From 547475295a9bb2aca6f06074caa93a08f6625691 Mon Sep 17 00:00:00 2001
From: michael-grunder <michael.grunder@gmail.com>
Date: Sun, 5 Oct 2025 21:26:26 -0700
Subject: [PATCH] Introduce "must use attribute"

Conditionally add `[[nodiscard]]` (c23) or
`__attribute__((warn_unused_result))` when the compiler supports it.

This commit initially just adds iit to `cluster_map_keyspace` but we can
go throughour API adding it where appropriate.
---
 cluster_library.h |  2 +-
 common.h          | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/cluster_library.h b/cluster_library.h
index 731ec03..361a1e5 100644
--- a/cluster_library.h
+++ b/cluster_library.h
@@ -378,7 +378,7 @@ PHP_REDIS_API redisCluster *cluster_create(double timeout, double read_timeout,
     int failover, int persistent);
 PHP_REDIS_API void cluster_free(redisCluster *c, int free_ctx);
 PHP_REDIS_API void cluster_init_seeds(redisCluster *c, zend_string **seeds, uint32_t nseeds);
-PHP_REDIS_API int cluster_map_keyspace(redisCluster *c);
+REDIS_NODISCARD PHP_REDIS_API int cluster_map_keyspace(redisCluster *c);
 PHP_REDIS_API void cluster_free_node(redisClusterNode *node);
 
 /* Functions for interacting with cached slots maps */
diff --git a/common.h b/common.h
index 559e4a2..8936c8e 100644
--- a/common.h
+++ b/common.h
@@ -41,6 +41,31 @@
 # error "Unknown endianness"
 #endif
 
+#if defined(_MSC_VER) && !defined(__clang__)
+#  define REDIS_MSVC 1
+#endif
+
+#ifndef REDIS_MSVC
+#  if defined(__has_c_attribute)
+#    if __has_c_attribute(nodiscard)
+#      define REDIS_NODISCARD [[nodiscard]]
+#    endif
+#  endif
+#  ifndef REDIS_NODISCARD
+#    if defined(__has_attribute)
+#      if __has_attribute(warn_unused_result)
+#        define REDIS_NODISCARD __attribute__((warn_unused_result))
+#      endif
+#    elif defined(__GNUC__) || defined(__clang__)
+#      define REDIS_NODISCARD __attribute__((warn_unused_result))
+#    else
+#      define REDIS_NODISCARD
+#    endif
+#  endif
+#else
+#  define REDIS_NODISCARD
+#endif
+
 #include "backoff.h"
 
 typedef enum {