[Lldb-commits] [lldb] [lldb/Target] Add SyntheticFrameProvider class (PR #166664)

[Jonas Devlieghere via lldb-commits]

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+
+//===------------------------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLDB_TARGET_SYNTHETICFRAMEPROVIDER_H
+#define LLDB_TARGET_SYNTHETICFRAMEPROVIDER_H
+
+#include "lldb/Core/PluginInterface.h"
+#include "lldb/Target/StackFrameList.h"
+#include "lldb/Target/ThreadSpec.h"
+#include "lldb/Utility/ScriptedMetadata.h"
+#include "lldb/Utility/Status.h"
+#include "lldb/lldb-forward.h"
+#include "llvm/Support/Error.h"
+
+#include <optional>
+#include <vector>
+
+namespace lldb_private {
+
+/// Descriptor for configuring a synthetic frame provider.
+///
+/// This struct contains the metadata needed to instantiate a frame provider
+/// and optional filters to control which threads it applies to.
+struct SyntheticFrameProviderDescriptor {
+  /// Metadata for instantiating the provider (e.g., script class name and args)
+  lldb::ScriptedMetadataSP scripted_metadata_sp;
+
+  /// Optional list of thread specifications to which this provider applies.
+  /// If empty, the provider applies to all threads. A thread matches if it
+  /// satisfies ANY of the specs in this vector (OR logic).
+  std::vector<ThreadSpec> thread_specs;
+
+  SyntheticFrameProviderDescriptor() = default;
+
+  SyntheticFrameProviderDescriptor(lldb::ScriptedMetadataSP metadata_sp)
+      : scripted_metadata_sp(metadata_sp) {}
+
+  SyntheticFrameProviderDescriptor(lldb::ScriptedMetadataSP metadata_sp,
+                                   const std::vector<ThreadSpec> &specs)
+      : scripted_metadata_sp(metadata_sp), thread_specs(specs) {}
+
+  /// Get the name of this descriptor (the scripted class name).
+  llvm::StringRef GetName() const {
+    return scripted_metadata_sp ? scripted_metadata_sp->GetClassName() : "";
+  }
+
+  /// Check if this descriptor applies to the given thread.
+  bool AppliesToThread(Thread &thread) const {
+    // If no thread specs specified, applies to all threads
+    if (thread_specs.empty())
+      return true;
+
+    // Check if the thread matches any of the specs (OR logic)
+    for (const auto &spec : thread_specs) {
+      if (spec.ThreadPassesBasicTests(thread))
+        return true;
+    }
+    return false;
+  }
+
+  /// Check if this descriptor has valid metadata.
+  bool IsValid() const { return scripted_metadata_sp != nullptr; }
+
+  void Dump(Stream *s) const;
+};
+
+/// Base class for all synthetic frame providers.
+///
+/// Synthetic frame providers allow modifying or replacing the stack frames
+/// shown for a thread. This is useful for:
+/// - Providing frames for custom calling conventions or languages
+/// - Reconstructing missing frames from crash dumps or core files
+/// - Adding diagnostic or synthetic frames for debugging
+/// - Visualizing state machines or async execution contexts
+class SyntheticFrameProvider : public PluginInterface {
+public:
+  /// Try to create a SyntheticFrameProvider instance for the given input
+  /// frames and descriptor.
+  ///
+  /// This method iterates through all registered SyntheticFrameProvider
+  /// plugins and returns the first one that can handle the given descriptor.
+  ///
+  /// \param[in] input_frames
+  ///     The input stack frame list that this provider will transform.
+  ///     This could be real unwound frames or output from another provider.
+  ///
+  /// \param[in] descriptor
+  ///     The descriptor containing metadata for the provider.
+  ///
+  /// \return
+  ///     A shared pointer to a SyntheticFrameProvider if one could be created,
+  ///     otherwise an \a llvm::Error.
+  static llvm::Expected<lldb::SyntheticFrameProviderSP>
+  CreateInstance(lldb::StackFrameListSP input_frames,
+                 const SyntheticFrameProviderDescriptor &descriptor);
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JDevlieghere wrote:

See my point above, I think this class should take a `thread_specs` instead, and you can do the bridging with the descriptor in the ScriptedFrameProvider

https://github.com/llvm/llvm-project/pull/166664