[Lldb-commits] [clang] [lldb] [UBSan][BoundsSafety] Implement support for more expressive "trap reasons" (PR #154618)

[via lldb-commits]

================
@@ -1534,6 +1536,103 @@ inline DiagnosticBuilder DiagnosticsEngine::Report(unsigned DiagID) {
   return Report(SourceLocation(), DiagID);
 }
 
+//===----------------------------------------------------------------------===//
+// RuntimeTrapDiagnosticBuilder and helper classes
+//===----------------------------------------------------------------------===//
+
+/// Helper class for \class RuntimeTrapDiagnosticBuilder. This class stores the
+/// "trap reason" built by \class RuntimeTrapDiagnosticBuilder. This consists of
+/// a trap message and trap category.
+///
+/// It is intended that this object be allocated on the stack.
+class TrapReason {
+public:
+  TrapReason() {}
+  /// \return The trap message. Note the lifetime of the underlying storage for
+  /// the returned StringRef lives in this class which means the returned
+  /// StringRef should not be used after this class is destroyed.
+  StringRef getMessage() const { return Message; }
+
+  /// \return the trap category (e.g. "Undefined Behavior Sanitizer")
+  StringRef getCategory() const { return Category; }
+
+  bool isEmpty() const { return Message.size() == 0 && Category.size() == 0; }
+
+  /// \return a pointer to this object if it contains a non-empty trap reason,
+  /// otherwise return `nullptr`. This is a convenient helper for passing
+  /// TrapReason objects to function calls that have a `TrapReason*` parameter.
+  TrapReason *getPtr() {
+    if (isEmpty())
+      return nullptr;
+    return this;
+  }
+
+private:
+  llvm::SmallString<64> Message;
+  // The Category doesn't need its own storage because the StringRef points
+  // to a global constant string.
+  StringRef Category;
+
+  // Only this class can set the private fields.
+  friend class RuntimeTrapDiagnosticBuilder;
+};
+
+/// Class to make it convenient to initialize TrapReason objects which can be
+/// used to attach the "trap reason" to trap instructions.
+///
+/// Although this class inherits from \class DiagnosticBuilder it has slightly
+/// different semantics.
+///
+/// * This class should only be used with trap diagnostics (declared in
+/// `DiagnosticTrapKinds.td`).
+/// * The `RuntimeTrapDiagnosticBuilder` does not emit diagnostics to the normal
+///   diagnostics consumers on destruction like normal Diagnostic builders.
+///   Instead on destruction it assigns to the TrapReason object passed in to
+///   the constructor.
+///
+/// Given that this class inherits from `DiagnosticBuilder` it inherits all of
+/// its abilities to format diagnostic messages and consume various types in
+/// class (e.g. Type, Exprs, etc.). This makes it particularly suited to
+/// printing types and expressions from the AST while codegen-ing runtime
+/// checks.
+///
+///
+/// Example use via the `CodeGenModule::RuntimeDiag` helper.
+///
+/// \code
+/// {
+///   TrapReason TR;
+///   CGM.RuntimeDiag(diag::trap_diagnostic, TR) << 0 << SomeExpr << SomeType;
+///   consume(TR.getPtr());
+/// }
+/// \endcode
+///
+///
+class RuntimeTrapDiagnosticBuilder : public DiagnosticBuilder {
+public:
+  RuntimeTrapDiagnosticBuilder(DiagnosticsEngine *DiagObj, unsigned DiagID,
+                               TrapReason &TR);
+  ~RuntimeTrapDiagnosticBuilder();
+
+  // Prevent accidentally copying or assigning
+  RuntimeTrapDiagnosticBuilder &
+  operator=(const RuntimeTrapDiagnosticBuilder &) = delete;
+  RuntimeTrapDiagnosticBuilder &
+  operator=(const RuntimeTrapDiagnosticBuilder &&) = delete;
+  RuntimeTrapDiagnosticBuilder(const RuntimeTrapDiagnosticBuilder &) = delete;
+  RuntimeTrapDiagnosticBuilder(const RuntimeTrapDiagnosticBuilder &&) = delete;
+
+  /// \return Format the trap message into `Storage`.
+  void getMessage(SmallVectorImpl<char> &Storage);
+
+  /// \return Return the trap category. These are the `CategoryName` property
+  /// of `trap` diagnostics declared in `DiagnosticTrapKinds.td`.
+  StringRef getCategory();
----------------
Sirraide wrote:

Since this is intended to be used w/ `TrapReason`, do these even need to be public?

https://github.com/llvm/llvm-project/pull/154618