From 7d7603c98c8a843583aa6b113afe2ec0f33dc0a7 Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12@gmail.com>
Date: Wed, 12 Nov 2025 12:13:16 +0000
Subject: [PATCH] [lldb][Language] Pass SymbolNameFitsToLanguage parameter by
 const-ref

We've been seeing (rare) crashes from both `CPlusPlusLanguage::SymbolNameFitsToLanguage` and `ObjCLanguage::SymbolNameFitsToLanguage` when we try to read contents of the `ConstString`s of the `Mangled` parameter. I'm not entirely sure how that can happen (current theory is corrupted stack somehow which overwrites `ConstString::m_string` to an invalid pointer) but I'm not able to confirm that.

One thing these crashes had in common is that they operate on the
`Mangled` object we copied into `SymbolNameFitsToLanguage` by value.
While I can't see off the top why that would cause it to contain
unintiailized/corrupt `ConstString`s, the class is sufficiently large
enough to probably pass it by `const &` anyway. This is what this patch
does.

rdar://164519648
---
 lldb/include/lldb/Target/Language.h                          | 4 +++-
 lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp | 2 +-
 lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.h   | 2 +-
 lldb/source/Plugins/Language/ObjC/ObjCLanguage.cpp           | 2 +-
 lldb/source/Plugins/Language/ObjC/ObjCLanguage.h             | 2 +-
 5 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/lldb/include/lldb/Target/Language.h b/lldb/include/lldb/Target/Language.h
index 9958b6ea2f815..9292f790333a1 100644
--- a/lldb/include/lldb/Target/Language.h
+++ b/lldb/include/lldb/Target/Language.h
@@ -318,7 +318,9 @@ class Language : public PluginInterface {
   ///
   /// This function should only return true if there is a high confidence
   /// that the name actually belongs to this language.
-  virtual bool SymbolNameFitsToLanguage(Mangled name) const { return false; }
+  virtual bool SymbolNameFitsToLanguage(const Mangled &name) const {
+    return false;
+  }
 
   /// An individual data formatter may apply to several types and cross language
   /// boundaries. Each of those languages may want to customize the display of
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
index a2199cb65cd35..e935ea8fab813 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
@@ -103,7 +103,7 @@ CPlusPlusLanguage::GetFunctionNameInfo(ConstString name) const {
     return {func_name_type, ConstString(basename)};
 }
 
-bool CPlusPlusLanguage::SymbolNameFitsToLanguage(Mangled mangled) const {
+bool CPlusPlusLanguage::SymbolNameFitsToLanguage(const Mangled &mangled) const {
   auto mangling_scheme =
       Mangled::GetManglingScheme(mangled.GetMangledName().GetStringRef());
   return mangling_scheme == Mangled::eManglingSchemeItanium ||
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.h b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.h
index 9a528ca7b03f9..13d436a68c691 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.h
+++ b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.h
@@ -92,7 +92,7 @@ class CPlusPlusLanguage : public Language {
 
   static llvm::StringRef GetPluginNameStatic() { return "cplusplus"; }
 
-  bool SymbolNameFitsToLanguage(Mangled mangled) const override;
+  bool SymbolNameFitsToLanguage(const Mangled &mangled) const override;
 
   bool DemangledNameContainsPath(llvm::StringRef path,
                                  ConstString demangled) const override;
diff --git a/lldb/source/Plugins/Language/ObjC/ObjCLanguage.cpp b/lldb/source/Plugins/Language/ObjC/ObjCLanguage.cpp
index 3b8e21cbb9269..5e31faccb315c 100644
--- a/lldb/source/Plugins/Language/ObjC/ObjCLanguage.cpp
+++ b/lldb/source/Plugins/Language/ObjC/ObjCLanguage.cpp
@@ -235,7 +235,7 @@ ObjCLanguage::GetFunctionNameInfo(ConstString name) const {
   return {func_name_type, std::nullopt};
 }
 
-bool ObjCLanguage::SymbolNameFitsToLanguage(Mangled mangled) const {
+bool ObjCLanguage::SymbolNameFitsToLanguage(const Mangled &mangled) const {
   ConstString demangled_name = mangled.GetDemangledName();
   if (!demangled_name)
     return false;
diff --git a/lldb/source/Plugins/Language/ObjC/ObjCLanguage.h b/lldb/source/Plugins/Language/ObjC/ObjCLanguage.h
index a68ea41c723de..729230dc2dccb 100644
--- a/lldb/source/Plugins/Language/ObjC/ObjCLanguage.h
+++ b/lldb/source/Plugins/Language/ObjC/ObjCLanguage.h
@@ -145,7 +145,7 @@ class ObjCLanguage : public Language {
   std::pair<lldb::FunctionNameType, std::optional<ConstString>>
   GetFunctionNameInfo(ConstString name) const override;
 
-  bool SymbolNameFitsToLanguage(Mangled mangled) const override;
+  bool SymbolNameFitsToLanguage(const Mangled &mangled) const override;
 
   lldb::TypeCategoryImplSP GetFormatters() override;