[lldb] Implement priority system for symbol locator plugin

Author: George Hu

lldb/include/lldb/Core/PluginManager.h

@@ -431,7 +431,8 @@ class PluginManager {
       SymbolLocatorDownloadObjectAndSymbolFile download_object_symbol_file =
           nullptr,
       SymbolLocatorFindSymbolFileInBundle find_symbol_file_in_bundle = nullptr,
-      DebuggerInitializeCallback debugger_init_callback = nullptr);
+      DebuggerInitializeCallback debugger_init_callback = nullptr,
+      SymbolLocatorGetPriority get_priority_callback = nullptr);
 
   static bool UnregisterPlugin(SymbolLocatorCreateInstance create_callback);
 

lldb/include/lldb/Symbol/SymbolLocator.h

@@ -14,6 +14,9 @@
 
 namespace lldb_private {
 
+// Default priority for symbol locator plugins. Lower values are favored first.
+static constexpr uint32_t kDefaultSymbolLocatorPriority = 2;
+
 class SymbolLocator : public PluginInterface {
 public:
   SymbolLocator() = default;

lldb/include/lldb/lldb-private-interfaces.h

@@ -100,6 +100,7 @@ typedef std::optional<FileSpec> (*SymbolLocatorLocateExecutableSymbolFile)(
 typedef bool (*SymbolLocatorDownloadObjectAndSymbolFile)(
     ModuleSpec &module_spec, Status &error, bool force_lookup,
     bool copy_executable);
+typedef uint64_t (*SymbolLocatorGetPriority)();
 using BreakpointHitCallback =
     std::function<bool(void *baton, StoppointCallbackContext *context,
                        lldb::user_id_t break_id, lldb::user_id_t break_loc_id)>;

lldb/source/Core/PluginManager.cpp

@@ -13,6 +13,7 @@
 #include "lldb/Host/HostInfo.h"
 #include "lldb/Interpreter/OptionValueProperties.h"
 #include "lldb/Symbol/SaveCoreOptions.h"
+#include "lldb/Symbol/SymbolLocator.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Utility/FileSpec.h"
 #include "lldb/Utility/Status.h"
@@ -25,6 +26,7 @@
 #include <map>
 #include <memory>
 #include <mutex>
+#include <queue>
 #include <string>
 #include <utility>
 #include <vector>
@@ -323,6 +325,29 @@ template <typename Instance> class PluginInstances {
     return enabled_instances;
   }
 
+  // Return a priority queue of all enabled instances, ordered by priority
+  // (lower priority values = higher priority in queue)
+  template <typename PriorityGetter>
+  std::priority_queue<Instance, std::vector<Instance>,
+                      std::function<bool(const Instance &, const Instance &)>>
+  GetPriorityQueue(PriorityGetter get_priority) {
+    // Create comparator that orders by priority (lower values = higher
+    // priority)
+    auto comparator = [get_priority](const Instance &a, const Instance &b) {
+      return get_priority(a) > get_priority(b); // Reverse for min-heap behavior
+    };
+
+    std::priority_queue<Instance, std::vector<Instance>,
+                        std::function<bool(const Instance &, const Instance &)>>
+        pq(comparator);
+
+    for (const auto &instance : m_instances) {
+      if (instance.enabled)
+        pq.push(instance);
+    }
+    return pq;
+  }
+
   const Instance *GetInstanceAtIndex(uint32_t idx) {
     uint32_t count = 0;
 
@@ -1223,18 +1248,26 @@ struct SymbolLocatorInstance
       SymbolLocatorLocateExecutableSymbolFile locate_executable_symbol_file,
       SymbolLocatorDownloadObjectAndSymbolFile download_object_symbol_file,
       SymbolLocatorFindSymbolFileInBundle find_symbol_file_in_bundle,
-      DebuggerInitializeCallback debugger_init_callback)
+      DebuggerInitializeCallback debugger_init_callback,
+      SymbolLocatorGetPriority get_priority_callback)
       : PluginInstance<SymbolLocatorCreateInstance>(
             name, description, create_callback, debugger_init_callback),
         locate_executable_object_file(locate_executable_object_file),
         locate_executable_symbol_file(locate_executable_symbol_file),
         download_object_symbol_file(download_object_symbol_file),
-        find_symbol_file_in_bundle(find_symbol_file_in_bundle) {}
+        find_symbol_file_in_bundle(find_symbol_file_in_bundle),
+        get_priority_callback(get_priority_callback) {}
+
+  uint64_t GetPriority() const {
+    return get_priority_callback ? get_priority_callback()
+                                 : kDefaultSymbolLocatorPriority;
+  }
 
   SymbolLocatorLocateExecutableObjectFile locate_executable_object_file;
   SymbolLocatorLocateExecutableSymbolFile locate_executable_symbol_file;
   SymbolLocatorDownloadObjectAndSymbolFile download_object_symbol_file;
   SymbolLocatorFindSymbolFileInBundle find_symbol_file_in_bundle;
+  SymbolLocatorGetPriority get_priority_callback;
 };
 typedef PluginInstances<SymbolLocatorInstance> SymbolLocatorInstances;
 
@@ -1250,11 +1283,13 @@ bool PluginManager::RegisterPlugin(
     SymbolLocatorLocateExecutableSymbolFile locate_executable_symbol_file,
     SymbolLocatorDownloadObjectAndSymbolFile download_object_symbol_file,
     SymbolLocatorFindSymbolFileInBundle find_symbol_file_in_bundle,
-    DebuggerInitializeCallback debugger_init_callback) {
+    DebuggerInitializeCallback debugger_init_callback,
+    SymbolLocatorGetPriority get_priority_callback) {
   return GetSymbolLocatorInstances().RegisterPlugin(
       name, description, create_callback, locate_executable_object_file,
       locate_executable_symbol_file, download_object_symbol_file,
-      find_symbol_file_in_bundle, debugger_init_callback);
+      find_symbol_file_in_bundle, debugger_init_callback,
+      get_priority_callback);
 }
 
 bool PluginManager::UnregisterPlugin(
@@ -1270,8 +1305,13 @@ PluginManager::GetSymbolLocatorCreateCallbackAtIndex(uint32_t idx) {
 ModuleSpec
 PluginManager::LocateExecutableObjectFile(const ModuleSpec &module_spec,
                                           StatisticsMap &map) {
-  auto instances = GetSymbolLocatorInstances().GetSnapshot();
-  for (auto &instance : instances) {
+  auto pq = GetSymbolLocatorInstances().GetPriorityQueue(
+      [](const auto &instance) { return instance.GetPriority(); });
+
+  while (!pq.empty()) {
+    auto instance = pq.top();
+    pq.pop();
+
     if (instance.locate_executable_object_file) {
       StatsDuration time;
       std::optional<ModuleSpec> result;
@@ -1290,8 +1330,12 @@ PluginManager::LocateExecutableObjectFile(const ModuleSpec &module_spec,
 FileSpec PluginManager::LocateExecutableSymbolFile(
     const ModuleSpec &module_spec, const FileSpecList &default_search_paths,
     StatisticsMap &map) {
-  auto instances = GetSymbolLocatorInstances().GetSnapshot();
-  for (auto &instance : instances) {
+  auto pq = GetSymbolLocatorInstances().GetPriorityQueue(
+      [](const auto &instance) { return instance.GetPriority(); });
+
+  while (!pq.empty()) {
+    auto instance = pq.top();
+    pq.pop();
     if (instance.locate_executable_symbol_file) {
       StatsDuration time;
       std::optional<FileSpec> result;

lldb/source/Plugins/SymbolLocator/Debuginfod/SymbolLocatorDebuginfod.cpp

@@ -83,6 +83,16 @@ class PluginProperties : public Properties {
     }
   }
 
+  uint32_t GetPriority() const {
+    std::optional<uint32_t> priority =
+        m_collection_sp->GetPropertyAtIndexAs<uint64_t>(ePropertyPriority);
+    if (priority && *priority >= 0) {
+      return priority.value();
+    } else {
+      return kDefaultSymbolLocatorPriority;
+    }
+  }
+
 private:
   void ServerURLsChangedCallback() {
     m_server_urls = GetDebugInfoDURLs();
@@ -103,6 +113,13 @@ static PluginProperties &GetGlobalPluginProperties() {
   return g_settings;
 }
 
+static uint64_t GetDebuginfodPriority() {
+  // Grab LLDB's Debuginfod overrides from the
+  // plugin.symbol-locator.debuginfod.* settings.
+  PluginProperties &plugin_props = GetGlobalPluginProperties();
+  return plugin_props.GetPriority();
+}
+
 SymbolLocatorDebuginfod::SymbolLocatorDebuginfod() : SymbolLocator() {}
 
 void SymbolLocatorDebuginfod::Initialize() {
@@ -112,7 +129,8 @@ void SymbolLocatorDebuginfod::Initialize() {
     PluginManager::RegisterPlugin(
         GetPluginNameStatic(), GetPluginDescriptionStatic(), CreateInstance,
         LocateExecutableObjectFile, LocateExecutableSymbolFile, nullptr,
-        nullptr, SymbolLocatorDebuginfod::DebuggerInitialize);
+        nullptr, SymbolLocatorDebuginfod::DebuggerInitialize,
+        GetDebuginfodPriority);
     llvm::HTTPClient::initialize();
   });
 }

lldb/source/Plugins/SymbolLocator/Debuginfod/SymbolLocatorDebuginfodProperties.td

@@ -10,4 +10,7 @@ let Definition = "symbollocatordebuginfod" in {
   def Timeout : Property<"timeout", "UInt64">,
     DefaultUnsignedValue<0>,
     Desc<"Timeout (in seconds) for requests made to a DEBUGINFOD server. A value of zero means we use the debuginfod default timeout: DEBUGINFOD_TIMEOUT if the environment variable is set and 90 seconds otherwise.">;
+  def Priority : Property<"priority", "UInt64">,
+    DefaultUnsignedValue<2>,
+    Desc<"The priority order for this symbol locator plugin when multiple symbol locators are available. Lower values indicate higher priority. The default symbol locator priority is 2">;
 }