[Bounds-Safety] restrict sized_by for types w/o size unless incomplete

Emit an error when sized_by or sized_by_or_null is used on sizeless
types, function pointers and pointers to structs with flexible array
members. Although we *could* track their size, it is not useful and
indexing would not work.

Author: hnrklssn

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -6588,7 +6588,7 @@ def err_count_attr_refer_to_union : Error<
 def note_flexible_array_counted_by_attr_field : Note<
   "field %0 declared here">;
 def err_counted_by_attr_pointee_unknown_size : Error<
-  "'%select{counted_by|counted_by_or_null}4' %select{cannot|should not}3 be applied to %select{"
+  "'%select{counted_by|sized_by|counted_by_or_null|sized_by_or_null}4' %select{cannot|should not}3 be applied to %select{"
     "a pointer with pointee|" // pointer
     "an array with element}0" // array
   " of unknown size because %1 is %select{"

clang/lib/Sema/SemaDeclAttr.cpp

@@ -5941,7 +5941,7 @@ CheckCountedByAttrOnField(Sema &S, FieldDecl *FD, Expr *E,
   // only `PointeeTy->isStructureTypeWithFlexibleArrayMember()` is reachable
   // when `FieldTy->isArrayType()`.
   bool ShouldWarn = false;
-  if (PointeeTy->isIncompleteType()) {
+  if (PointeeTy->isIncompleteType() && !CountInBytes) {
     InvalidTypeKind = CountedByInvalidPointeeTypeKind::INCOMPLETE;
   } else if (PointeeTy->isSizelessType()) {
     InvalidTypeKind = CountedByInvalidPointeeTypeKind::SIZELESS;
@@ -5960,14 +5960,13 @@ CheckCountedByAttrOnField(Sema &S, FieldDecl *FD, Expr *E,
     InvalidTypeKind = CountedByInvalidPointeeTypeKind::FLEXIBLE_ARRAY_MEMBER;
   }
 
-  if (InvalidTypeKind != CountedByInvalidPointeeTypeKind::VALID &&
-      !CountInBytes) {
+  if (InvalidTypeKind != CountedByInvalidPointeeTypeKind::VALID) {
     unsigned DiagID = ShouldWarn
                           ? diag::warn_counted_by_attr_elt_type_unknown_size
                           : diag::err_counted_by_attr_pointee_unknown_size;
     S.Diag(FD->getBeginLoc(), DiagID)
         << SelectPtrOrArr << PointeeTy << (int)InvalidTypeKind
-        << (ShouldWarn ? 1 : 0) << OrNull << FD->getSourceRange();
+        << (ShouldWarn ? 1 : 0) << Kind << FD->getSourceRange();
     return true;
   }
 

clang/test/Sema/attr-sized-by-last-field.c

@@ -137,5 +137,6 @@ struct on_member_ptr_fn_ptr_ty {
 
 struct on_member_ptr_fn_ty {
   int size;
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'fn_ty' (aka 'void (int)') is a function type}}
   fn_ty * ptr __sized_by(size);
 };

clang/test/Sema/attr-sized-by-late-parsed-struct-ptrs.c

@@ -48,12 +48,14 @@ struct on_member_pointer_fn_ptr_ty_ptr_ty {
 
 struct on_member_pointer_fn_ty {
   // buffer of function(s) with size `size` is allowed
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   void (*fn_ptr)(void) __sized_by(size);
   int size;
 };
 
 struct on_member_pointer_fn_ptr_ty_ty {
   // buffer of function(s) with size `size` is allowed
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   fn_ptr_ty fn_ptr __sized_by(size);
   int size;
 };
@@ -64,6 +66,7 @@ struct has_unannotated_vla {
 };
 
 struct on_member_pointer_struct_with_vla {
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'struct has_unannotated_vla' is a struct type with a flexible array member}}
   struct has_unannotated_vla* objects __sized_by(size);
   int size;
 };
@@ -75,6 +78,7 @@ struct has_annotated_vla {
 };
 
 struct on_member_pointer_struct_with_annotated_vla {
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'struct has_annotated_vla' is a struct type with a flexible array member}}
   struct has_annotated_vla* objects __sized_by(size);
   int size;
 };

clang/test/Sema/attr-sized-by-or-null-last-field.c

@@ -137,5 +137,6 @@ struct on_member_ptr_fn_ptr_ty {
 
 struct on_member_ptr_fn_ty {
   int size;
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'fn_ty' (aka 'void (int)') is a function type}}
   fn_ty * ptr __sized_by_or_null(size);
 };

clang/test/Sema/attr-sized-by-or-null-late-parsed-struct-ptrs.c

@@ -48,12 +48,14 @@ struct on_member_pointer_fn_ptr_ty_ptr_ty {
 
 struct on_member_pointer_fn_ty {
   // buffer of function(s) with size `size` is allowed
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   void (*fn_ptr)(void) __sized_by_or_null(size);
   int size;
 };
 
 struct on_member_pointer_fn_ptr_ty_ty {
   // buffer of function(s) with size `size` is allowed
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   fn_ptr_ty fn_ptr __sized_by_or_null(size);
   int size;
 };
@@ -64,6 +66,7 @@ struct has_unannotated_vla {
 };
 
 struct on_member_pointer_struct_with_vla {
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'struct has_unannotated_vla' is a struct type with a flexible array member}}
   struct has_unannotated_vla* objects __sized_by_or_null(size);
   int size;
 };
@@ -75,6 +78,7 @@ struct has_annotated_vla {
 };
 
 struct on_member_pointer_struct_with_annotated_vla {
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'struct has_annotated_vla' is a struct type with a flexible array member}}
   struct has_annotated_vla* objects __sized_by_or_null(size);
   int size;
 };

clang/test/Sema/attr-sized-by-or-null-struct-ptrs-sizeless-types.c

@@ -5,6 +5,7 @@
 
 struct on_sizeless_pointee_ty {
     int size;
+    // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because '__SVInt8_t' is a sizeless type}}
     __SVInt8_t* member __sized_by_or_null(size);
 };
 

clang/test/Sema/attr-sized-by-or-null-struct-ptrs.c

@@ -49,12 +49,14 @@ struct on_member_pointer_fn_ptr_ty_ptr_ty {
 struct on_member_pointer_fn_ty {
   int size;
   // buffer of functions with size `size` is allowed
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   void (*fn_ptr)(void) __sized_by_or_null(size);
 };
 
 struct on_member_pointer_fn_ptr_ty_ty {
   int size;
   // buffer of functions with size `size` is allowed
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   fn_ptr_ty fn_ptr __sized_by_or_null(size);
 };
 
@@ -66,6 +68,7 @@ struct has_unannotated_vla {
 struct on_member_pointer_struct_with_vla {
   int size;
   // we know the size so this is fine for tracking size, however indexing would be an issue
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'struct has_unannotated_vla' is a struct type with a flexible array member}}
   struct has_unannotated_vla* objects __sized_by_or_null(size);
 };
 
@@ -77,6 +80,7 @@ struct has_annotated_vla {
 struct on_member_pointer_struct_with_annotated_vla {
   int size;
   // we know the size so this is fine for tracking size, however indexing would be an issue
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'struct has_annotated_vla' is a struct type with a flexible array member}}
   struct has_annotated_vla* objects __sized_by_or_null(size);
 };
 
@@ -136,11 +140,13 @@ struct on_member_pointer_fn_ptr_ty_ptr_ty_pos {
 
 struct on_member_pointer_fn_ty_ty_pos {
   int size;
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   void (* __sized_by_or_null(size) fn_ptr)(void);
 };
 
 struct on_member_pointer_fn_ptr_ty_ty_pos {
   int size;
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   fn_ptr_ty __sized_by_or_null(size) fn_ptr;
 };
 
@@ -153,11 +159,13 @@ struct on_member_pointer_fn_ptr_ty_ty_pos_inner {
 
 struct on_member_pointer_struct_with_vla_ty_pos {
   int size;
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'struct has_unannotated_vla' is a struct type with a flexible array member}}
   struct has_unannotated_vla *__sized_by_or_null(size) objects;
 };
 
 struct on_member_pointer_struct_with_annotated_vla_ty_pos {
   int size;
+  // expected-error@+1{{'sized_by_or_null' cannot be applied to a pointer with pointee of unknown size because 'struct has_annotated_vla' is a struct type with a flexible array member}}
   struct has_annotated_vla* __sized_by_or_null(size) objects;
 };
 

clang/test/Sema/attr-sized-by-struct-ptrs-sizeless-types.c

@@ -5,6 +5,7 @@
 
 struct on_sizeless_pointee_ty {
     int count;
+    // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because '__SVInt8_t' is a sizeless type}}
     __SVInt8_t* member __sized_by(count);
 };
 

clang/test/Sema/attr-sized-by-struct-ptrs.c

@@ -49,12 +49,14 @@ struct on_member_pointer_fn_ptr_ty_ptr_ty {
 struct on_member_pointer_fn_ty {
   int size;
   // buffer of functions with size `size` is allowed
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   void (*fn_ptr)(void) __sized_by(size);
 };
 
 struct on_member_pointer_fn_ptr_ty_ty {
   int size;
   // buffer of functions with size `size` is allowed
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   fn_ptr_ty fn_ptr __sized_by(size);
 };
 
@@ -66,6 +68,7 @@ struct has_unannotated_vla {
 struct on_member_pointer_struct_with_vla {
   int size;
   // we know the size so this is fine for tracking size, however indexing would be an issue
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'struct has_unannotated_vla' is a struct type with a flexible array member}}
   struct has_unannotated_vla* objects __sized_by(size);
 };
 
@@ -77,6 +80,7 @@ struct has_annotated_vla {
 struct on_member_pointer_struct_with_annotated_vla {
   int size;
   // we know the size so this is fine for tracking size, however indexing would be an issue
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'struct has_annotated_vla' is a struct type with a flexible array member}}
   struct has_annotated_vla* objects __sized_by(size);
 };
 
@@ -136,11 +140,13 @@ struct on_member_pointer_fn_ptr_ty_ptr_ty_pos {
 
 struct on_member_pointer_fn_ty_ty_pos {
   int size;
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   void (* __sized_by(size) fn_ptr)(void);
 };
 
 struct on_member_pointer_fn_ptr_ty_ty_pos {
   int size;
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'void (void)' is a function type}}
   fn_ptr_ty __sized_by(size) fn_ptr;
 };
 
@@ -153,11 +159,13 @@ struct on_member_pointer_fn_ptr_ty_ty_pos_inner {
 
 struct on_member_pointer_struct_with_vla_ty_pos {
   int size;
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'struct has_unannotated_vla' is a struct type with a flexible array member}}
   struct has_unannotated_vla *__sized_by(size) objects;
 };
 
 struct on_member_pointer_struct_with_annotated_vla_ty_pos {
   int size;
+  // expected-error@+1{{'sized_by' cannot be applied to a pointer with pointee of unknown size because 'struct has_annotated_vla' is a struct type with a flexible array member}}
   struct has_annotated_vla* __sized_by(size) objects;
 };