[lldb][Expression] Make __lldb_expr function qualifiers match source context by Michael137 · Pull Request #177922 · llvm/llvm-project

Michael137 · 2026-01-26T10:16:50Z

We stopped marking __lldb_expr with the function qualifiers of the method LLDB is stopped in ever since 8bdcd522510f923185cdfaec66c4a78d0a0d38c0. The assumption was that it wasn't ever required for correctness (i.e., LLDB should just always pretend it's in a mutable context). But since function qualifiers affect overloading in C++, this assumption can lead to unexpected expression evaluator behaviour. E.g., if a function is overloaded on qualifiers (const vs. non-const), the expression evaluator would currently always call the non-CV qualified overload.

This patch adds function qualifiers to $__lldb_class::$__lldb_expr that resemble the qualifiers of the method that we're stopped in.

However, mutating variables or calling arbitrary member functions from CV-qualified methods can be useful/is something users already may be used to. To provide users with the ability to ignore the CV-qualifiers of the current context, we will provide an expression evaluator flag that switches this off in a follow-up patch.

github-actions · 2026-01-26T10:24:45Z

🐧 Linux x64 Test Results

33303 tests passed
511 tests skipped

✅ The build succeeded and all tests passed.

llvmbot · 2026-01-26T10:44:45Z

@llvm/pr-subscribers-lldb

Author: Michael Buch (Michael137)

Changes

This was originally removed in 8bdcd522510f923185cdfaec66c4a78d0a0d38c0 under the assumption this wasn't required (i.e., LLDB should just always pretend it's in a mutable context). But since function qualifiers affect overloading in C++, this assumption can lead to unexpected expression evaluator behaviour. Instead, in this patch we try to add function qualifiers to $__lldb_class::$__lldb_expr that resemble the qualifiers in the method that we're stopped in.

However, mutating variables or calling arbitrary member functions from CV-qualified methods can be useful/is something users already may be used to. To provide users with the ability to ignore the CV-qualifiers of the current context, we will provide an expression evaluator flag that switches this off in a follow-up patch.

Patch is 37.45 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/177922.diff

26 Files Affected:

(modified) lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp (+7-1)
(modified) lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp (+34-9)
(modified) lldb/test/API/commands/expression/expr_inside_lambda/TestExprInsideLambdas.py (+2-2)
(modified) lldb/test/API/lang/cpp/const_this/TestConstThis.py (+4-6)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/Makefile (+3)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/TestExprInConstMethod.py (+106)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/main.cpp (+49)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/Makefile (+3)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/TestExprInConstVolatileMethod.py (+60)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/main.cpp (+43)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/Makefile (+3)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/TestExprOnCVQualifiedObjects.py (+21)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/main.cpp (+25)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/fixit/Makefile (+3)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/fixit/TestExprInConstMethodWithFixit.py (+42)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/fixit/main.cpp (+22)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/non_const_method/Makefile (+3)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/non_const_method/TestExprInNonConstMethod.py (+85)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/non_const_method/main.cpp (+49)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/template_const_method/Makefile (+3)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/template_const_method/TestExprInTemplateConstMethod.py (+106)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/template_const_method/main.cpp (+51)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/template_non_const_method/Makefile (+3)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/template_non_const_method/TestExprInTemplateNonConstMethod.py (+85)
(added) lldb/test/API/lang/cpp/expression-context-qualifiers/template_non_const_method/main.cpp (+49)
(modified) lldb/test/API/lang/cpp/this/TestCPPThis.py (+9-3)

diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
index 24a5dc5362964..41d2d2cb23146 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
@@ -844,6 +844,12 @@ void ClangExpressionDeclMap::LookUpLldbClass(NameSearchContext &context) {
 
     QualType class_qual_type = m_ast_context->getCanonicalTagType(class_decl);
 
+    // The synthesized __lldb_expr will adopt the qualifiers from this class
+    // type. Make sure we use the qualifiers of the method that we're currently
+    // stopped in.
+    class_qual_type.addFastQualifiers(
+        method_decl->getMethodQualifiers().getFastQualifiers());
+
     TypeFromUser class_user_type(
         class_qual_type.getAsOpaquePtr(),
         function_decl_ctx.GetTypeSystem()->weak_from_this());
@@ -1991,7 +1997,7 @@ void ClangExpressionDeclMap::AddContextClassType(NameSearchContext &context,
     std::array<CompilerType, 1> args{void_clang_type.GetPointerType()};
 
     CompilerType method_type = m_clang_ast_context->CreateFunctionType(
-        void_clang_type, args, false, 0);
+        void_clang_type, args, false, ut.GetTypeQualifiers());
 
     const bool is_virtual = false;
     const bool is_static = false;
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
index cfe187ffc4114..ca4199faa3841 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
@@ -10,6 +10,7 @@
 
 #include "ClangExpressionUtil.h"
 
+#include "clang/AST/TypeBase.h"
 #include "clang/Basic/CharInfo.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
@@ -189,6 +190,28 @@ static void AddMacros(const DebugMacros *dm, CompileUnit *comp_unit,
   }
 }
 
+/// Return qualifers of the current C++ method.
+static clang::Qualifiers GetFrameCVQualifiers(StackFrame *frame) {
+  if (!frame)
+    return {};
+
+  auto this_sp = frame->FindVariable(ConstString("this"));
+  if (!this_sp)
+    return {};
+
+  // Lambdas that capture 'this' have a member variable called 'this'. The class
+  // context of __lldb_expr for a lambda is the class type of the 'this' capture
+  // (not the anonymous lambda structure). So use the qualifiers of the captured
+  // 'this'.
+  if (auto this_this_sp = this_sp->GetChildMemberWithName("this"))
+    return clang::Qualifiers::fromCVRMask(
+        this_this_sp->GetCompilerType().GetPointeeType().GetTypeQualifiers());
+
+  // Not in a lambda. Return 'this' qualifiers.
+  return clang::Qualifiers::fromCVRMask(
+      this_sp->GetCompilerType().GetPointeeType().GetTypeQualifiers());
+}
+
 lldb_private::ClangExpressionSourceCode::ClangExpressionSourceCode(
     llvm::StringRef filename, llvm::StringRef name, llvm::StringRef prefix,
     llvm::StringRef body, Wrapping wrap, WrapKind wrap_kind)
@@ -463,15 +486,17 @@ bool ClangExpressionSourceCode::GetText(
                          lldb_local_var_decls.GetData(), tagged_body.c_str());
       break;
     case WrapKind::CppMemberFunction:
-      wrap_stream.Printf("%s"
-                         "void                                   \n"
-                         "$__lldb_class::%s(void *$__lldb_arg)   \n"
-                         "{                                      \n"
-                         "    %s;                                \n"
-                         "%s"
-                         "}                                      \n",
-                         module_imports.c_str(), m_name.c_str(),
-                         lldb_local_var_decls.GetData(), tagged_body.c_str());
+      wrap_stream.Printf(
+          "%s"
+          "void                                    \n"
+          "$__lldb_class::%s(void *$__lldb_arg) %s \n"
+          "{                                       \n"
+          "    %s;                                 \n"
+          "%s"
+          "}                                       \n",
+          module_imports.c_str(), m_name.c_str(),
+          GetFrameCVQualifiers(exe_ctx.GetFramePtr()).getAsString().c_str(),
+          lldb_local_var_decls.GetData(), tagged_body.c_str());
       break;
     case WrapKind::ObjCInstanceMethod:
       wrap_stream.Printf(
diff --git a/lldb/test/API/commands/expression/expr_inside_lambda/TestExprInsideLambdas.py b/lldb/test/API/commands/expression/expr_inside_lambda/TestExprInsideLambdas.py
index e35cfa6a289a7..0a7683b310f43 100644
--- a/lldb/test/API/commands/expression/expr_inside_lambda/TestExprInsideLambdas.py
+++ b/lldb/test/API/commands/expression/expr_inside_lambda/TestExprInsideLambdas.py
@@ -127,8 +127,8 @@ def test_expr_inside_lambda(self):
 
         # Inside non_capturing_method
         lldbutil.continue_to_breakpoint(process, bkpt)
-        self.expect_expr("local", result_type="int", result_value="5")
-        self.expect_expr("local2", result_type="int", result_value="10")
+        self.expect_expr("local", result_type="const int", result_value="5")
+        self.expect_expr("local2", result_type="const int", result_value="10")
         self.expect_expr("local2 * local", result_type="int", result_value="50")
 
         self.expectExprError(
diff --git a/lldb/test/API/lang/cpp/const_this/TestConstThis.py b/lldb/test/API/lang/cpp/const_this/TestConstThis.py
index 4b7d3aadb62ab..c2df61fde2b58 100644
--- a/lldb/test/API/lang/cpp/const_this/TestConstThis.py
+++ b/lldb/test/API/lang/cpp/const_this/TestConstThis.py
@@ -11,10 +11,9 @@ def run_class_tests(self):
         # Expression not referencing context class.
         self.expect_expr("1 + 1", result_type="int", result_value="2")
         # Referencing context class.
-        # FIXME: This and the expression below should return const types.
-        self.expect_expr("member", result_type="int", result_value="3")
+        self.expect_expr("member", result_type="const int", result_value="3")
         # Check the type of context class.
-        self.expect_expr("this", result_type="ContextClass *")
+        self.expect_expr("this", result_type="const ContextClass *")
 
     def test_member_func(self):
         self.build()
@@ -36,10 +35,9 @@ def run_template_class_tests(self):
         # Expression not referencing context class.
         self.expect_expr("1 + 1", result_type="int", result_value="2")
         # Referencing context class.
-        # FIXME: This and the expression below should return const types.
-        self.expect_expr("member", result_type="int", result_value="4")
+        self.expect_expr("member", result_type="const int", result_value="4")
         # Check the type of context class.
-        self.expect_expr("this", result_type="TemplatedContextClass<int> *")
+        self.expect_expr("this", result_type="const TemplatedContextClass<int> *")
 
     def test_template_member_func(self):
         self.build()
diff --git a/lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/Makefile b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/Makefile
new file mode 100644
index 0000000000000..99998b20bcb05
--- /dev/null
+++ b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/Makefile
@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules
diff --git a/lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/TestExprInConstMethod.py b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/TestExprInConstMethod.py
new file mode 100644
index 0000000000000..0ba6c8a837db4
--- /dev/null
+++ b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/TestExprInConstMethod.py
@@ -0,0 +1,106 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestCase(TestBase):
+    def test(self):
+        self.build()
+        (_, process, _, _) = lldbutil.run_to_source_breakpoint(
+            self, "Break: const_method begin", lldb.SBFileSpec("main.cpp")
+        )
+
+        self.expect_expr("bar()", result_value="2", result_type="int")
+        self.expect(
+            "expression m_const_mem = 2.0",
+            error=True,
+            substrs=[
+                "cannot assign to non-static data member",
+                "with const-qualified type",
+            ],
+        )
+        self.expect(
+            "expression m_mem = 2.0",
+            error=True,
+            substrs=[
+                "cannot assign to non-static data member within const member function"
+            ],
+        )
+        self.expect_expr("((Foo*)this)->bar()", result_type="double", result_value="5")
+
+        lldbutil.continue_to_source_breakpoint(
+            self,
+            process,
+            "Break: const_method no-this lambda",
+            lldb.SBFileSpec("main.cpp"),
+        )
+
+        self.expect(
+            "expression x = 7.0",
+            error=True,
+            substrs=[
+                "cannot assign to non-static data member within const member function"
+            ],
+        )
+
+        lldbutil.continue_to_source_breakpoint(
+            self,
+            process,
+            "Break: const_method mutable no-this lambda",
+            lldb.SBFileSpec("main.cpp"),
+        )
+
+        self.expect_expr("x = 7.0")
+        self.expect_expr("x", result_value="7")
+
+        lldbutil.continue_to_source_breakpoint(
+            self, process, "Break: const_method lambda", lldb.SBFileSpec("main.cpp")
+        )
+
+        # FIXME: mutating this capture should be disallowed in a non-mutable lambda.
+        self.expect_expr("y = 8.0")
+        self.expect_expr("bar()", result_value="2", result_type="int")
+        self.expect(
+            "expression m_const_mem = 2.0",
+            error=True,
+            substrs=[
+                "cannot assign to non-static data member",
+                "with const-qualified type",
+            ],
+        )
+        self.expect(
+            "expression m_mem = 2.0",
+            error=True,
+            substrs=[
+                "cannot assign to non-static data member within const member function"
+            ],
+        )
+        self.expect_expr("m_mem", result_value="-2")
+        self.expect_expr("((Foo*)this)->bar()", result_type="double", result_value="5")
+
+        lldbutil.continue_to_source_breakpoint(
+            self,
+            process,
+            "Break: const_method mutable lambda",
+            lldb.SBFileSpec("main.cpp"),
+        )
+
+        self.expect_expr("y = 9.0")
+        self.expect_expr("bar()", result_value="2", result_type="int")
+        self.expect(
+            "expression m_const_mem = 2.0",
+            error=True,
+            substrs=[
+                "cannot assign to non-static data member",
+                "with const-qualified type",
+            ],
+        )
+        self.expect(
+            "expression m_mem = 2.0",
+            error=True,
+            substrs=[
+                "cannot assign to non-static data member within const member function"
+            ],
+        )
+        self.expect_expr("m_mem", result_value="-2")
diff --git a/lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/main.cpp b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/main.cpp
new file mode 100644
index 0000000000000..7cb74767b458a
--- /dev/null
+++ b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_method/main.cpp
@@ -0,0 +1,49 @@
+#include <cassert>
+#include <cstdio>
+
+struct Foo {
+  double bar() { return 5.0; }
+
+  int bar() const { return 2; }
+
+  int const_method() const {
+    auto x = bar();
+    assert(x == 2);
+    std::puts("Break: const_method begin");
+
+    [x] {
+      std::puts("Keep on multiple lines...");
+      std::puts("Break: const_method no-this lambda");
+    }();
+
+    [x]() mutable {
+      std::puts("Keep on multiple lines...");
+      std::puts("Break: const_method mutable no-this lambda");
+    }();
+
+    [this, y = x] {
+      auto x = bar() + y;
+      std::puts("Break: const_method lambda");
+    }();
+
+    [this, y = x]() mutable {
+      auto x = bar() + y;
+      std::puts("Break: const_method mutable lambda");
+    }();
+
+    return 120;
+  }
+
+  float m_mem = -2.0;
+  const float m_const_mem = -3.0;
+};
+
+int main() {
+  const Foo f;
+  f.bar();
+
+  Foo f2;
+  f2.bar();
+
+  return Foo{}.const_method();
+}
diff --git a/lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/Makefile b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/Makefile
new file mode 100644
index 0000000000000..99998b20bcb05
--- /dev/null
+++ b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/Makefile
@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules
diff --git a/lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/TestExprInConstVolatileMethod.py b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/TestExprInConstVolatileMethod.py
new file mode 100644
index 0000000000000..f20b9d8164841
--- /dev/null
+++ b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/TestExprInConstVolatileMethod.py
@@ -0,0 +1,60 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestCase(TestBase):
+    def test(self):
+        self.build()
+        (_, process, _, _) = lldbutil.run_to_source_breakpoint(
+            self, "Break here: const", lldb.SBFileSpec("main.cpp")
+        )
+
+        self.expect_expr("bar()", result_type="double", result_value="5")
+        self.expect_expr("const_volatile_method()")
+        self.expect_expr("const_method()")
+        self.expect(
+            "expression volatile_method()",
+            error=True,
+            substrs=["has type 'const Foo'", "but function is not marked const"],
+        )
+
+        lldbutil.continue_to_source_breakpoint(
+            self, process, "Break here: volatile", lldb.SBFileSpec("main.cpp")
+        )
+
+        self.expect_expr(
+            "bar()", result_type="const char *", result_summary='"volatile_bar"'
+        )
+        self.expect_expr("const_volatile_method()")
+        self.expect(
+            "expression const_method()",
+            error=True,
+            substrs=["has type 'volatile Foo'", "but function is not marked volatile"],
+        )
+        self.expect_expr("volatile_method()")
+
+        lldbutil.continue_to_source_breakpoint(
+            self, process, "Break here: const volatile", lldb.SBFileSpec("main.cpp")
+        )
+
+        self.expect_expr("bar()", result_type="int", result_value="2")
+        self.expect_expr("other_cv_method()")
+
+        self.expect(
+            "expression const_method()",
+            error=True,
+            substrs=[
+                "has type 'const volatile Foo'",
+                "but function is not marked const or volatile",
+            ],
+        )
+        self.expect(
+            "expression volatile_method()",
+            error=True,
+            substrs=[
+                "has type 'const volatile Foo'",
+                "but function is not marked const or volatile",
+            ],
+        )
diff --git a/lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/main.cpp b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/main.cpp
new file mode 100644
index 0000000000000..da0f7e7d1be95
--- /dev/null
+++ b/lldb/test/API/lang/cpp/expression-context-qualifiers/const_volatile_method/main.cpp
@@ -0,0 +1,43 @@
+#include <cassert>
+#include <cstdio>
+
+struct Foo {
+  double bar() const { return 5.0; }
+  const char *bar() volatile { return "volatile_bar"; }
+  int bar() volatile const { return 2; }
+
+  int volatile_method() volatile {
+    std::puts("Break here: volatile");
+    return 0;
+  }
+  int const_method() const {
+    std::puts("Break here: const");
+    return 0;
+  }
+  int other_cv_method() const volatile { return 20; }
+
+  int const_volatile_method() const volatile {
+    auto x = bar();
+    assert(x == 2);
+    other_cv_method();
+
+    std::puts("Break here: const volatile");
+
+    return 120;
+  }
+};
+
+int main() {
+  const Foo f;
+  f.bar();
+  f.const_method();
+
+  volatile Foo f2;
+  f2.bar();
+  f2.volatile_method();
+
+  const volatile Foo f3;
+  f3.bar();
+
+  return Foo{}.const_volatile_method();
+}
diff --git a/lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/Makefile b/lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/Makefile
new file mode 100644
index 0000000000000..99998b20bcb05
--- /dev/null
+++ b/lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/Makefile
@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules
diff --git a/lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/TestExprOnCVQualifiedObjects.py b/lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/TestExprOnCVQualifiedObjects.py
new file mode 100644
index 0000000000000..0f661471df749
--- /dev/null
+++ b/lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/TestExprOnCVQualifiedObjects.py
@@ -0,0 +1,21 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestCase(TestBase):
+    def test(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(
+            self,
+            "Break here",
+            lldb.SBFileSpec("main.cpp"),
+        )
+
+        self.expect_expr("f.bar()", result_type="double", result_value="5")
+        self.expect_expr("cf.bar()", result_type="int", result_value="2")
+        self.expect_expr("vf.bar()", result_type="short", result_value="8")
+        self.expect_expr(
+            "cvf.bar()", result_type="const char *", result_summary='"volatile"'
+        )
diff --git a/lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/main.cpp b/lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/main.cpp
new file mode 100644
index 0000000000000..eb7f8b82f2695
--- /dev/null
+++ b/lldb/test/API/lang/cpp/expression-context-qualifiers/cv_qualified_objects/main.cpp
@@ -0,0 +1,25 @@
+#include <cstdio>
+
+struct Foo {
+  double bar() { return 5.0; }
+  int bar() const { return 2; }
+  short bar() volatile { return 8; }
+  char const *bar() const volatile { return "volatile"; }
+
+  float m_mem = -2.0;
+  const float m_const_mem = -3.0;
+};
+
+int main() {
+  Foo f;
+  const Foo cf;
+  volatile Foo vf;
+  const volatile Foo cvf;
+
+  f.bar();
+  cf.bar();
+  vf.bar();
+  cvf.bar();
+
+  std::puts("Break here");
+}
diff --git a/lldb/test/API/lang/cpp/expression-context-qualifiers/fixit/Makefile b/lldb/test/API/lang/cpp/expression-context-qualifiers/fixit/Makefile
new file mode 100644
index 0000000000000..99998b20bcb05
--- /dev/null
+++ b/lldb/test/API/lang/cpp/expression-context-qualifiers/fixit/Makefile
@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules
diff --git a/lldb/test/API/lang/cpp/expression-context-qualifiers/fixit/TestExprInConstMethodWithFixit.py b/lldb/test/API/lang/cpp/expression-context-qualifiers/fixit/TestExprInConstMethodWithFixit.py
new file mode 100644
index 0000000000000..3c239c89d0ca7
--- /dev/null
+++ b/lldb/test/API/lang/cpp/expression-context-qualifiers/fixit/TestExprInConstMethodWithFixit.py
@@ -0,0 +1,42 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestCase(TestBase):
+    def test(self):
+        self.build()
+        (_, process, _, _) = lldbutil.run_to_source_breakpoint(
+            self, "Break here", lldb.SBFileSpec("main.cpp")
+        )
+
+        self.expect(
+            "expression m_bar->method()",
+            error=True,
+            substrs=[
+                "member reference type 'const Bar' is not a pointer",
+                "but function is not marked const",
+            ],
+        )
+
+        # Two fix-its
+        self.expect(
+            "expression -- m_ba...
[truncated]

…ption Depends on: * llvm#177920 * llvm#177922 In llvm#177922 we make expressions run in C++ member functions honor the function qualifiers of the current stop context. E.g., this means we can no longer run non-const member functions when stopped in a const-member function. To ensure users can still do this if they really need/want to, we provide an option to not honor the qualifiers at all, leaving the `__lldb_expr` as the least qualified, allowing it to call any function/mutate any members.

adrian-prantl · 2026-01-26T17:16:46Z

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp

-                         "}                                      \n",
-                         module_imports.c_str(), m_name.c_str(),
-                         lldb_local_var_decls.GetData(), tagged_body.c_str());
+      wrap_stream.Printf(


Side note: I was always puzzled why we use Printf format strings here. It would seem that << operations would be more readable and we could avoid the c_str() conversions that recompute the length of the strings?

Yea we could definitely do that. Probably best as a separate clean-up?

adrian-prantl · 2026-01-26T17:17:55Z

...ang/cpp/expression-context-qualifiers/const_volatile_method/TestExprInConstVolatileMethod.py

+        self.expect_expr("const_method()")
+        self.expect(
+            "expression volatile_method()",
+            error=True,


why can this not be expect_expr?

expect_expr asserts that the expression succeeded. So if we want to expect that an expression failed, we have to resort to expect

…ption Depends on: * llvm#177920 * llvm#177922 In llvm#177922 we make expressions run in C++ member functions honor the function qualifiers of the current stop context. E.g., this means we can no longer run non-const member functions when stopped in a const-member function. To ensure users can still do this if they really need/want to, we provide an option to not honor the qualifiers at all, leaving the `__lldb_expr` as the least qualified, allowing it to call any function/mutate any members.

…context This was originally removed in `8bdcd522510f923185cdfaec66c4a78d0a0d38c0` under the assumption this wasn't required (i.e., LLDB should just always pretend it's in a mutable context). But since function qualifiers affect overloading in C++, this assumption can lead to unexpected expression evaluator behaviour. Instead, in this patch we try to add function qualifiers to `$__lldb_class::$__lldb_expr` that resemble the qualifiers in the method that we're stopped in.

…ption Depends on: * llvm#177920 * llvm#177922 In llvm#177922 we make expressions run in C++ member functions honor the function qualifiers of the current stop context. E.g., this means we can no longer run non-const member functions when stopped in a const-member function. To ensure users can still do this if they really need/want to, we provide an option to not honor the qualifiers at all, leaving the `__lldb_expr` as the least qualified, allowing it to call any function/mutate any members.

Michael137 requested review from adrian-prantl and jimingham January 26, 2026 10:16

Michael137 force-pushed the lldb/const-expr-3 branch from 2122824 to 8a290ca Compare January 26, 2026 10:40

Michael137 marked this pull request as ready for review January 26, 2026 10:44

Michael137 requested a review from JDevlieghere as a code owner January 26, 2026 10:44

llvmbot added the lldb label Jan 26, 2026

Michael137 force-pushed the lldb/const-expr-3 branch from 8a290ca to d6d51a9 Compare January 26, 2026 10:48

Michael137 mentioned this pull request Jan 26, 2026

[lldb][Expression] Add --cpp-ignore-context-qualifiers expression evaluation option #177926

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Michael137 force-pushed the lldb/const-expr-3 branch from d6d51a9 to 2aa343f Compare January 26, 2026 11:34

Michael137 force-pushed the lldb/const-expr-3 branch from 2aa343f to 96aa898 Compare January 26, 2026 13:17

adrian-prantl reviewed Jan 26, 2026

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adrian-prantl approved these changes Feb 4, 2026

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Michael137 force-pushed the lldb/const-expr-3 branch from 96aa898 to 616054e Compare February 4, 2026 23:24

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[lldb][Expression] Make __lldb_expr function qualifiers match source context#177922

[lldb][Expression] Make __lldb_expr function qualifiers match source context#177922
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