[Lldb-commits] [lldb] [lldb] Let callers of GetSharedModule skip symbol locating (NFC) (PR #214829)

[Jonas Devlieghere via lldb-commits]

https://github.com/JDevlieghere created https://github.com/llvm/llvm-project/pull/214829

GetSharedModule falls back on the symbol locator plugins when the spec does not already name a binary it can open, and it does so while holding the global module list lock. Locating a binary or symbol file can potentially be quite slow, so we should have the option to opt out of that, for example, if we already did the search upfront.

>From 5e4fe84b93494676ec6172330218d58e913071af Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas at devlieghere.com>
Date: Thu, 6 Aug 2026 22:10:40 -0700
Subject: [PATCH] [lldb] Let callers of GetSharedModule skip symbol locating
 (NFC)

GetSharedModule falls back on the symbol locator plugins when the spec
does not already name a binary it can open, and it does so while holding
the global module list lock. Locating a binary or symbol file can
potentially be quite slow, so we should have the option to opt out of
that, for example, if we already did the search upfront.
---
 lldb/include/lldb/Core/ModuleList.h    |  3 +-
 lldb/source/Core/ModuleList.cpp        | 18 ++++++--
 lldb/unittests/Core/ModuleListTest.cpp | 60 ++++++++++++++++++++++++++
 3 files changed, 76 insertions(+), 5 deletions(-)

diff --git a/lldb/include/lldb/Core/ModuleList.h b/lldb/include/lldb/Core/ModuleList.h
index bea88a6cf1f51..aa0e7c674c1d2 100644
--- a/lldb/include/lldb/Core/ModuleList.h
+++ b/lldb/include/lldb/Core/ModuleList.h
@@ -497,7 +497,8 @@ class ModuleList {
   static Status
   GetSharedModule(const ModuleSpec &module_spec, lldb::ModuleSP &module_sp,
                   llvm::SmallVectorImpl<lldb::ModuleSP> *old_modules,
-                  bool *did_create_ptr, bool invoke_locate_callback = true);
+                  bool *did_create_ptr, bool invoke_locate_callback = true,
+                  bool invoke_symbol_locators = true);
 
   static bool RemoveSharedModule(lldb::ModuleSP &module_sp);
 
diff --git a/lldb/source/Core/ModuleList.cpp b/lldb/source/Core/ModuleList.cpp
index 88ddc62407bb4..4f81d8db7198d 100644
--- a/lldb/source/Core/ModuleList.cpp
+++ b/lldb/source/Core/ModuleList.cpp
@@ -1053,7 +1053,8 @@ size_t ModuleList::RemoveOrphanSharedModules(bool mandatory) {
 Status
 ModuleList::GetSharedModule(const ModuleSpec &module_spec, ModuleSP &module_sp,
                             llvm::SmallVectorImpl<lldb::ModuleSP> *old_modules,
-                            bool *did_create_ptr, bool invoke_locate_callback) {
+                            bool *did_create_ptr, bool invoke_locate_callback,
+                            bool invoke_symbol_locators) {
   SharedModuleList &shared_module_list = GetSharedModuleList();
   std::lock_guard<std::recursive_mutex> guard(shared_module_list.GetMutex());
   char path[PATH_MAX];
@@ -1203,9 +1204,18 @@ ModuleList::GetSharedModule(const ModuleSpec &module_spec, ModuleSP &module_sp,
     }
   }
 
-  // Either the file didn't exist where at the path, or no path was given, so
-  // we now have to use more extreme measures to try and find the appropriate
-  // module.
+  // Either the file didn't exist where at the path, or no path was given, so we
+  // now either have to use more extreme measures to try and find the
+  // appropriate module or end our search here.
+  if (!invoke_symbol_locators) {
+    std::string uuid_str;
+    if (uuid_ptr && uuid_ptr->IsValid())
+      uuid_str = uuid_ptr->GetAsString();
+    if (!uuid_str.empty())
+      return Status::FromErrorStringWithFormatv(
+          "cannot locate module for UUID '{}'", uuid_str);
+    return Status::FromErrorString("cannot locate module");
+  }
 
   // Fixup the incoming path in case the path points to a valid file, yet the
   // arch or UUID (if one was passed in) don't match.
diff --git a/lldb/unittests/Core/ModuleListTest.cpp b/lldb/unittests/Core/ModuleListTest.cpp
index b4747b7987059..399036ca64c5a 100644
--- a/lldb/unittests/Core/ModuleListTest.cpp
+++ b/lldb/unittests/Core/ModuleListTest.cpp
@@ -11,7 +11,9 @@
 #include "TestingSupport/TestUtilities.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Core/ModuleSpec.h"
+#include "lldb/Core/PluginManager.h"
 #include "lldb/Host/FileSystem.h"
+#include "lldb/Symbol/SymbolLocator.h"
 #include "lldb/Utility/ArchSpec.h"
 #include "lldb/Utility/UUID.h"
 
@@ -173,3 +175,61 @@ TEST(ModuleListTest, GetSharedModuleByUUIDIgnoresPath) {
     }
   }
 }
+
+// A symbol locator that records whether it was asked to find anything. It never
+// finds a binary, so it does not otherwise change what GetSharedModule does.
+static bool g_locate_executable_object_file_called = false;
+
+static std::optional<ModuleSpec> LocateExecutableObjectFile(const ModuleSpec &) {
+  g_locate_executable_object_file_called = true;
+  return {};
+}
+
+static SymbolLocator *CreateSymbolLocator() { return nullptr; }
+
+class SymbolLocatorGate : public testing::Test {
+public:
+  void SetUp() override {
+    g_locate_executable_object_file_called = false;
+    ASSERT_TRUE(PluginManager::RegisterPlugin(
+        "test", "test symbol locator", CreateSymbolLocator,
+        LocateExecutableObjectFile));
+  }
+
+  void TearDown() override {
+    PluginManager::UnregisterPlugin(CreateSymbolLocator);
+  }
+
+  // A spec that names no file on disk, so GetSharedModule has to fall through
+  // to the symbol locators to have any chance of finding a binary.
+  static ModuleSpec MissingModuleSpec() {
+    ModuleSpec spec;
+    spec.GetFileSpec() = FileSpec("/nonexistent/libtest.so");
+    spec.GetArchitecture() = ArchSpec("x86_64-pc-linux");
+    spec.GetUUID() = UUID("0123456789ABCDEF", 16);
+    return spec;
+  }
+};
+
+TEST_F(SymbolLocatorGate, GetSharedModuleInvokesSymbolLocatorsByDefault) {
+  SubsystemRAII<FileSystem, ObjectFileELF> subsystems;
+
+  ModuleSP module_sp;
+  ModuleList::GetSharedModule(MissingModuleSpec(), module_sp, nullptr, nullptr);
+
+  EXPECT_TRUE(g_locate_executable_object_file_called);
+}
+
+TEST_F(SymbolLocatorGate, GetSharedModuleCanSkipSymbolLocators) {
+  SubsystemRAII<FileSystem, ObjectFileELF> subsystems;
+
+  ModuleSP module_sp;
+  Status error = ModuleList::GetSharedModule(
+      MissingModuleSpec(), module_sp, nullptr, nullptr,
+      /*invoke_locate_callback=*/true, /*invoke_symbol_locators=*/false);
+
+  EXPECT_FALSE(g_locate_executable_object_file_called);
+  // The caller still learns that nothing was found.
+  EXPECT_FALSE(module_sp);
+  EXPECT_TRUE(error.Fail());
+}