[clang-tidy] bugprone-exception-escape didn't detech catching of an exception with pointer type by void * exception handler (#99773)

As in title, code which checks eligibility of exceptions with pointer
types to be handled by exception handler of type `void *` disallowed
this case. It was working like this:

```c++
if (isStandardPointerConvertible(ExceptionCanTy, HandlerCanTy) &&
          isUnambiguousPublicBaseClass(
              ExceptionCanTy->getTypePtr()->getPointeeType().getTypePtr(),
              HandlerCanTy->getTypePtr()->getPointeeType().getTypePtr())) {
```

but in `isUnambiguousPublicBaseClass` there was code which looked for
definitions:

```c++
bool isUnambiguousPublicBaseClass(const Type *DerivedType,
                                  const Type *BaseType) {
  const auto *DerivedClass =
      DerivedType->getCanonicalTypeUnqualified()->getAsCXXRecordDecl();
  const auto *BaseClass =
      BaseType->getCanonicalTypeUnqualified()->getAsCXXRecordDecl();
  if (!DerivedClass || !BaseClass)
    return false;
```

This code disallowed usage of `void *` type which was already correctly
detected in `isStandardPointerConvertible`.

AFAIK this seems like misinterpretation of specification:

> 14.4 Handling an exception
> a standard [pointer conversion](https://eel.is/c++draft/conv.ptr) not
involving conversions to pointers to private or protected or ambiguous
classes
(https://eel.is/c++draft/except.handle#3.3.1)

and 

> 7.3.12 Pointer conversions
> ... If B is an inaccessible
([[class.access]](https://eel.is/c++draft/class.access)) or ambiguous
([[class.member.lookup]](https://eel.is/c++draft/class.member.lookup))
base class of D, a program that necessitates this conversion is
ill-formed[.](https://eel.is/c++draft/conv.ptr#3.sentence-2) ...
(https://eel.is/c++draft/conv.ptr#3)

14.4 is carving out private, protected, and ambiguous base classes, but
they are already carved out in 7.3.12 and implemented in
`isStandardPointerConvertible`

---------

Co-authored-by: Piotr Zegar <[email protected]>

Author: hanickadot

clang-tools-extra/clang-tidy/utils/ExceptionAnalyzer.cpp

@@ -141,7 +141,10 @@ bool isStandardPointerConvertible(QualType From, QualType To) {
     if (RD->isCompleteDefinition() &&
         isBaseOf(From->getPointeeType().getTypePtr(),
                  To->getPointeeType().getTypePtr())) {
-      return true;
+      // If B is an inaccessible or ambiguous base class of D, a program
+      // that necessitates this conversion is ill-formed
+      return isUnambiguousPublicBaseClass(From->getPointeeType().getTypePtr(),
+                                          To->getPointeeType().getTypePtr());
     }
   }
 
@@ -375,10 +378,7 @@ bool ExceptionAnalyzer::ExceptionInfo::filterByCatch(
         isPointerOrPointerToMember(ExceptionCanTy->getTypePtr())) {
       // A standard pointer conversion not involving conversions to pointers to
       // private or protected or ambiguous classes ...
-      if (isStandardPointerConvertible(ExceptionCanTy, HandlerCanTy) &&
-          isUnambiguousPublicBaseClass(
-              ExceptionCanTy->getTypePtr()->getPointeeType().getTypePtr(),
-              HandlerCanTy->getTypePtr()->getPointeeType().getTypePtr())) {
+      if (isStandardPointerConvertible(ExceptionCanTy, HandlerCanTy)) {
         TypesToDelete.push_back(ExceptionTy);
       }
       // A function pointer conversion ...

clang-tools-extra/docs/ReleaseNotes.rst

@@ -247,6 +247,10 @@ Changes in existing checks
   where source is already a ``void``` pointer, making middle ``void`` pointer
   casts bug-free.
 
+- Improved :doc:`bugprone-exception-escape
+  <clang-tidy/checks/bugprone/exception-escape>`  check to correctly detect exception 
+  handler of type ``CV void *`` as catching all  ``CV`` compatible pointer types.
+
 - Improved :doc:`bugprone-forwarding-reference-overload
   <clang-tidy/checks/bugprone/forwarding-reference-overload>`
   check to ignore deleted constructors which won't hide other overloads.

clang-tools-extra/test/clang-tidy/checkers/bugprone/exception-escape.cpp

@@ -756,3 +756,21 @@ struct test_implicit_throw {
 };
 
 }}
+
+void pointer_exception_can_not_escape_with_const_void_handler() noexcept {
+  // CHECK-MESSAGES-NOT: :[[@LINE-1]]:6: warning: an exception may be thrown in function 'pointer_exception_can_not_escape_with_const_void_handler' which should not throw exceptions
+  const int value = 42;
+  try {
+    throw &value;
+  } catch (const void *) {
+  }
+}
+
+void pointer_exception_can_not_escape_with_void_handler() noexcept {
+  // CHECK-MESSAGES-NOT: :[[@LINE-1]]:6: warning: an exception may be thrown in function 'pointer_exception_can_not_escape_with_void_handler' which should not throw exceptions
+  int value = 42;
+  try {
+    throw &value;
+  } catch (void *) {
+  }
+}