SERVER-79410 Enable bugprone-unused-return-value clang lint warning

.clang-tidy.in

@@ -25,6 +25,7 @@ Checks:          '-*,
                   bugprone-swapped-arguments,
                   bugprone-terminating-continue,
                   bugprone-undelegated-constructor,
+                  bugprone-unused-return-value,
                   hicpp-static-assert,
                   hicpp-undelegated-constructor,
                   misc-static-assert,
@@ -75,7 +76,6 @@ Checks:          '-*,
                   -bugprone-suspicious-missing-comma,
                   -bugprone-suspicious-semicolon,
                   -bugprone-undefined-memory-manipulation,
-                  -bugprone-unused-return-value,
                   -cert-err34-c,
                   -cert-err52-cpp,
                   -cert-err60-cpp,

src/mongo/crypto/jws_validator_openssl.cpp

@@ -120,13 +120,14 @@ public:
         uassertOpenSSL("Failed creating RSAKey", rsa.get() != nullptr);
         uassertOpenSSL("RSA key setup failed",
                        RSA_set0_key(rsa.get(), n.get(), e.get(), nullptr) == 1);
-        n.release();  // Now owned by rsa
-        e.release();  // Now owned by rsa
+        (void)n.release();  // Now owned by rsa, cast to void to explicitly ignore the return value.
+        (void)e.release();  // Now owned by rsa, cast to void to explicitly ignore the return value.
 
         uassertOpenSSL("Failed creating EVP_PKey", _key.get() != nullptr);
         uassertOpenSSL("EVP_PKEY assignment failed",
                        EVP_PKEY_assign_RSA(_key.get(), rsa.get()) == 1);
-        rsa.release();  // Now owned by _key
+        (void)rsa
+            .release();  // Now owned by _key, cast to void to explicitly ignore the return value.
     }
 
     Status validate(StringData algorithm, StringData payload, StringData signature) const final {

src/mongo/db/cursor_manager.cpp

@@ -283,8 +283,8 @@ void CursorManager::unpin(OperationContext* opCtx,
     }
 
     // The cursor will stay around in '_cursorMap', so release the unique pointer to avoid deleting
-    // it.
-    cursor.release();
+    // it. Cast to void to explicitly ignore the return value.
+    (void)cursor.release();
 }
 
 void CursorManager::appendActiveSessions(LogicalSessionIdSet* lsids) const {

src/mongo/transport/service_executor_utils.cpp

@@ -148,7 +148,9 @@ Status launchServiceWorkerThread(unique_function<void()> task) {
                                 "error"_attr = errorMessage(ec));
         }
 
-        ctx.release();
+        // The spawned thread takes over ownership, cast to void to explicitly ignore the return
+        // value.
+        (void)ctx.release();
 #endif
 
     } catch (const std::exception& e) {

src/mongo/util/net/ssl_manager_openssl.cpp

@@ -1700,9 +1700,10 @@ UniqueDHParams makeDefaultDHParameters() {
         return nullptr;
     }
 
-    // DH takes over memory management responsibilities after successfully setting these
-    p.release();
-    g.release();
+    // DH takes over memory management responsibilities after successfully setting these.
+    // Cast to void to explicitly ignore the return value.
+    (void)p.release();
+    (void)g.release();
 
     return dhparams;
 }