Author: Michael Buch
Date: 2025-10-17T23:27:57+01:00
New Revision: bf2d84db8e95cf0dbf782f6609b034427ab1c07d

URL: 
https://github.com/llvm/llvm-project/commit/bf2d84db8e95cf0dbf782f6609b034427ab1c07d
DIFF: 
https://github.com/llvm/llvm-project/commit/bf2d84db8e95cf0dbf782f6609b034427ab1c07d.diff

LOG: [lldb][ObjC] Consult Objective-C runtime decl vendor when completing type 
(#164011)

(Note, this upstreams code that has been deployed on Apple's Swift LLDB
for many years at this point).

When a `ValueObject` computes its "complete type"
(`MaybeCalculateCompleteType`), it gives the language runtimes a chance
to override the type known to it. The current implementation of
`ObjCLanguageRuntime::GetRuntimeType`, however, didn't consult the
`AppleObjCDeclVendor` to look for types.

As demonstrated in the attached test, when we don't have debug-info for
a base class type (most commonly happens when inheriting from system
framework types) we would not be able to deduce ivars of that type.
However, the runtime knows about the ivars, so we should be able to
retrieve them.

There's still a couple of caveats for future follow-up/investigation:
1. `frame var` isn't able to access such backing ivars explicitly (even
if they do exist)
2. When compiling with `-gmodules`, LLDB gets confused about what is
correct source of information for these decls is.

rdar://162069497

Added: 
    lldb/test/API/lang/objc/ivar-in-framework-base/Makefile
    lldb/test/API/lang/objc/ivar-in-framework-base/TestIvarInFrameworkBase.py
    lldb/test/API/lang/objc/ivar-in-framework-base/lib.h
    lldb/test/API/lang/objc/ivar-in-framework-base/lib.m
    lldb/test/API/lang/objc/ivar-in-framework-base/main.m

Modified: 
    lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.cpp
    lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h

Removed: 
    


################################################################################
diff  --git a/lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.cpp 
b/lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.cpp
index c33760eccd127..2b2ca080c7f55 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.cpp
@@ -423,6 +423,46 @@ Status 
ObjCLanguageRuntime::ObjCExceptionPrecondition::ConfigurePrecondition(
   return error;
 }
 
+CompilerType ObjCLanguageRuntime::LookupInModulesVendor(ConstString class_name,
+                                                        Target &target) {
+  assert(class_name);
+
+  auto *persistent_state = llvm::cast<ClangPersistentVariables>(
+      target.GetPersistentExpressionStateForLanguage(lldb::eLanguageTypeC));
+  if (!persistent_state)
+    return {};
+
+  auto clang_modules_decl_vendor_sp =
+      persistent_state->GetClangModulesDeclVendor();
+  if (!clang_modules_decl_vendor_sp)
+    return {};
+
+  auto types = clang_modules_decl_vendor_sp->FindTypes(
+      class_name, /*max_matches*/ UINT32_MAX);
+  if (types.empty())
+    return {};
+
+  return types.front();
+}
+
+CompilerType ObjCLanguageRuntime::LookupInRuntime(ConstString class_name) {
+  auto *runtime_vendor = GetDeclVendor();
+  if (!runtime_vendor)
+    return {};
+
+  std::vector<CompilerDecl> compiler_decls;
+  runtime_vendor->FindDecls(class_name, false, UINT32_MAX, compiler_decls);
+  if (compiler_decls.empty())
+    return {};
+
+  auto *ctx =
+      llvm::dyn_cast<TypeSystemClang>(compiler_decls[0].GetTypeSystem());
+  if (!ctx)
+    return {};
+
+  return ctx->GetTypeForDecl(compiler_decls[0].GetOpaqueDecl());
+}
+
 std::optional<CompilerType>
 ObjCLanguageRuntime::GetRuntimeType(CompilerType base_type) {
   CompilerType class_type;
@@ -442,18 +482,21 @@ ObjCLanguageRuntime::GetRuntimeType(CompilerType 
base_type) {
   if (!class_name)
     return std::nullopt;
 
-  TypeSP complete_objc_class_type_sp = LookupInCompleteClassCache(class_name);
-  if (!complete_objc_class_type_sp)
-    return std::nullopt;
-
-  CompilerType complete_class(
-      complete_objc_class_type_sp->GetFullCompilerType());
-  if (complete_class.GetCompleteType()) {
-    if (is_pointer_type)
-      return complete_class.GetPointerType();
-    else
-      return complete_class;
+  if (TypeSP complete_objc_class_type_sp =
+          LookupInCompleteClassCache(class_name)) {
+    if (CompilerType complete_class =
+            complete_objc_class_type_sp->GetFullCompilerType();
+        complete_class.GetCompleteType())
+      return is_pointer_type ? complete_class.GetPointerType() : 
complete_class;
   }
 
+  assert(m_process);
+  if (CompilerType found =
+          LookupInModulesVendor(class_name, m_process->GetTarget()))
+    return is_pointer_type ? found.GetPointerType() : found;
+
+  if (CompilerType found = LookupInRuntime(class_name))
+    return is_pointer_type ? found.GetPointerType() : found;
+
   return std::nullopt;
 }

diff  --git a/lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h 
b/lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h
index 45de098c15f51..cc8281e9d1a02 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h
@@ -465,6 +465,10 @@ class ObjCLanguageRuntime : public LanguageRuntime {
 
   ObjCLanguageRuntime(const ObjCLanguageRuntime &) = delete;
   const ObjCLanguageRuntime &operator=(const ObjCLanguageRuntime &) = delete;
+
+private:
+  CompilerType LookupInRuntime(ConstString class_name);
+  CompilerType LookupInModulesVendor(ConstString class_name, Target &process);
 };
 
 } // namespace lldb_private

diff  --git a/lldb/test/API/lang/objc/ivar-in-framework-base/Makefile 
b/lldb/test/API/lang/objc/ivar-in-framework-base/Makefile
new file mode 100644
index 0000000000000..c7947fc138c18
--- /dev/null
+++ b/lldb/test/API/lang/objc/ivar-in-framework-base/Makefile
@@ -0,0 +1,6 @@
+OBJC_SOURCES := main.m lib.m
+LD_EXTRAS = -framework Foundation
+
+include Makefile.rules
+
+lib.o: CFLAGS = $(CFLAGS_NO_DEBUG)

diff  --git 
a/lldb/test/API/lang/objc/ivar-in-framework-base/TestIvarInFrameworkBase.py 
b/lldb/test/API/lang/objc/ivar-in-framework-base/TestIvarInFrameworkBase.py
new file mode 100644
index 0000000000000..40fc6b7a68995
--- /dev/null
+++ b/lldb/test/API/lang/objc/ivar-in-framework-base/TestIvarInFrameworkBase.py
@@ -0,0 +1,39 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestIvarInFrameworkBase(TestBase):
+    """
+    Tests whether LLDB's data inspection commands can correctly retrieve
+    information about ivars from the Objective-C runtime.
+    In this test-case we have a base class type for which we don't have access
+    to the debug-info of the implementation (mimicking the scenario of 
subclassing
+    a type from a system framework). LLDB won't be able to see the backing 
ivar for
+    'fooProp' from just debug-info, but it will fall back on the runtime to 
get the
+    necessary information.
+    """
+
+    def test_frame_var(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "break here", 
lldb.SBFileSpec("main.m"))
+        self.expect("frame variable *bar", substrs=["_fooProp = 10", "_barProp 
= 15"])
+
+    def test_expr(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "break here", 
lldb.SBFileSpec("main.m"))
+        self.expect_expr(
+            "*bar",
+            result_type="Bar",
+            result_children=[
+                ValueCheck(
+                    name="Foo",
+                    children=[
+                        ValueCheck(name="NSObject"),
+                        ValueCheck(name="_fooProp", value="10"),
+                    ],
+                ),
+                ValueCheck(name="_barProp", value="15"),
+            ],
+        )

diff  --git a/lldb/test/API/lang/objc/ivar-in-framework-base/lib.h 
b/lldb/test/API/lang/objc/ivar-in-framework-base/lib.h
new file mode 100644
index 0000000000000..31ceb53dc6885
--- /dev/null
+++ b/lldb/test/API/lang/objc/ivar-in-framework-base/lib.h
@@ -0,0 +1,6 @@
+#import <Foundation/Foundation.h>
+
+@interface Foo : NSObject
+@property int fooProp;
+- (id)init;
+@end

diff  --git a/lldb/test/API/lang/objc/ivar-in-framework-base/lib.m 
b/lldb/test/API/lang/objc/ivar-in-framework-base/lib.m
new file mode 100644
index 0000000000000..e1bf80ac4bd4c
--- /dev/null
+++ b/lldb/test/API/lang/objc/ivar-in-framework-base/lib.m
@@ -0,0 +1,8 @@
+#import "lib.h"
+
+@implementation Foo
+- (id)init {
+  self.fooProp = 10;
+  return self;
+}
+@end

diff  --git a/lldb/test/API/lang/objc/ivar-in-framework-base/main.m 
b/lldb/test/API/lang/objc/ivar-in-framework-base/main.m
new file mode 100644
index 0000000000000..1fd352ec92c54
--- /dev/null
+++ b/lldb/test/API/lang/objc/ivar-in-framework-base/main.m
@@ -0,0 +1,22 @@
+#import "lib.h"
+#include <stdio.h>
+
+@interface Bar : Foo
+@property int barProp;
+- (id)init;
+@end
+
+@implementation Bar
+
+- (id)init {
+  self = [super init];
+  self.barProp = 15;
+  return self;
+}
+@end
+
+int main() {
+  Bar *bar = [Bar new];
+  puts("break here");
+  return 0;
+}


        
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