Reapply PR/87550 (again) (#95571)

New fixes:
- properly init the `std::optional<std::vector>` to an empty vector as
opposed to `{}` (which was effectively `std::nullopt`).

---------

Co-authored-by: Vy Nguyen <[email protected]>

Author: oontvoo

lldb/include/lldb/API/SBDebugger.h

@@ -57,6 +57,8 @@ class LLDB_API SBDebugger {
 
   static const char *GetBroadcasterClass();
 
+  static bool SupportsLanguage(lldb::LanguageType language);
+
   lldb::SBBroadcaster GetBroadcaster();
 
   /// Get progress data from a SBEvent whose type is eBroadcastBitProgress.

lldb/include/lldb/Symbol/TypeSystem.h

@@ -209,6 +209,7 @@ class TypeSystem : public PluginInterface,
   // TypeSystems can support more than one language
   virtual bool SupportsLanguage(lldb::LanguageType language) = 0;
 
+  static bool SupportsLanguageStatic(lldb::LanguageType language);
   // Type Completion
 
   virtual bool GetCompleteType(lldb::opaque_compiler_type_t type) = 0;

lldb/source/API/SBDebugger.cpp

@@ -1742,3 +1742,7 @@ bool SBDebugger::InterruptRequested()   {
     return m_opaque_sp->InterruptRequested();
   return false;
 }
+
+bool SBDebugger::SupportsLanguage(lldb::LanguageType language) {
+  return TypeSystem::SupportsLanguageStatic(language);
+}

lldb/source/Symbol/TypeSystem.cpp

@@ -335,3 +335,14 @@ TypeSystemMap::GetTypeSystemForLanguage(lldb::LanguageType language,
   }
   return GetTypeSystemForLanguage(language);
 }
+
+bool TypeSystem::SupportsLanguageStatic(lldb::LanguageType language) {
+  if (language == eLanguageTypeUnknown || language >= eNumLanguageTypes)
+    return false;
+
+  LanguageSet languages =
+      PluginManager::GetAllTypeSystemSupportedLanguagesForTypes();
+  if (languages.Empty())
+    return false;
+  return languages[language];
+}

lldb/tools/lldb-dap/DAP.cpp

@@ -32,14 +32,7 @@ namespace lldb_dap {
 DAP g_dap;
 
 DAP::DAP()
-    : broadcaster("lldb-dap"),
-      exception_breakpoints(
-          {{"cpp_catch", "C++ Catch", lldb::eLanguageTypeC_plus_plus},
-           {"cpp_throw", "C++ Throw", lldb::eLanguageTypeC_plus_plus},
-           {"objc_catch", "Objective-C Catch", lldb::eLanguageTypeObjC},
-           {"objc_throw", "Objective-C Throw", lldb::eLanguageTypeObjC},
-           {"swift_catch", "Swift Catch", lldb::eLanguageTypeSwift},
-           {"swift_throw", "Swift Throw", lldb::eLanguageTypeSwift}}),
+    : broadcaster("lldb-dap"), exception_breakpoints(),
       focus_tid(LLDB_INVALID_THREAD_ID), stop_at_entry(false), is_attach(false),
       enable_auto_variable_summaries(false),
       enable_synthetic_child_debugging(false),
@@ -65,16 +58,62 @@ DAP::DAP()
 
 DAP::~DAP() = default;
 
+void DAP::PopulateExceptionBreakpoints() {
+  llvm::call_once(init_exception_breakpoints_flag, [this]() {
+    exception_breakpoints = std::vector<ExceptionBreakpoint> {};
+    
+    if (lldb::SBDebugger::SupportsLanguage(lldb::eLanguageTypeC_plus_plus)) {
+      exception_breakpoints->emplace_back("cpp_catch", "C++ Catch",
+                                          lldb::eLanguageTypeC_plus_plus);
+      exception_breakpoints->emplace_back("cpp_throw", "C++ Throw",
+                                          lldb::eLanguageTypeC_plus_plus);
+    }
+    if (lldb::SBDebugger::SupportsLanguage(lldb::eLanguageTypeObjC)) {
+      exception_breakpoints->emplace_back("objc_catch", "Objective-C Catch",
+                                          lldb::eLanguageTypeObjC);
+      exception_breakpoints->emplace_back("objc_throw", "Objective-C Throw",
+                                          lldb::eLanguageTypeObjC);
+    }
+    if (lldb::SBDebugger::SupportsLanguage(lldb::eLanguageTypeSwift)) {
+      exception_breakpoints->emplace_back("swift_catch", "Swift Catch",
+                                          lldb::eLanguageTypeSwift);
+      exception_breakpoints->emplace_back("swift_throw", "Swift Throw",
+                                          lldb::eLanguageTypeSwift);
+    }
+    assert(!exception_breakpoints->empty() && "should not be empty");
+  });
+}
+
 ExceptionBreakpoint *DAP::GetExceptionBreakpoint(const std::string &filter) {
-  for (auto &bp : exception_breakpoints) {
+  // PopulateExceptionBreakpoints() is called after g_dap.debugger is created
+  // in a request-initialize.
+  //
+  // But this GetExceptionBreakpoint() method may be called before attaching, in
+  // which case, we may not have populated the filter yet.
+  //
+  // We also cannot call PopulateExceptionBreakpoints() in DAP::DAP() because
+  // we need SBDebugger::Initialize() to have been called before this.
+  //
+  // So just calling PopulateExceptionBreakoints(),which does lazy-populating
+  // seems easiest. Two other options include:
+  //  + call g_dap.PopulateExceptionBreakpoints() in lldb-dap.cpp::main()
+  //    right after the call to SBDebugger::Initialize()
+  //  + Just call PopulateExceptionBreakpoints() to get a fresh list  everytime
+  //    we query (a bit overkill since it's not likely to change?)
+  PopulateExceptionBreakpoints();
+
+  for (auto &bp : *exception_breakpoints) {
     if (bp.filter == filter)
       return &bp;
   }
   return nullptr;
 }
 
 ExceptionBreakpoint *DAP::GetExceptionBreakpoint(const lldb::break_id_t bp_id) {
-  for (auto &bp : exception_breakpoints) {
+  // See comment in the other GetExceptionBreakpoint().
+  PopulateExceptionBreakpoints();
+
+  for (auto &bp : *exception_breakpoints) {
     if (bp.bp.GetID() == bp_id)
       return &bp;
   }

lldb/tools/lldb-dap/DAP.h

@@ -156,7 +156,8 @@ struct DAP {
   std::unique_ptr<std::ofstream> log;
   llvm::StringMap<SourceBreakpointMap> source_breakpoints;
   FunctionBreakpointMap function_breakpoints;
-  std::vector<ExceptionBreakpoint> exception_breakpoints;
+  std::optional<std::vector<ExceptionBreakpoint>> exception_breakpoints;
+  llvm::once_flag init_exception_breakpoints_flag;
   std::vector<std::string> init_commands;
   std::vector<std::string> pre_run_commands;
   std::vector<std::string> post_run_commands;
@@ -228,6 +229,8 @@ struct DAP {
 
   llvm::json::Value CreateTopLevelScopes();
 
+  void PopulateExceptionBreakpoints();
+
   /// \return
   ///   Attempt to determine if an expression is a variable expression or
   ///   lldb command using a hueristic based on the first term of the

lldb/tools/lldb-dap/lldb-dap.cpp

@@ -16,6 +16,7 @@
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
+#include <optional>
 #include <sys/stat.h>
 #include <sys/types.h>
 #if defined(_WIN32)
@@ -1586,6 +1587,7 @@ void request_initialize(const llvm::json::Object &request) {
   bool source_init_file = GetBoolean(arguments, "sourceInitFile", true);
 
   g_dap.debugger = lldb::SBDebugger::Create(source_init_file, log_cb, nullptr);
+  g_dap.PopulateExceptionBreakpoints();
   auto cmd = g_dap.debugger.GetCommandInterpreter().AddMultiwordCommand(
       "lldb-dap", "Commands for managing lldb-dap.");
   if (GetBoolean(arguments, "supportsStartDebuggingRequest", false)) {
@@ -1621,7 +1623,7 @@ void request_initialize(const llvm::json::Object &request) {
   body.try_emplace("supportsEvaluateForHovers", true);
   // Available filters or options for the setExceptionBreakpoints request.
   llvm::json::Array filters;
-  for (const auto &exc_bp : g_dap.exception_breakpoints) {
+  for (const auto &exc_bp : *g_dap.exception_breakpoints) {
     filters.emplace_back(CreateExceptionBreakpointFilter(exc_bp));
   }
   body.try_emplace("exceptionBreakpointFilters", std::move(filters));
@@ -2476,7 +2478,7 @@ void request_setExceptionBreakpoints(const llvm::json::Object &request) {
   // Keep a list of any exception breakpoint filter names that weren't set
   // so we can clear any exception breakpoints if needed.
   std::set<std::string> unset_filters;
-  for (const auto &bp : g_dap.exception_breakpoints)
+  for (const auto &bp : *g_dap.exception_breakpoints)
     unset_filters.insert(bp.filter);
 
   for (const auto &value : *filters) {