test=develop, add log message in the function UpdateDllFlag (#24937)

* test=develop, add log message in the function UpdateDllFlag

* test=develop, add the test

paddle/fluid/inference/api/api.cc

@@ -120,12 +120,19 @@ std::string get_version() {
   return ss.str();
 }
 
-#if defined(_WIN32) && defined(PADDLE_ON_INFERENCE)
-
 std::string UpdateDllFlag(const char *name, const char *value) {
-  return google::SetCommandLineOption(name, value);
+  std::string ret;
+  LOG(WARNING)
+      << "The function \"UpdateDllFlag\" is only used to update the flag "
+         "on the Windows shared library";
+  ret = google::SetCommandLineOption(name, value);
+
+  PADDLE_ENFORCE_EQ(
+      ret.empty(), false,
+      platform::errors::InvalidArgument(
+          "Fail to update flag: %s, please make sure the flag exists.", name));
+  LOG(INFO) << ret;
+  return ret;
 }
 
-#endif
-
 }  // namespace paddle

paddle/fluid/inference/api/api_tester.cc

@@ -14,6 +14,7 @@ limitations under the License. */
 
 #include <glog/logging.h>
 #include <gtest/gtest.h>
+#include <exception>
 #include "paddle/fluid/inference/api/paddle_inference_api.h"
 
 namespace paddle {
@@ -67,4 +68,12 @@ TEST(paddle_inference_api, get_version) {
   ASSERT_FALSE(version.empty());
 }
 
+TEST(paddle_inference_api, UpdateDllFlag) {
+  UpdateDllFlag("paddle_num_threads", "10");
+  try {
+    UpdateDllFlag("paddle_num_threads2", "10");
+  } catch (std::exception &e) {
+    LOG(INFO) << e.what();
+  }
+}
 }  // namespace paddle

paddle/fluid/inference/api/paddle_api.h

@@ -429,8 +429,6 @@ PD_INFER_DECL int PaddleDtypeSize(PaddleDType dtype);
 
 PD_INFER_DECL std::string get_version();
 
-#if defined(_WIN32) && defined(PADDLE_ON_INFERENCE)
 PD_INFER_DECL std::string UpdateDllFlag(const char* name, const char* value);
-#endif
 
 }  // namespace paddle