fixup: more restrictions on the pointer type

Disallow function pointers.
Add tests to verify that member/data member pointers also fail.

Author: a-nogikh

clang/lib/Sema/SemaDeclAttr.cpp

@@ -1857,11 +1857,15 @@ static bool checkSpanLikeType(const QualType &Ty) {
     return false;
   const QualType FirstFieldType = FieldsBegin->getType();
   const QualType SecondFieldType = std::next(FieldsBegin)->getType();
+  auto validatePointerType = [](const QualType &T) {
+    // It must not point to functions.
+    return T->isPointerType() && !T->isFunctionPointerType();
+  };
   // Verify two possible orderings.
-  return (FirstFieldType->isAnyPointerType() &&
+  return (validatePointerType(FirstFieldType) &&
           SecondFieldType->isIntegerType()) ||
          (FirstFieldType->isIntegerType() &&
-          SecondFieldType->isAnyPointerType());
+          validatePointerType(SecondFieldType));
 }
 
 static void handleMallocSpanAttr(Sema &S, Decl *D, const ParsedAttr &AL) {

clang/test/Sema/attr-malloc_span.c

@@ -29,3 +29,10 @@ typedef struct {
   size_t n2;
 } invalid_span2;
 invalid_span2  returns_non_std_span2  (void) __attribute((malloc_span)); // expected-warning {{attribute only applies to functions that return span-like structures}}
+
+// Function pointers are not allowed.
+typedef struct {
+  int (*func_ptr)(void);
+  size_t n;
+} func_span;
+func_span  returns_func_span  (void) __attribute((malloc_span)); // expected-warning {{attribute only applies to functions that return span-like structures}}

clang/test/SemaCXX/attr-malloc_span.cpp

@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify %s
+
+class SomeClass {
+public:
+  int Data;
+};
+
+// Returning pointers to data members is not allowed.
+struct DataMemberSpan {
+  int SomeClass::* member_ptr;
+  int n;
+};
+
+DataMemberSpan returns_data_member_span(void) __attribute((malloc_span)) { // expected-warning {{attribute only applies to functions that return span-like structures}}
+  return DataMemberSpan{};
+}
+
+// Returning pointers to member functions is not allowed.
+struct MemberFuncSpan {
+  void (SomeClass::*member_func_ptr)();
+  int n;
+};
+
+MemberFuncSpan returns_member_func_span(void) __attribute((malloc_span)) { // expected-warning {{attribute only applies to functions that return span-like structures}}
+  return MemberFuncSpan{};
+}
+