Fix noderef for AddrOf on MemberExpr

[thejh]

Summary

As part of this change, one existing test case has to be adjusted
because it accidentally stripped the NoDeref attribute without
getting caught.

Depends on D92140

[thejh]

(I marked this as depending on D92140 because if you apply this patch to the current HEAD directly, the tests will break.)

[leonardchan]

LGTM. Thanks

clang/test/Frontend/noderef.c

75–76

These two can probably be removed since we have

p = &s->a;
p = &(*s).b;

above.

[thejh]

Removed duplicate tests as suggested by leonardchan

[thejh]

clang/test/Frontend/noderef.c

75–76

Good point, I've removed them now.

[leonardchan]

Ok this time I remembered the email. Unsure why the bug isn't automatically closed though.

clang/lib/Sema/SemaExprMember.cpp

if (const ReferenceType *Ref = MemberType->getAs<ReferenceType>()) {
     Qualifiers MemberQuals =
         Context.getCanonicalType(MemberType).getQualifiers();
 
     assert(!MemberQuals.hasAddressSpace());
 
     Qualifiers Combined = BaseQuals + MemberQuals;
     if (Combined != MemberQuals)
       MemberType = Context.getQualifiedType(MemberType, Combined);
+
+    // Pick up NoDeref from the base in case we end up using AddrOf on the
+    // result. E.g. the expression
+    //     &someNoDerefPtr->pointerMember
+    // should be a noderef pointer again.
+    if (BaseType->hasAttr(attr::NoDeref))
+      MemberType =
+          Context.getAttributedType(attr::NoDeref, MemberType, MemberType);
   }
 
   auto *CurMethod = dyn_cast<CXXMethodDecl>(CurContext);
   if (!(CurMethod && CurMethod->isDefaulted()))
     UnusedPrivateFields.remove(Field);
 
   ExprResult Base = PerformObjectMemberConversion(BaseExpr, SS.getScopeRep(),
                                                   FoundDecl, Field);

clang/test/Frontend/noderef.c

int test() {
 
   // Most things in sizeof() can't actually access memory
   x = sizeof(s->a);          // ok
   x = sizeof(*s);            // ok
   x = sizeof(s[0]);          // ok
   x = sizeof(s->a + (s->b)); // ok
   x = sizeof(int[++s->a]);   // expected-warning{{dereferencing s; was declared with a 'noderef' type}}
 
+  // Struct member access should carry NoDeref type information through to an
+  // enclosing AddrOf.
+  p = &s->a;    // ok
+  p = &(*s).a;  // ok
+  p2 = &s->a;   // expected-warning{{casting to dereferenceable pointer removes 'noderef' attribute}}
+  p2 = &(*s).a; // expected-warning{{casting to dereferenceable pointer removes 'noderef' attribute}}
+  x = *&s->a;   // expected-warning{{dereferencing expression marked as 'noderef'}}
+
   // Nested struct access
   struct S2 NODEREF *s2_noderef;    // expected-note 5 {{s2_noderef declared here}}
   p = s2_noderef->a;  // ok since result is an array in a struct
   p = (*s2_noderef).a; // ok since result is an array in a struct
   p = s2_noderef->a2; // ok
   p = s2_noderef->b;  // expected-warning{{dereferencing s2_noderef; was declared with a 'noderef' type}}
   p = s2_noderef->b2; // expected-warning{{dereferencing s2_noderef; was declared with a 'noderef' type}}
   s = s2_noderef->s;  // expected-warning{{dereferencing s2_noderef; was declared with a 'noderef' type}}
int test() {
   elem = *arr3;
 
   // Combinations between indirection, subscript, and member access
   struct S2 NODEREF *s2_arr[10];
   struct S2 NODEREF *s2_arr2[10][10];
 
   p = s2_arr[1]->a;
   p = s2_arr[1]->b; // expected-warning{{dereferencing expression marked as 'noderef'}}
-  int **bptr = &s2_arr[1]->b;
+  int *NODEREF *bptr = &s2_arr[1]->b;
 
   x = s2->s2->a;        // expected-warning{{dereferencing expression marked as 'noderef'}}
   x = s2_noderef->a[1]; // expected-warning{{dereferencing s2_noderef; was declared with a 'noderef' type}}
   p = &s2_noderef->a[1];
 
   // Casting to dereferenceable pointer
   p2 = p;             // expected-warning{{casting to dereferenceable pointer removes 'noderef' attribute}}
   p2 = *q;            // expected-warning{{casting to dereferenceable pointer removes 'noderef' attribute}}