Print NVML return code as string

src/loaders/loader_nvml.cpp

@@ -161,6 +161,19 @@ bool libnvml_loader::Load(const std::string& library_name) {
     return false;
   }
 
+#if defined(LIBRARY_LOADER_NVML_H_DLOPEN)
+  nvmlErrorString =
+      reinterpret_cast<decltype(this->nvmlErrorString)>(
+          dlsym(library_, "nvmlErrorString"));
+#endif
+#if defined(LIBRARY_LOADER_NVML_H_DT_NEEDED)
+  nvmlErrorString = &::nvmlErrorString;
+#endif
+  if (!nvmlErrorString) {
+    CleanUp(true);
+    return false;
+  }
+
   loaded_ = true;
   return true;
 }

src/loaders/loader_nvml.h

@@ -31,6 +31,7 @@ class libnvml_loader {
   decltype(&::nvmlDeviceGetHandleByPciBusId_v2) nvmlDeviceGetHandleByPciBusId_v2;
   decltype(&::nvmlDeviceGetMemoryInfo) nvmlDeviceGetMemoryInfo;
   decltype(&::nvmlDeviceGetClockInfo) nvmlDeviceGetClockInfo;
+  decltype(&::nvmlErrorString) nvmlErrorString;
 
  private:
   void CleanUp(bool unload);

src/nvml.cpp

@@ -22,10 +22,14 @@ bool checkNVML(const char* pciBusId){
                 ret = nvml.nvmlDeviceGetHandleByPciBusId(pciBusId, &nvidiaDevice);
 
             if (ret != NVML_SUCCESS) {
-                std::cerr << "MANGOHUD: Getting handle by PCI bus ID failed! Using index 0.\n";
+                std::cerr << "MANGOHUD: Getting device handle by PCI bus ID failed: " << nvml.nvmlErrorString(ret) << "\n";
+                std::cerr << "          Using index 0.\n";
                 ret = nvml.nvmlDeviceGetHandleByIndex(0, &nvidiaDevice);
             }
 
+            if (ret != NVML_SUCCESS)
+                std::cerr << "MANGOHUD: Getting device handle failed: " << nvml.nvmlErrorString(ret) << "\n";
+
             nvmlSuccess = (ret == NVML_SUCCESS);
             return nvmlSuccess;
         }