[lldb/cpluspluslanguage] Add constructor substitutor

Summary:
This patch adds code which will substitute references to the full object
constructors/destructors with their base object versions.

Like all substitutions in this category, this operation is not really
sound, but doing this in a more precise way allows us to get rid of a
much larger hack -- matching function according to their demangled
names, which effectively does the same thing, but also much more.

This is a (very late) follow-up to D54074.

Background: clang has an optimization which can eliminate full object
structors completely, if they are found to be equivalent to their base
object versions. It does this because it assumes they can be regenerated
on demand in the compile unit that needs them (e.g., because they are
declared inline). However, this doesn't work for the debugging scenario,
where we don't have the structor bodies available -- we pretend all
constructors are defined out-of-line as far as clang is concerned. This
causes clang to emit references to the (nonexisting) full object
structors during expression evaluation.

Fun fact: This is not a problem on darwin, because the relevant
optimization is disabled to work around a linker bug.

Reviewers: teemperor, JDevlieghere

Subscribers: lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D70721

1 files changed, 82 insertions, 41 deletions

diff --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
index c22f4ae9e41..4385a60f586 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
@@ -284,46 +284,34 @@ public:
   }
 };
 
-/// Given a mangled function `Mangled`, replace all the primitive function type
-/// arguments of `Search` with type `Replace`.
-class TypeSubstitutor
-    : public llvm::itanium_demangle::AbstractManglingParser<TypeSubstitutor,
+template <typename Derived>
+class ManglingSubstitutor
+    : public llvm::itanium_demangle::AbstractManglingParser<Derived,
                                                             NodeAllocator> {
-  /// Input character until which we have constructed the respective output
-  /// already
-  const char *Written;
+  using Base =
+      llvm::itanium_demangle::AbstractManglingParser<Derived, NodeAllocator>;
 
-  llvm::StringRef Search;
-  llvm::StringRef Replace;
-  llvm::SmallString<128> Result;
+public:
+  ManglingSubstitutor() : Base(nullptr, nullptr) {}
 
-  /// Whether we have performed any substitutions.
-  bool Substituted;
+  template<typename... Ts>
+  ConstString substitute(llvm::StringRef Mangled, Ts &&... Vals) {
+    this->getDerived().reset(Mangled, std::forward<Ts>(Vals)...);
+    return substituteImpl(Mangled);
+  }
 
-  void reset(llvm::StringRef Mangled, llvm::StringRef Search,
-             llvm::StringRef Replace) {
-    AbstractManglingParser::reset(Mangled.begin(), Mangled.end());
+
+protected:
+  void reset(llvm::StringRef Mangled) {
+    Base::reset(Mangled.begin(), Mangled.end());
     Written = Mangled.begin();
-    this->Search = Search;
-    this->Replace = Replace;
     Result.clear();
     Substituted = false;
   }
 
-  void appendUnchangedInput() {
-    Result += llvm::StringRef(Written, First - Written);
-    Written = First;
-  }
-
-public:
-  TypeSubstitutor() : AbstractManglingParser(nullptr, nullptr) {}
-
-  ConstString substitute(llvm::StringRef Mangled, llvm::StringRef From,
-                         llvm::StringRef To) {
+  ConstString substituteImpl(llvm::StringRef Mangled) {
     Log *log = GetLogIfAllCategoriesSet(LIBLLDB_LOG_LANGUAGE);
-
-    reset(Mangled, From, To);
-    if (parse() == nullptr) {
+    if (this->parse() == nullptr) {
       LLDB_LOG(log, "Failed to substitute mangling in {0}", Mangled);
       return ConstString();
     }
@@ -336,20 +324,69 @@ public:
     return ConstString(Result);
   }
 
+  void trySubstitute(llvm::StringRef From, llvm::StringRef To) {
+    if (!llvm::StringRef(currentParserPos(), this->numLeft()).startswith(From))
+      return;
+
+    // We found a match. Append unmodified input up to this point.
+    appendUnchangedInput();
+
+    // And then perform the replacement.
+    Result += To;
+    Written += From.size();
+    Substituted = true;
+  }
+
+private:
+  /// Input character until which we have constructed the respective output
+  /// already.
+  const char *Written;
+
+  llvm::SmallString<128> Result;
+
+  /// Whether we have performed any substitutions.
+  bool Substituted;
+
+  const char *currentParserPos() const { return this->First; }
+
+  void appendUnchangedInput() {
+    Result +=
+        llvm::StringRef(Written, std::distance(Written, currentParserPos()));
+    Written = currentParserPos();
+  }
+
+};
+
+/// Given a mangled function `Mangled`, replace all the primitive function type
+/// arguments of `Search` with type `Replace`.
+class TypeSubstitutor : public ManglingSubstitutor<TypeSubstitutor> {
+  llvm::StringRef Search;
+  llvm::StringRef Replace;
+
+public:
+  void reset(llvm::StringRef Mangled, llvm::StringRef Search,
+             llvm::StringRef Replace) {
+    ManglingSubstitutor::reset(Mangled);
+    this->Search = Search;
+    this->Replace = Replace;
+  }
+
   llvm::itanium_demangle::Node *parseType() {
-    if (llvm::StringRef(First, numLeft()).startswith(Search)) {
-      // We found a match. Append unmodified input up to this point.
-      appendUnchangedInput();
-
-      // And then perform the replacement.
-      Result += Replace;
-      Written += Search.size();
-      Substituted = true;
-    }
-    return AbstractManglingParser::parseType();
+    trySubstitute(Search, Replace);
+    return ManglingSubstitutor::parseType();
   }
 };
-}
+
+class CtorDtorSubstitutor : public ManglingSubstitutor<CtorDtorSubstitutor> {
+public:
+  llvm::itanium_demangle::Node *
+  parseCtorDtorName(llvm::itanium_demangle::Node *&SoFar, NameState *State) {
+    trySubstitute("C1", "C2");
+    trySubstitute("D1", "D2");
+    return ManglingSubstitutor::parseCtorDtorName(SoFar, State);
+  }
+};
+} // namespace
 
 uint32_t CPlusPlusLanguage::FindAlternateFunctionManglings(
     const ConstString mangled_name, std::set<ConstString> &alternates) {
@@ -397,6 +434,10 @@ uint32_t CPlusPlusLanguage::FindAlternateFunctionManglings(
           TS.substitute(mangled_name.GetStringRef(), "y", "m"))
     alternates.insert(ulong_fixup);
 
+  if (ConstString ctor_fixup =
+          CtorDtorSubstitutor().substitute(mangled_name.GetStringRef()))
+    alternates.insert(ctor_fixup);
+
   return alternates.size() - start_size;
 }