[lldb] Adopt new pointer and mangled typename based stringForPrintObject #11916

kastiglione · 2025-12-03T00:00:43Z

Adopt stringForPrintObject(_:mangledTypeName:), an overload added in swiftlang/swift#84742.

This new overload allows lldb to call stringForPrintObject using only a pointer referencing the value, and the mangled typename corresponding to the value. The resulting expression does not reference the concrete type.

By not referencing a value's type, po can be performed on variables (and their nested stored properties) without loading the modules corresponding to the value's type. This will improve performance and reliability of po.

rdar://158968103

Adopt `stringForPrintObject(_:mangledTypeName:)`, an overload added in swiftlang/swift#84742. This new overload allows lldb to call `stringForPrintObject` using only a pointer referencing the value, and the mangled typename corresponding to the value. The resulting expression does not reference the concrete type. By not referencing a value's type, `po` can be performed on variables (and their nested stored properties) without loading the modules corresponding to the value's type. This will improve performance and reliability of `po`.

kastiglione · 2025-12-03T00:00:45Z

@swift-ci test

kastiglione · 2025-12-03T00:02:23Z

Draft mode: follow up will include experimental setting, and tests.

kastiglione · 2025-12-03T00:06:05Z

@swift-ci test

kastiglione · 2025-12-03T06:38:12Z

@swift-ci test macOS

kastiglione · 2025-12-03T16:42:17Z

Existing tests all pass with new po.

kastiglione · 2025-12-03T23:38:58Z

@swift-ci test

lldb/source/Target/TargetProperties.td

lldb/source/Plugins/ExpressionParser/Swift/SwiftExpressionSourceCode.cpp

lldb/source/Plugins/LanguageRuntime/Swift/SwiftLanguageRuntime.cpp

adrian-prantl · 2025-12-03T23:54:36Z

...est/API/lang/swift/po/pointer_and_mangled_typename/TestSwiftPrintObjectPointerAndTypeName.py

+        )
+        self.expect("po value", substrs=["2025"])
+        self._filecheck("INT")
+        # CHECK-INT: stringForPrintObject(UnsafeRawPointer(bitPattern: {{[0-9]+}}), mangledTypeName: "SiD")


Neat test, reusing filecheck this way!

lldb/source/Plugins/LanguageRuntime/Swift/SwiftLanguageRuntime.cpp

lldb/source/Plugins/ExpressionParser/Swift/SwiftExpressionSourceCode.cpp

jimingham · 2025-12-04T22:42:37Z

lldb/source/Plugins/ExpressionParser/Swift/SwiftExpressionSourceCode.cpp

-          llvm::VersionTuple version = process_sp->GetHostOSVersion();
-          os_vers << version.getAsString();
+          auto platform = target->GetPlatform();
+          bool is_simulator = platform->GetPluginName().ends_with("-simulator");


Do we really not have a nicer way to tell if a Platform is a simulator?

There's Triple::isSimulatorEnvironment but it's unclear if that applies here, based on the comment:

// The simulators look like the host OS to Process, but Platform // can get the version out of an environment variable.

jimingham · 2025-12-04T22:45:11Z

lldb/include/lldb/Target/Target.h


  bool GetPreparePlaygroundStubFunctions() const { return m_prepare_playground_stub_functions; }

+  void SetDisableAvailability() { m_disable_availability = true; }


This is an odd set API. It only allows you to set it to true, which the name doesn't really imply?

We usually do:

SetWhatever(bool new_value)

which the name doesn't really imply?

It doesn't? I'm failing to see how it would be interpreted otherwise…

There's no reason for code to call SetDisableAvailability(False), as that is the default. Since there's no reason for it to be called like that, I made the function take no arguments, so that it can be called only one way. This may be different than other bool setters, but I feel it's better prevent it from being mis-called than make it match other setters.

Set means "give some value to this feature" - true or false to "Disabling Ability". If all this API does is "DisableAvailability" then it should be called DisableAvailability(). The "Set" is just confusing and adds nothing.

If there are never any situations where you Disable Availability, then you want to enable it again on the same object, then just having a DisableAvailability API is fine. If you would ever want to turn it back on, then you will need a Set API with a bool input.

Fair, I've added a parameter.

lldb/source/Plugins/LanguageRuntime/Swift/SwiftLanguageRuntime.cpp

jimingham · 2025-12-04T22:50:01Z

lldb/source/Plugins/LanguageRuntime/Swift/SwiftLanguageRuntime.cpp

+  addr_t addr = LLDB_INVALID_ADDRESS;
+  if (flags.Test(eTypeInstanceIsPointer)) {
+    // Objects are pointers.
+    addr = object.GetValueAsUnsigned(LLDB_INVALID_ADDRESS);


This should use GetValueAsAddress.

GetValueAsAddress is on SBValue, I don't see an equivalent on ValueObject.

I'm surprised we don't have a little wrapper for this in ValueObject, but you can do what GetValueAsAddress does, and call FixDataAddress of the addr you get back.

@jasonmolenda will know for sure whether that's the right thing to do.

Yeah if it's guaranteed to be an address it's safe to run it through Process::FixAnyAddress() (the method to use when you don't know if it's an address of code or data). With MTE managed heap, if the value might get put into a jitted expression (so used in code running in the inferior, with MTE) you need to retain the MTE nibble in the top byte. It's an edge case but something to mention, @felipepiovezan dealt with a tricky case where we needed to maintain metadata bits through to the point where we looked it up/use it, just recently, for something that ended up in a jitted expression.

@jasonmolenda thanks, this address is data, and will be used in a jitted expression.

I added a call to FixDataAddress.

kastiglione · 2025-12-09T18:43:46Z

@swift-ci test

adrian-prantl

LGTM with outstanding feedback addressed.

kastiglione · 2025-12-10T21:11:26Z

@swift-ci test

kastiglione · 2025-12-11T01:35:32Z

@jimingham I've replied to your feedback

kastiglione · 2025-12-11T18:44:02Z

@swift-ci test

jimingham

There was one grammatical error in a comment (can the -> can get the).

Other than that, LGTM.

kastiglione · 2025-12-11T19:55:46Z

@swift-ci test

kastiglione · 2025-12-11T19:57:28Z

lldb/source/Plugins/ExpressionParser/Swift/SwiftExpressionParser.cpp

+  if (!m_options.GetUseContextFreeSwiftPrintObject())
+    if (!m_swift_ast_ctx.GetImplicitImports(
+            m_sc, process_sp, additional_imports, implicit_import_error)) {


@adrian-prantl I've introduced this change to the PR. This prevents module loading when the expression is running the new po.

This LGTM, assuming m_options.GetUseContextFreeSwiftPrintObject() is only true in a po!

kastiglione requested a review from a team as a code owner December 3, 2025 00:00

kastiglione marked this pull request as draft December 3, 2025 00:00

Fix missing rename

9cd7c44

kastiglione requested a review from adrian-prantl December 3, 2025 00:21

kastiglione added 2 commits December 3, 2025 10:50

Add setting gating the new po, initially disabled by default

3c969d6

Add tests for new po

caade22

kastiglione marked this pull request as ready for review December 3, 2025 23:38

kastiglione requested review from augusto2112, felipepiovezan and jimingham December 3, 2025 23:45

adrian-prantl reviewed Dec 3, 2025

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augusto2112 approved these changes Dec 4, 2025

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jimingham reviewed Dec 4, 2025

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lldb/source/Plugins/ExpressionParser/Swift/SwiftExpressionSourceCode.cpp Outdated Show resolved Hide resolved

jimingham reviewed Dec 4, 2025

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lldb/source/Plugins/LanguageRuntime/Swift/SwiftLanguageRuntime.cpp Outdated Show resolved Hide resolved

jimingham reviewed Dec 4, 2025

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kastiglione added 3 commits December 9, 2025 10:27

Update names

defe915

Support embedded swift prefix

ff4b066

Update comment about OS version 9999

714c3bb

adrian-prantl approved these changes Dec 9, 2025

View reviewed changes

Move self.build() out of setUp and into the test functions

efa060f

Refactor PrintObjectViaPointer to return Error instead of bool

f6bf6dd

kastiglione added 2 commits December 11, 2025 10:42

Take bool parameter in SetDisableAvailability

d8f6faa

Call FixDataAddress on object addresses

5cb63c4

jimingham approved these changes Dec 11, 2025

View reviewed changes

kastiglione added 3 commits December 11, 2025 11:53

Rename new eval option to its abstraction not its implementation

9442b97

Disable implicit module loading for context-free po

b9e07a3

Fix comment grammar mistake

6f0d8fd

kastiglione commented Dec 11, 2025

View reviewed changes


		bool GetPreparePlaygroundStubFunctions() const { return m_prepare_playground_stub_functions; }

		void SetDisableAvailability() { m_disable_availability = true; }

[lldb] Adopt new pointer and mangled typename based stringForPrintObject #11916

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[lldb] Adopt new pointer and mangled typename based stringForPrintObject #11916

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kastiglione commented Dec 3, 2025 •

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