Bug#33086882: USE NODISCARD INSTEAD OF WARN_UNUSED_RESULT

Use the standard [[nodiscard]] attribute instead of
MY_ATTRIBUTE((warn_unused_result)), which is only understood by GCC
and clang.

Change-Id: I4e43de3aad428c84d9f87c54b65ba82063d8ef92

Author: kahatlen

include/priority_queue.h

@@ -33,8 +33,6 @@
 #include <utility>
 #include <vector>
 
-#include "my_compiler.h"
-
 #include "template_utils.h"
 
 #if defined(EXTRA_CODE_FOR_UNIT_TESTING)
@@ -392,8 +390,7 @@ class Priority_queue : public Less {
     @param  n number of elements.
     @retval true if out-of-memory, false otherwise.
   */
-  MY_ATTRIBUTE((warn_unused_result))
-  bool reserve(size_type n) {
+  [[nodiscard]] bool reserve(size_type n) {
     assert(n <= m_container.max_size());
     try {
       m_container.reserve(n);

router/src/harness/include/mysql/harness/stdx/attribute.h

@@ -45,13 +45,4 @@
 #define STDX_NONNULL
 #endif
 
-// STDX_NODISCARD
-#if __has_cpp_attribute(nodiscard)
-#define STDX_NODISCARD [[nodiscard]]
-#elif __has_cpp_attribute(gnu::warn_unused_result)
-#define STDX_NODISCARD [[gnu::warn_unused_result]]
-#else
-#define STDX_NODISCARD
-#endif
-
 #endif

router/tests/helpers/router_component_test.h

@@ -63,10 +63,9 @@ class RouterComponentTest : public ProcessManager, public ::testing::Test {
    * @return bool value indicating if the pattern was found in the log file or
    * not
    */
-  STDX_NODISCARD
-  bool wait_log_contains(const ProcessWrapper &process,
-                         const std::string &pattern,
-                         std::chrono::milliseconds timeout);
+  [[nodiscard]] bool wait_log_contains(const ProcessWrapper &process,
+                                       const std::string &pattern,
+                                       std::chrono::milliseconds timeout);
 
   /** @brief Sleep for a duration given as a parameter. The duration is
    * increased 10 times for the run with VALGRIND.

router/tests/helpers/router_test_helpers.h

@@ -174,8 +174,7 @@ void init_windows_sockets();
  *
  * @returns true if the selected port accepts connections, false otherwise
  */
-STDX_NODISCARD
-bool wait_for_port_ready(
+[[nodiscard]] bool wait_for_port_ready(
     uint16_t port, std::chrono::milliseconds timeout = kDefaultPortReadyTimeout,
     const std::string &hostname = "127.0.0.1");
 
@@ -185,8 +184,7 @@ bool wait_for_port_ready(
  *
  * @returns true if the selected port is available, false otherwise
  */
-STDX_NODISCARD
-bool is_port_available(const uint16_t port);
+[[nodiscard]] bool is_port_available(const uint16_t port);
 
 /**
  * Wait until the port is not available (is used by any application).
@@ -197,8 +195,7 @@ bool is_port_available(const uint16_t port);
  * @return false if the port is still available after the timeout expiry,
  *         true otherwise.
  */
-STDX_NODISCARD
-bool wait_for_port_not_available(
+[[nodiscard]] bool wait_for_port_not_available(
     const uint16_t port,
     std::chrono::milliseconds timeout = std::chrono::seconds(10));
 
@@ -211,8 +208,7 @@ bool wait_for_port_not_available(
  * @return false if the port is still not available after the timeout expiry,
  *         true otherwise.
  */
-STDX_NODISCARD
-bool wait_for_port_available(
+[[nodiscard]] bool wait_for_port_available(
     const uint16_t port,
     std::chrono::milliseconds timeout = std::chrono::seconds(10));