[Lldb-commits] [lldb] [lldb] Do not create/parse symtab during `DebuggerStats::ReportStatistics()` (PR #136236)

[via lldb-commits]

https://github.com/royitaqi created https://github.com/llvm/llvm-project/pull/136236

# The change

Currently, `DebuggerStats::ReportStatistics()` calls `Module::GetSymtab(/* can_create */ false)`, but then the latter calls `SymbolFile::GetSymtab()`. This will load symbols if haven't yet.

The problem is that `DebuggerStats::ReportStatistics` should be read-only. This is especially important because it reports stats for symtab parsing/indexing time, which could be affected by the reporting itself if it's not read-only.

This patch fixes this problem by adding an optional parameter `SymbolFile::GetSymtab(can_create = true)` and receive the `false` value passed down from `Module::GetSymtab()` when the call was initiated from `DebuggerStats::ReportStatistics()`.

# Tests

**Manually tested** with a helloworld program, that:
1. Without this patch, a breakpoint in `ObjectFileMachO::ParseSymtab()` is hit when we do `lldb a.out` then `statistics dump`.
2. With this patch, said breakpoint is not hit.

**Unit test**: Still looking for a good unit test file to add a new test. Will update here.

>From 85cb8cca4fe41cf4080b3dbf7ce4f98c4b15a3c7 Mon Sep 17 00:00:00 2001
From: Roy Shi <royshi at meta.com>
Date: Thu, 17 Apr 2025 15:03:00 -0700
Subject: [PATCH] [lldb] Do not parse symtab during statistics dump

Summary:

Test Plan:

Reviewers:

Subscribers:

Tasks:

Tags:

Differential Revision: https://phabricator.intern.facebook.com/D73218490
---
 lldb/include/lldb/Symbol/ObjectFile.h         | 2 +-
 lldb/include/lldb/Symbol/SymbolFile.h         | 4 ++--
 lldb/include/lldb/Symbol/SymbolFileOnDemand.h | 2 +-
 lldb/source/Core/Module.cpp                   | 2 +-
 lldb/source/Symbol/ObjectFile.cpp             | 4 ++--
 lldb/source/Symbol/SymbolFile.cpp             | 4 ++--
 6 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/lldb/include/lldb/Symbol/ObjectFile.h b/lldb/include/lldb/Symbol/ObjectFile.h
index cfcca04a76de8..7fca6383fa9f3 100644
--- a/lldb/include/lldb/Symbol/ObjectFile.h
+++ b/lldb/include/lldb/Symbol/ObjectFile.h
@@ -319,7 +319,7 @@ class ObjectFile : public std::enable_shared_from_this<ObjectFile>,
   ///
   /// \return
   ///     The symbol table for this object file.
-  Symtab *GetSymtab();
+  Symtab *GetSymtab(bool can_create = true);
 
   /// Parse the symbol table into the provides symbol table object.
   ///
diff --git a/lldb/include/lldb/Symbol/SymbolFile.h b/lldb/include/lldb/Symbol/SymbolFile.h
index f35d3ee9f22ae..df2f263b18e17 100644
--- a/lldb/include/lldb/Symbol/SymbolFile.h
+++ b/lldb/include/lldb/Symbol/SymbolFile.h
@@ -144,7 +144,7 @@ class SymbolFile : public PluginInterface {
   virtual uint32_t GetNumCompileUnits() = 0;
   virtual lldb::CompUnitSP GetCompileUnitAtIndex(uint32_t idx) = 0;
 
-  virtual Symtab *GetSymtab() = 0;
+  virtual Symtab *GetSymtab(bool can_create = true) = 0;
 
   virtual lldb::LanguageType ParseLanguage(CompileUnit &comp_unit) = 0;
   /// Return the Xcode SDK comp_unit was compiled against.
@@ -533,7 +533,7 @@ class SymbolFileCommon : public SymbolFile {
     return m_abilities;
   }
 
-  Symtab *GetSymtab() override;
+  Symtab *GetSymtab(bool can_create = true) override;
 
   ObjectFile *GetObjectFile() override { return m_objfile_sp.get(); }
   const ObjectFile *GetObjectFile() const override {
diff --git a/lldb/include/lldb/Symbol/SymbolFileOnDemand.h b/lldb/include/lldb/Symbol/SymbolFileOnDemand.h
index 7a366bfabec86..ce9fc8626ac34 100644
--- a/lldb/include/lldb/Symbol/SymbolFileOnDemand.h
+++ b/lldb/include/lldb/Symbol/SymbolFileOnDemand.h
@@ -186,7 +186,7 @@ class SymbolFileOnDemand : public lldb_private::SymbolFile {
 
   uint32_t GetAbilities() override;
 
-  Symtab *GetSymtab() override { return m_sym_file_impl->GetSymtab(); }
+  Symtab *GetSymtab(bool can_create = true) override { return m_sym_file_impl->GetSymtab(can_create); }
 
   ObjectFile *GetObjectFile() override {
     return m_sym_file_impl->GetObjectFile();
diff --git a/lldb/source/Core/Module.cpp b/lldb/source/Core/Module.cpp
index ad7046e596278..625c14e4a2153 100644
--- a/lldb/source/Core/Module.cpp
+++ b/lldb/source/Core/Module.cpp
@@ -997,7 +997,7 @@ SymbolFile *Module::GetSymbolFile(bool can_create, Stream *feedback_strm) {
 
 Symtab *Module::GetSymtab(bool can_create) {
   if (SymbolFile *symbols = GetSymbolFile(can_create))
-    return symbols->GetSymtab();
+    return symbols->GetSymtab(can_create);
   return nullptr;
 }
 
diff --git a/lldb/source/Symbol/ObjectFile.cpp b/lldb/source/Symbol/ObjectFile.cpp
index 2f2c59d6af620..292c00b9ac166 100644
--- a/lldb/source/Symbol/ObjectFile.cpp
+++ b/lldb/source/Symbol/ObjectFile.cpp
@@ -735,9 +735,9 @@ void llvm::format_provider<ObjectFile::Strata>::format(
 }
 
 
-Symtab *ObjectFile::GetSymtab() {
+Symtab *ObjectFile::GetSymtab(bool can_create) {
   ModuleSP module_sp(GetModule());
-  if (module_sp) {
+  if (module_sp && can_create) {
     // We can't take the module lock in ObjectFile::GetSymtab() or we can
     // deadlock in DWARF indexing when any file asks for the symbol table from
     // an object file. This currently happens in the preloading of symbols in
diff --git a/lldb/source/Symbol/SymbolFile.cpp b/lldb/source/Symbol/SymbolFile.cpp
index 94e32b55572dd..870d778dca740 100644
--- a/lldb/source/Symbol/SymbolFile.cpp
+++ b/lldb/source/Symbol/SymbolFile.cpp
@@ -152,10 +152,10 @@ void SymbolFile::AssertModuleLock() {
 
 SymbolFile::RegisterInfoResolver::~RegisterInfoResolver() = default;
 
-Symtab *SymbolFileCommon::GetSymtab() {
+Symtab *SymbolFileCommon::GetSymtab(bool can_create) {
   std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());
   // Fetch the symtab from the main object file.
-  auto *symtab = GetMainObjectFile()->GetSymtab();
+  auto *symtab = GetMainObjectFile()->GetSymtab(can_create);
   if (m_symtab != symtab) {
     m_symtab = symtab;