[lldb] Add frame recognizer for __builtin_verbose_trap (#80368)

This patch adds a frame recognizer for Clang's
`__builtin_verbose_trap`, which behaves like a
`__builtin_trap`, but emits a failure-reason string into debug-info in
order for debuggers to display
it to a user.

The frame recognizer triggers when we encounter
a frame with a function name that begins with
`__clang_trap_msg`, which is the magic prefix
Clang emits into debug-info for verbose traps.
Once such frame is encountered we display the
frame function name as the `Stop Reason` and display that frame to the
user.

Example output:
```
(lldb) run
warning: a.out was compiled with optimization - stepping may behave oddly; variables may not be available.
Process 35942 launched: 'a.out' (arm64)
Process 35942 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = Misc.: Function is not implemented
    frame #1: 0x0000000100003fa4 a.out`main [inlined] Dummy::func(this=<unavailable>) at verbose_trap.cpp:3:5 [opt]
   1    struct Dummy {
   2      void func() {
-> 3        __builtin_verbose_trap("Misc.", "Function is not implemented");
   4      }
   5    };
   6
   7    int main() {
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = Misc.: Function is not implemented
    frame #0: 0x0000000100003fa4 a.out`main [inlined] __clang_trap_msg$Misc.$Function is not implemented$ at verbose_trap.cpp:0 [opt]
  * frame #1: 0x0000000100003fa4 a.out`main [inlined] Dummy::func(this=<unavailable>) at verbose_trap.cpp:3:5 [opt]
    frame #2: 0x0000000100003fa4 a.out`main at verbose_trap.cpp:8:13 [opt]
    frame #3: 0x0000000189d518b4 dyld`start + 1988
```

lldb/include/lldb/Target/VerboseTrapFrameRecognizer.h

@@ -0,0 +1,39 @@
+#ifndef LLDB_TARGET_VERBOSETRAPFRAMERECOGNIZER_H
+#define LLDB_TARGET_VERBOSETRAPFRAMERECOGNIZER_H
+
+#include "lldb/Target/StackFrameRecognizer.h"
+
+namespace lldb_private {
+
+void RegisterVerboseTrapFrameRecognizer(Process &process);
+
+/// Holds the stack frame that caused the Verbose trap and the inlined stop
+/// reason message.
+class VerboseTrapRecognizedStackFrame : public RecognizedStackFrame {
+public:
+  VerboseTrapRecognizedStackFrame(lldb::StackFrameSP most_relevant_frame_sp,
+                                  std::string stop_desc);
+
+  lldb::StackFrameSP GetMostRelevantFrame() override;
+
+private:
+  lldb::StackFrameSP m_most_relevant_frame;
+};
+
+/// When a thread stops, it checks the current frame contains a
+/// Verbose Trap diagnostic. If so, it returns a \a
+/// VerboseTrapRecognizedStackFrame holding the diagnostic a stop reason
+/// description with and the parent frame as the most relavant frame.
+class VerboseTrapFrameRecognizer : public StackFrameRecognizer {
+public:
+  std::string GetName() override {
+    return "Verbose Trap StackFrame Recognizer";
+  }
+
+  lldb::RecognizedStackFrameSP
+  RecognizeFrame(lldb::StackFrameSP frame) override;
+};
+
+} // namespace lldb_private
+
+#endif // LLDB_TARGET_VERBOSETRAPFRAMERECOGNIZER_H

lldb/source/Target/CMakeLists.txt

@@ -78,6 +78,7 @@ add_lldb_library(lldbTarget
   UnixSignals.cpp
   UnwindAssembly.cpp
   UnwindLLDB.cpp
+  VerboseTrapFrameRecognizer.cpp
 
   LINK_LIBS
     lldbBreakpoint

lldb/source/Target/Process.cpp

@@ -63,6 +63,7 @@
 #include "lldb/Target/ThreadPlanCallFunction.h"
 #include "lldb/Target/ThreadPlanStack.h"
 #include "lldb/Target/UnixSignals.h"
+#include "lldb/Target/VerboseTrapFrameRecognizer.h"
 #include "lldb/Utility/AddressableBits.h"
 #include "lldb/Utility/Event.h"
 #include "lldb/Utility/LLDBLog.h"
@@ -522,7 +523,11 @@ Process::Process(lldb::TargetSP target_sp, ListenerSP listener_sp,
   if (!value_sp->OptionWasSet() && platform_cache_line_size != 0)
     value_sp->SetValueAs(platform_cache_line_size);
 
+  // FIXME: Frame recognizer registration should not be done in Target.
+  // We should have a plugin do the registration instead, for example, a
+  // common C LanguageRuntime plugin.
   RegisterAssertFrameRecognizer(this);
+  RegisterVerboseTrapFrameRecognizer(*this);
 }
 
 Process::~Process() {

lldb/source/Target/VerboseTrapFrameRecognizer.cpp

@@ -0,0 +1,122 @@
+#include "lldb/Target/VerboseTrapFrameRecognizer.h"
+
+#include "lldb/Core/Module.h"
+#include "lldb/Symbol/Function.h"
+#include "lldb/Symbol/SymbolContext.h"
+#include "lldb/Target/Process.h"
+#include "lldb/Target/StackFrameRecognizer.h"
+#include "lldb/Target/Target.h"
+
+#include "lldb/Utility/LLDBLog.h"
+#include "lldb/Utility/Log.h"
+
+#include "clang/CodeGen/ModuleBuilder.h"
+
+using namespace llvm;
+using namespace lldb;
+using namespace lldb_private;
+
+VerboseTrapRecognizedStackFrame::VerboseTrapRecognizedStackFrame(
+    StackFrameSP most_relevant_frame_sp, std::string stop_desc)
+    : m_most_relevant_frame(most_relevant_frame_sp) {
+  m_stop_desc = std::move(stop_desc);
+}
+
+lldb::RecognizedStackFrameSP
+VerboseTrapFrameRecognizer::RecognizeFrame(lldb::StackFrameSP frame_sp) {
+  if (frame_sp->GetFrameIndex())
+    return {};
+
+  ThreadSP thread_sp = frame_sp->GetThread();
+  ProcessSP process_sp = thread_sp->GetProcess();
+
+  StackFrameSP most_relevant_frame_sp = thread_sp->GetStackFrameAtIndex(1);
+
+  if (!most_relevant_frame_sp) {
+    Log *log = GetLog(LLDBLog::Unwind);
+    LLDB_LOG(
+        log,
+        "Failed to find most relevant frame: Hit unwinding bound (1 frame)!");
+    return {};
+  }
+
+  SymbolContext sc = frame_sp->GetSymbolContext(eSymbolContextEverything);
+
+  if (!sc.block)
+    return {};
+
+  // The runtime error is set as the function name in the inlined function info
+  // of frame #0 by the compiler
+  const InlineFunctionInfo *inline_info = nullptr;
+  Block *inline_block = sc.block->GetContainingInlinedBlock();
+
+  if (!inline_block)
+    return {};
+
+  inline_info = sc.block->GetInlinedFunctionInfo();
+
+  if (!inline_info)
+    return {};
+
+  auto func_name = inline_info->GetName().GetStringRef();
+  if (func_name.empty())
+    return {};
+
+  static auto trap_regex =
+      llvm::Regex(llvm::formatv("^{0}\\$(.*)\\$(.*)$", ClangTrapPrefix).str());
+  SmallVector<llvm::StringRef, 3> matches;
+  std::string regex_err_msg;
+  if (!trap_regex.match(func_name, &matches, &regex_err_msg)) {
+    LLDB_LOGF(GetLog(LLDBLog::Unwind),
+              "Failed to parse match trap regex for '%s': %s", func_name.data(),
+              regex_err_msg.c_str());
+
+    return {};
+  }
+
+  // For `__clang_trap_msg$category$message$` we expect 3 matches:
+  // 1. entire string
+  // 2. category
+  // 3. message
+  if (matches.size() != 3) {
+    LLDB_LOGF(GetLog(LLDBLog::Unwind),
+              "Unexpected function name format. Expected '<trap prefix>$<trap "
+              "category>$<trap message>'$ but got: '%s'.",
+              func_name.data());
+
+    return {};
+  }
+
+  auto category = matches[1];
+  auto message = matches[2];
+
+  std::string stop_reason =
+      category.empty() ? "<empty category>" : category.str();
+  if (!message.empty()) {
+    stop_reason += ": ";
+    stop_reason += message.str();
+  }
+
+  return std::make_shared<VerboseTrapRecognizedStackFrame>(
+      most_relevant_frame_sp, std::move(stop_reason));
+}
+
+lldb::StackFrameSP VerboseTrapRecognizedStackFrame::GetMostRelevantFrame() {
+  return m_most_relevant_frame;
+}
+
+namespace lldb_private {
+
+void RegisterVerboseTrapFrameRecognizer(Process &process) {
+  RegularExpressionSP module_regex_sp = nullptr;
+  auto symbol_regex_sp = std::make_shared<RegularExpression>(
+      llvm::formatv("^{0}", ClangTrapPrefix).str());
+
+  StackFrameRecognizerSP srf_recognizer_sp =
+      std::make_shared<VerboseTrapFrameRecognizer>();
+
+  process.GetTarget().GetFrameRecognizerManager().AddRecognizer(
+      srf_recognizer_sp, module_regex_sp, symbol_regex_sp, false);
+}
+
+} // namespace lldb_private

lldb/test/Shell/Recognizer/Inputs/verbose_trap.cpp

@@ -0,0 +1,12 @@
+#if !defined(VERBOSE_TRAP_TEST_CATEGORY) || !defined(VERBOSE_TRAP_TEST_MESSAGE)
+#error Please define required macros
+#endif
+
+struct Dummy {
+  void func() { __builtin_verbose_trap(VERBOSE_TRAP_TEST_CATEGORY, VERBOSE_TRAP_TEST_MESSAGE); }
+};
+
+int main() {
+  Dummy{}.func();
+  return 0;
+}

lldb/test/Shell/Recognizer/verbose_trap.test

@@ -0,0 +1,22 @@
+# RUN: %clang_host -g -O0 %S/Inputs/verbose_trap.cpp -o %t.out -DVERBOSE_TRAP_TEST_CATEGORY=\"Foo\" -DVERBOSE_TRAP_TEST_MESSAGE=\"Bar\"
+# RUN: %lldb -b -s %s %t.out | FileCheck %s --check-prefixes=CHECK,CHECK-BOTH
+#
+# RUN: %clang_host -g -O0 %S/Inputs/verbose_trap.cpp -o %t.out -DVERBOSE_TRAP_TEST_CATEGORY=\"\" -DVERBOSE_TRAP_TEST_MESSAGE=\"Bar\"
+# RUN: %lldb -b -s %s %t.out | FileCheck %s --check-prefixes=CHECK,CHECK-MESSAGE_ONLY
+#
+# RUN: %clang_host -g -O0 %S/Inputs/verbose_trap.cpp -o %t.out -DVERBOSE_TRAP_TEST_CATEGORY=\"Foo\" -DVERBOSE_TRAP_TEST_MESSAGE=\"\"
+# RUN: %lldb -b -s %s %t.out | FileCheck %s --check-prefixes=CHECK,CHECK-CATEGORY_ONLY
+#
+# RUN: %clang_host -g -O0 %S/Inputs/verbose_trap.cpp -o %t.out -DVERBOSE_TRAP_TEST_CATEGORY=\"\" -DVERBOSE_TRAP_TEST_MESSAGE=\"\"
+# RUN: %lldb -b -s %s %t.out | FileCheck %s --check-prefixes=CHECK,CHECK-NONE
+
+run
+# CHECK-BOTH:          thread #{{.*}}stop reason = Foo: Bar
+# CHECK-MESSAGE_ONLY:  thread #{{.*}}stop reason = <empty category>: Bar
+# CHECK-CATEGORY_ONLY: thread #{{.*}}stop reason = Foo
+# CHECK-NONE:          thread #{{.*}}stop reason = <empty category>
+frame info
+# CHECK: frame #{{.*}}`Dummy::func(this={{.*}}) at verbose_trap.cpp
+frame recognizer info 0
+# CHECK: frame 0 is recognized by Verbose Trap StackFrame Recognizer
+q