[lldb] Print lldbassert to debugger diagnostics

When hitting an lldbassert in a non-assert build, we emit a blurb
including the assertion, the triggering file and line and a pretty
backtrace leading up to the issue. Currently, this is all printed to
stderr. That's fine on the command line, but when used as library, for
example from Xcode, this information doesn't make it to the user. This
patch uses the diagnostic infrastructure to report LLDB asserts as
diagnostic events.

The patch is slightly more complicated than I would've liked because of
layering. lldbassert is part of Utility while the debugger diagnostics
are implemented in Core.

Differential revision: https://reviews.llvm.org/D152866

Author: JDevlieghere

lldb/include/lldb/Core/Debugger.h

@@ -128,6 +128,9 @@ class Debugger : public std::enable_shared_from_this<Debugger>,
                                         const ExecutionContext *exe_ctx,
                                         const Address *addr, Stream &s);
 
+  static void AssertCallback(llvm::StringRef message, llvm::StringRef backtrace,
+                             llvm::StringRef prompt);
+
   void Clear();
 
   bool GetAsyncExecution();

lldb/include/lldb/Utility/LLDBAssert.h

@@ -9,6 +9,8 @@
 #ifndef LLDB_UTILITY_LLDBASSERT_H
 #define LLDB_UTILITY_LLDBASSERT_H
 
+#include "llvm/ADT/StringRef.h"
+
 #ifndef NDEBUG
 #define lldbassert(x) assert(x)
 #else
@@ -29,6 +31,12 @@
 namespace lldb_private {
 void lldb_assert(bool expression, const char *expr_text, const char *func,
                  const char *file, unsigned int line);
+
+typedef void (*LLDBAssertCallback)(llvm::StringRef message,
+                                   llvm::StringRef backtrace,
+                                   llvm::StringRef prompt);
+
+void SetLLDBAssertCallback(LLDBAssertCallback callback);
 } // namespace lldb_private
 
 #endif // LLDB_UTILITY_LLDBASSERT_H

lldb/source/API/SystemInitializerFull.cpp

@@ -78,6 +78,9 @@ llvm::Error SystemInitializerFull::Initialize() {
   // Settings must be initialized AFTER PluginManager::Initialize is called.
   Debugger::SettingsInitialize();
 
+  // Use the Debugger's LLDBAssert callback.
+  SetLLDBAssertCallback(Debugger::AssertCallback);
+
   return llvm::Error::success();
 }
 

lldb/source/Core/Debugger.cpp

@@ -1352,6 +1352,13 @@ bool Debugger::FormatDisassemblerAddress(const FormatEntity::Entry *format,
                               function_changed, initial_function);
 }
 
+void Debugger::AssertCallback(llvm::StringRef message,
+                              llvm::StringRef backtrace,
+                              llvm::StringRef prompt) {
+  Debugger::ReportError(
+      llvm::formatv("{0}\n{1}{2}", message, backtrace, prompt).str());
+}
+
 void Debugger::SetLoggingCallback(lldb::LogOutputCallback log_callback,
                                   void *baton) {
   // For simplicity's sake, I am not going to deal with how to close down any

lldb/source/Utility/LLDBAssert.cpp

@@ -8,20 +8,29 @@
 
 #include "lldb/Utility/LLDBAssert.h"
 #include "llvm/Config/llvm-config.h"
-#include "llvm/Support/Format.h"
+#include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/raw_ostream.h"
 
 #if LLVM_SUPPORT_XCODE_SIGNPOSTS
 #include <os/log.h>
 #endif
 
-using namespace llvm;
-using namespace lldb_private;
+namespace lldb_private {
 
-void lldb_private::lldb_assert(bool expression, const char *expr_text,
-                               const char *func, const char *file,
-                               unsigned int line) {
+static void DefaultAssertCallback(llvm::StringRef message,
+                                  llvm::StringRef backtrace,
+                                  llvm::StringRef prompt) {
+  llvm::errs() << message << '\n';
+  llvm::errs() << backtrace; // Backtrace includes a newline.
+  llvm::errs() << prompt << '\n';
+}
+
+static std::atomic<LLDBAssertCallback> g_lldb_assert_callback =
+    &DefaultAssertCallback;
+
+void lldb_assert(bool expression, const char *expr_text, const char *func,
+                 const char *file, unsigned int line) {
   if (LLVM_LIKELY(expression))
     return;
 
@@ -35,10 +44,21 @@ void lldb_private::lldb_assert(bool expression, const char *expr_text,
 
   // Print a warning and encourage the user to file a bug report, similar to
   // LLVM’s crash handler, and then return execution.
-  errs() << format("Assertion failed: (%s), function %s, file %s, line %u\n",
-                   expr_text, func, file, line);
-  errs() << "backtrace leading to the failure:\n";
-  llvm::sys::PrintStackTrace(errs());
-  errs() << "please file a bug report against lldb reporting this failure "
-            "log, and as many details as possible\n";
+  std::string buffer;
+  llvm::raw_string_ostream backtrace(buffer);
+  llvm::sys::PrintStackTrace(backtrace);
+
+  (*g_lldb_assert_callback.load())(
+      llvm::formatv("Assertion failed: ({0}), function {1}, file {2}, line {3}",
+                    expr_text, func, file, line)
+          .str(),
+      backtrace.str(),
+      "Please file a bug report against lldb reporting this failure log, and "
+      "as many details as possible");
 }
+
+void SetLLDBAssertCallback(LLDBAssertCallback callback) {
+  g_lldb_assert_callback.exchange(callback);
+}
+
+} // namespace lldb_private