This patch adds a wrapper macro __rte_warn_unused_result for the
warn_unused_result function attribute.
Marking a function __rte_warn_unused_result will make the compiler
emit a warning in case the caller does not use the function's return
value.
Changes since RFC:
* Include usage recommendation and GCC peculiarities in the macro
documentation.
Acked-by: Bruce Richardson <bruce.richard...@intel.com>
Signed-off-by: Mattias Rönnblom <mattias.ronnb...@ericsson.com>
---
lib/eal/include/rte_common.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/lib/eal/include/rte_common.h b/lib/eal/include/rte_common.h
index 4a399cc7c8..67587025ab 100644
--- a/lib/eal/include/rte_common.h
+++ b/lib/eal/include/rte_common.h
@@ -222,6 +222,31 @@ static void __attribute__((destructor(RTE_PRIO(prio)),
used)) func(void)
*/
#define __rte_noreturn __attribute__((noreturn))
+/**
+ * Issue a warning in case the function's return value is ignored.
+ *
+ * The use of this attribute should be restricted to cases where
+ * ignoring the marked function's return value is almost always a
+ * bug. With GCC, some effort is required to make clear that ignoring
+ * the return value is intentional. The usual void-casting method to
+ * mark something unused as used does not suppress the warning with
+ * this compiler.
+ *
+ * @code{.c}
+ * __rte_warn_unused_result int foo();
+ *
+ * void ignore_foo_result(void) {
+ * foo(); // generates a warning with all compilers
+ *
+ * (void)foo(); // still generates the warning with GCC (but not clang)
+ *
+ * int unused __rte_unused;
+ * unused = foo(); // does the trick with all compilers
+ * }
+ * @endcode
+ */
+#define __rte_warn_unused_result __attribute__((warn_unused_result))
+
/**
* Force a function to be inlined
*/
--
2.25.1
