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Return a SwiftArrayEmptyBufferHandler if loc points to an EmptyArray Symbol. #10920

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Return a SwiftArrayEmptyBufferHandler if loc points to an EmptyArray Symbol. #10920

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16 changes: 16 additions & 0 deletions lldb/source/Plugins/Language/Swift/SwiftArray.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
#include "Plugins/LanguageRuntime/Swift/SwiftLanguageRuntime.h"
#include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
#include "Plugins/TypeSystem/Swift/TypeSystemSwiftTypeRef.h"
#include "lldb/Core/Address.h"
#include "lldb/DataFormatters/FormattersHelpers.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/Target.h"
Expand Down Expand Up @@ -460,6 +461,21 @@ SwiftArrayBufferHandler::CreateBufferHandler(ValueObject &static_valobj) {
lldb::addr_t storage_location =
buffer_sp->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);

lldb_private::Address addr = Address();
addr.SetLoadAddress(storage_location, exe_ctx.GetTargetPtr());

// If the storage_location points to a swiftEmptyArrayStorage symbol, return
// a SwiftArrayEmptyBufferHandler.
if (auto *symbol = addr.CalculateSymbolContextSymbol()) {
auto mangledName = symbol->GetMangled().GetMangledName().GetStringRef();
if (mangledName == "$ss19__EmptyArrayStorageCN") {
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should this be _swiftEmptyArrayStorage?

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I am checking the mangled name:

> xcrun swift-demangle ss19__EmptyArrayStorageCN 
$ss19__EmptyArrayStorageCN ---> type metadata for Swift.__EmptyArrayStorage

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When I inspect an empty array, I see:

(lldb) v -R -T -d no-dynamic-values
(Swift.Array<main.P>) x = {
  (Swift._ArrayBuffer<main.P>) _buffer = {
    (Swift._BridgeStorage<Swift.__ContiguousArrayStorageBase>) _storage = {
      (Builtin.BridgeObject) rawValue = 0x00000001f52cd120 _swiftEmptyArrayStorage
    }
  }
}

I don't see where $ss19__EmptyArrayStorageCN comes into play. Also the PR description mentions _swiftEmptyArrayStorage but the changed code does not.

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This mangled name is for the type metadata for Swift.__EmptyArrayStorage.

  1. You probably want to match against Swift.__EmptyArrayStorage itself.
  2. Instead of depending on the mangling it would be better to use the helpers in SwiftDemangling.h to make sure you have the expected demangle tree for a class with the right name in STDLIB_MODULENAME.

CompilerType elem_type(
valobj.GetCompilerType().GetArrayElementType(exe_scope));
return std::unique_ptr<SwiftArrayBufferHandler>(
new SwiftArrayEmptyBufferHandler(elem_type));
}
}

if (storage_location != LLDB_INVALID_ADDRESS) {
ProcessSP process_sp(valobj.GetProcessSP());
if (!process_sp)
Expand Down
3 changes: 3 additions & 0 deletions lldb/test/API/lang/swift/swift_empty_arr/Makefile
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@@ -0,0 +1,3 @@
SWIFT_SOURCES := main.swift

include Makefile.rules
17 changes: 17 additions & 0 deletions lldb/test/API/lang/swift/swift_empty_arr/TestSwiftGlobalEmptyArray.py
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@@ -0,0 +1,17 @@
import lldb
from lldbsuite.test.decorators import *
import lldbsuite.test.lldbtest as lldbtest
import lldbsuite.test.lldbutil as lldbutil


class TestSwiftGlobalEmptyArray(lldbtest.TestBase):
@swiftTest
def test(self):
"""Test that printing a global swift array of type SwiftEmptyArrayStorage uses the correct data formatter"""

self.build()
filespec = lldb.SBFileSpec("main.swift")
target, process, thread, breakpoint1 = lldbutil.run_to_source_breakpoint(
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Suggested change
target, process, thread, breakpoint1 = lldbutil.run_to_source_breakpoint(
lldbutil.run_to_source_breakpoint(

self, "break here", filespec
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Suggested change
self, "break here", filespec
self, "break here", lldb.SBFileSpec("main.swift")

)
self.expect("p x", substrs=["([a.P]) 0 values {}"])
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for tests we use frame var or expr to be explicit whether it's use expression evaluation or not.

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Even better would be

x = self.frame().FindVariable("x")
lldbutil.check_variable(self, x, summary="0 values")

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or self.assertEqual(x.GetSummary(), "0 values")

8 changes: 8 additions & 0 deletions lldb/test/API/lang/swift/swift_empty_arr/main.swift
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@@ -0,0 +1,8 @@
protocol P {}

func go() {
let x: [any P] = []
print("break here")
}

go()