[clang] fix access checking about function overloading (PR #107768)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Zhikai Zeng (Backl1ght)

<details>
<summary>Changes</summary>

fix https://github.com/llvm/llvm-project/issues/107629

After some more debugging, I find out that we will check access here at https://github.com/llvm/llvm-project/blob/8e010ac5a173c9dee44b44324169a3e100a1a6fc/clang/lib/Sema/SemaInit.cpp#L7807

And for `f()` inside code below, `Found.getAccess()` is `AS_none` hence `CheckAddressOfMemberAccess` return `AR_accessible` directly.

```cpp
struct Base {
public:
  int f(int);
private:
  int f();  // expect-note {{declared private here}}
};

struct Derived : public Base {};

void f() {
  int(Derived::* public_f)(int) = &Derived::f;
  int(Derived::* private_f)() = &Derived::f;  // expect-error {{'f' is a private member of 'Base'}}
}
```

I think the `Found.getAccess()` is intended to be `AS_none` so I just add one more access check for the `UnresolvedLookupExpr` when `Found.getAccess()` is `AS_none`. If add the check unconditionally clang will report lots of duplicate errors and cause several unit tests to fail.

I also test the UB mentioned in https://github.com/llvm/llvm-project/issues/107629 and clang now display 4 `false` as expecetd.

---
Full diff: https://github.com/llvm/llvm-project/pull/107768.diff


3 Files Affected:

- (modified) clang/docs/ReleaseNotes.rst (+1) 
- (modified) clang/lib/Sema/SemaOverload.cpp (+3) 
- (modified) clang/test/CXX/class.access/p4.cpp (+14-2) 


``````````diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index e44aefa90ab386..0de249ced8309a 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -763,6 +763,7 @@ Bug Fixes to C++ Support
 - Fixed a bug where bounds of partially expanded pack indexing expressions were checked too early. (#GH116105)
 - Fixed an assertion failure caused by using ``consteval`` in condition in consumed analyses. (#GH117385)
 - Fix a crash caused by incorrect argument position in merging deduced template arguments. (#GH113659)
+- Fix a bug where private access specifier of overloaded function not respected. (#GH107629)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 4c9e37bd286dee..35389957adf32d 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -16305,6 +16305,9 @@ ExprResult Sema::FixOverloadedFunctionReference(Expr *E, DeclAccessPair Found,
   }
 
   if (UnresolvedLookupExpr *ULE = dyn_cast<UnresolvedLookupExpr>(E)) {
+    if (Found.getAccess() == AS_none) {
+      CheckUnresolvedLookupAccess(ULE, Found);
+    }
     // FIXME: avoid copy.
     TemplateArgumentListInfo TemplateArgsBuffer, *TemplateArgs = nullptr;
     if (ULE->hasExplicitTemplateArgs()) {
diff --git a/clang/test/CXX/class.access/p4.cpp b/clang/test/CXX/class.access/p4.cpp
index ca98c9f90bd89e..6d4c8c004911db 100644
--- a/clang/test/CXX/class.access/p4.cpp
+++ b/clang/test/CXX/class.access/p4.cpp
@@ -21,11 +21,13 @@ namespace test0 {
   public:
     void foo(Public&);
   protected:
-    void foo(Protected&); // expected-note 2 {{declared protected here}}
+    void foo(Protected&); // expected-note 4 {{declared protected here}}
   private:
-    void foo(Private&); // expected-note 2 {{declared private here}}
+    void foo(Private&); // expected-note 4 {{declared private here}}
   };
 
+  class B : public A {};
+
   void test(A *op) {
     op->foo(PublicInst);
     op->foo(ProtectedInst); // expected-error {{'foo' is a protected member}}
@@ -35,6 +37,16 @@ namespace test0 {
     void (A::*b)(Protected&) = &A::foo; // expected-error {{'foo' is a protected member}}
     void (A::*c)(Private&) = &A::foo; // expected-error {{'foo' is a private member}}
   }
+
+  void test(B *op) {
+    op->foo(PublicInst);
+    op->foo(ProtectedInst); // expected-error {{'foo' is a protected member}}
+    op->foo(PrivateInst); // expected-error {{'foo' is a private member}}
+
+    void (B::*a)(Public&) = &B::foo;
+    void (B::*b)(Protected&) = &B::foo; // expected-error {{'foo' is a protected member}}
+    void (B::*c)(Private&) = &B::foo; // expected-error {{'foo' is a private member}}
+  }
 }
 
 // Member operators.

``````````

</details>


https://github.com/llvm/llvm-project/pull/107768