add range tracking when demangling a name #82298

charles-zablit · 2025-06-17T15:27:10Z

This PR implements range tracking for the name and parameters of a demangled function.

Motivation

In this patch, @Michael137 implemented name highlighting for methods in the C++ plugin of LLDB. This results in better readability when reading backtraces of functions with long scopes.

I am working on implementing the same feature for the Swift plugin in LLDB. Please see an example below:
Before:

After:

Notice how the name and parameters of the functions are highlighted differently than the rest.
(Please note that the difference in text contents are temporary, and should disappear before for the final patch).

Implementation details

To implement this feature in the Swift plugin of LLDB, we need to provide LLDB with the ranges of the "components" of the demangled name. For instance the baseName of bar.foo() spans 4...7, while the parameters span 7...9.

This information allows LLDB to build the name that is displayed in the backtraces.

Original implementation

This patch introduces a new class called TrackingDemanglerPrinter which stores the information needed to track the ranges. It can later be extended to track more ranges. The methods it defines are called in the print method of NodePrinter.cpp.

The previous behavior is still available when calling DemangleSymbolAsString without a printer, as this will result in a no op when startName is called for instance.

Current implementation

2 methods were made virtual in NodePrinter, so that any consumer can override them and track the ranges they need. This is less lldb specific than the previous method.

Testing (removed, relevant only for the original implementation)

To implement the tests for the range tracking, I used the manglings.txt file. It now contains the ranges for the name and parameters where that's relevant. The format I chose to serialize the ranges is arbitrary and I'm happy to discuss any change, especially when considering we might want to add more tracked ranges.

I also developed a Python script to help review the test cases by coloring them. Please find it here for reference. It could be interesting to add it to the repo.

Follow ups

We will need to track more than just the name and the parameters to implement the changes in the LLDB plugin. We will also need the qualifiers, return type and probably a catch all "suffix".
It could be interesting to implement syntax highlighting in swift-demangle, as these changes make it fairly trivial to implement, and it would greatly help with readability.

Please note that it was originally opened here #81511 but I moved to a different target branch.

This PR depends on #82303

adrian-prantl · 2025-06-17T20:03:12Z

Are these cherry-picks from main? If not, can you rebase this PR to main and then create another PR that just cherry-picks this to the release branch?

(In case you are wondering: yes, this is exactly the inverse workflow that LLDB uses).

Michael137 · 2025-06-18T09:17:22Z

include/swift/Demangling/Demangle.h

+class DemanglerPrinter;
+
+class TrackingDemanglerPrinter;


Suggested change

class DemanglerPrinter;

class TrackingDemanglerPrinter;

Don't think these are needed

Removed in:

add new methods to the NodePrinter to enable range tracking possibilities when demangling a name #82336

Michael137 · 2025-06-18T09:18:16Z

include/swift/Demangling/Demangle.h

+
+  /// Demangle the given symbol.
+  ///
+  /// \param MangledName The mangled symbol string, which start a mangling


Suggested change

/// \param MangledName The mangled symbol string, which start a mangling

/// \param MangledName The mangled symbol string, which start with a mangling

?

Not sure where this came from, probably a bad copy paste. Removed in:

add new methods to the NodePrinter to enable range tracking possibilities when demangling a name #82336

Michael137 · 2025-06-18T09:18:51Z

include/swift/Demangling/Demangle.h

+  /// prefix: _T, _T0, $S, _$S.
+  /// \param printer The NodePrinter that will be used to demangle the symbol.
+  ///
+  /// \returns The demangled string.


This function doesn't return anything though.

Adjusted the doxygen of this method and a few others in:

add new methods to the NodePrinter to enable range tracking possibilities when demangling a name #82336

Michael137 · 2025-06-18T09:19:16Z

include/swift/Demangling/Demangle.h

+  demangleSymbolAsString(llvm::StringRef MangledName,
+                         const DemangleOptions &Options = DemangleOptions());
+
+  /// Demangle the given symbol.


Lets briefly describe what the intended usage of this overload is

Fixed in:

add new methods to the NodePrinter to enable range tracking possibilities when demangling a name #82336

Michael137

Could you separate out the changes that move the NodePrinter class into a separate NFC PR? And then only include the "range tracking" parts here?

Michael137 · 2025-06-18T10:23:20Z

Oh I see you did that in two separate commits. That should be fine then

Michael137 · 2025-06-18T10:25:48Z

include/swift/Demangling/Demangle.h

@@ -236,6 +237,18 @@ class Node {
 public:
  Kind getKind() const { return NodeKind; }

+  bool shouldTrackNameRange() const {


Where is this used?

It's used here: https://github.com/swiftlang/llvm-project/pull/10710/files#diff-5c0cd3ffc206ebb1e41b4984b7629c896aa79951708915cfafff560b1da51aa1

The code was moved there instead because it does not make sense to have it in the swift repo. It has been removed in:

add new methods to the NodePrinter to enable range tracking possibilities when demangling a name #82336

Michael137 · 2025-06-18T10:26:12Z

lib/Demangling/NodePrinter.cpp

@@ -3568,6 +3568,43 @@ NodePointer NodePrinter::printEntity(NodePointer Entity, unsigned depth,
  return PostfixContext;
 }

+void NodePrinter::printFunctionName(bool hasName,


Has this function just been moved? Or has it been adjusted?

It's a new function which was extracted from the printEntity function.

Michael137 · 2025-06-18T10:26:45Z

include/swift/Demangling/Demangle.h

+public:
+  NodePrinter(DemangleOptions options) : Options(options) {}
+
+  virtual ~NodePrinter() {}


Suggested change

virtual ~NodePrinter() {}

virtual ~NodePrinter() = default

Fixed in:

add new methods to the NodePrinter to enable range tracking possibilities when demangling a name #82336

charles-zablit · 2025-06-18T11:55:39Z

Moved the PR here:

add new methods to the NodePrinter to enable range tracking possibilities when demangling a name #82336

This allows to target main without pinging a lot of reviewers.

charles-zablit requested a review from a team as a code owner June 17, 2025 15:27

charles-zablit requested review from rintaro, adrian-prantl and Michael137 June 17, 2025 15:27

charles-zablit self-assigned this Jun 17, 2025

charles-zablit added the demangling Area → compiler: The `libswiftDemangling` library label Jun 17, 2025

move NodePrinter declarations to a header

11212b7

charles-zablit mentioned this pull request Jun 17, 2025

move NodePrinter declarations to a header #82303

Closed

add range tracking when demangling a name

51fd790

charles-zablit force-pushed the charles-zablit/mangling branch from c95ffe3 to 51fd790 Compare June 17, 2025 16:33

Michael137 reviewed Jun 18, 2025

View reviewed changes

charles-zablit mentioned this pull request Jun 18, 2025

[swift][Demangling][NFC] Move NodePrinter declarations to a header #82335

Open

charles-zablit closed this Jun 18, 2025

	/// \param MangledName The mangled symbol string, which start a mangling
	/// \param MangledName The mangled symbol string, which start with a mangling

add range tracking when demangling a name #82298

add range tracking when demangling a name #82298

Uh oh!

Conversation

charles-zablit commented Jun 17, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Motivation

Implementation details

Original implementation

Current implementation

Testing (removed, relevant only for the original implementation)

Follow ups

Uh oh!

adrian-prantl commented Jun 17, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Michael137 left a comment

Choose a reason for hiding this comment

Uh oh!

Michael137 commented Jun 18, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

charles-zablit commented Jun 18, 2025

Uh oh!

Uh oh!

charles-zablit commented Jun 17, 2025 •

edited

Loading