. The name "nodiscard" is chosen in alignment with (possibly future) C and C++ standards. It maps to the GCC attribute warn_unused_result. Reviewed-by: Michael Paquier <michael@paquier.xyz> Discussion: https://www.postgresql.org/message-id/flat/e3753562-99cd-b65f-5aca-687dfd1ec2fc@2ndquadrant.com
diff --git a/src/include/c.h b/src/include/c.h
@@ -111,6 +111,18 @@
 #define pg_attribute_unused()
 #endif
 
+/*
+ * pg_nodiscard means the compiler should warn if the result of a function
+ * call is ignored.  The name "nodiscard" is chosen in alignment with
+ * (possibly future) C and C++ standards.  For maximum compatibility, use it
+ * as a function declaration specifier, so it goes before the return type.
+ */
+#ifdef __GNUC__
+#define pg_nodiscard __attribute__((warn_unused_result))
+#else
+#define pg_nodiscard
+#endif
+
 /*
  * Append PG_USED_FOR_ASSERTS_ONLY to definitions of variables that are only
  * used in assert-enabled builds, to avoid compiler warnings about unused
