[Clang] Fix crash when checking misaligned member with dependent type

[junaire]

Summary

If the type is dependent, we should just discard it and not checking its
alignment as it doesn't exisit yet.
Fixes https://github.com/llvm/llvm-project/issues/58370

[aaron.ballman]

clang/lib/Sema/SemaChecking.cpp

17397

We don't typically use top-level const qualification.

17398–17399

Hmm, is this logic correct? Don't we want:

T->isDependentType() ||
  (T->isPointerType() &&
    (T->getPointeeType()->isIncompleteType() || Context.getTypeAlignInChars(T->getPointeeType()) <= MA->Alignment))

[junaire]

Address Aaron's comments, thanks!

[shafik]

clang/lib/Sema/SemaChecking.cpp

17398–17399

Why did you drop the T->isIntegerType()?

clang/test/SemaCXX/misaligned-member-with-depdent-type.cpp

5

I think since the bug report had malformed code, it would be worth it to include that case as well.

[aaron.ballman]

clang/lib/Sema/SemaChecking.cpp

17398–17399

Whoops! That's totally a typo on my part, I didn't intend to drop it.

[junaire]

Add the original mailformed test case, thanks Shafik!

[junaire]

clang/lib/Sema/SemaChecking.cpp

17398–17399

Why did you drop the T->isIntegerType()?

There may be some misunderstanding here. So previously I hoist the pointer-related checks and put T->isDependentType() into it. After Aaron's words, I realized it was wrong so I changed the whole check condition to is T an integer type? || is T a dependent type ?|| is T a pointer type and other constraints (put them on the same level)

That said you're looking at the old diff so there's nothing need to worried about :)

[aaron.ballman]

LGTM!

clang/lib/Sema/SemaChecking.cpp

for (MisalignedMember &m : MisalignedMembers) {
     Diag(m.E->getBeginLoc(), diag::warn_taking_address_of_packed_member)
         << m.MD << ND << m.E->getSourceRange();
   }
   MisalignedMembers.clear();
 }
 
 void Sema::DiscardMisalignedMemberAddress(const Type *T, Expr *E) {
   E = E->IgnoreParens();
-  if (!T->isPointerType() && !T->isIntegerType())
+  if (!T->isPointerType() && !T->isIntegerType() && !T->isDependentType())
     return;
   if (isa<UnaryOperator>(E) &&
       cast<UnaryOperator>(E)->getOpcode() == UO_AddrOf) {
     auto *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
     if (isa<MemberExpr>(Op)) {
-      auto MA = llvm::find(MisalignedMembers, MisalignedMember(Op));
+      auto *MA = llvm::find(MisalignedMembers, MisalignedMember(Op));
       if (MA != MisalignedMembers.end() &&
-          (T->isIntegerType() ||
+          (T->isDependentType() || T->isIntegerType() ||
            (T->isPointerType() && (T->getPointeeType()->isIncompleteType() ||
                                    Context.getTypeAlignInChars(
                                        T->getPointeeType()) <= MA->Alignment))))
         MisalignedMembers.erase(MA);
     }
   }
 }
 
 void Sema::RefersToMemberWithReducedAlignment(

clang/test/SemaCXX/misaligned-member-with-depdent-type.cpp

+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct __attribute__((packed)) {
+  unsigned options;
+  template <typename T>
+  void getOptions() {
+      (T *)&options;
+  }
+  template <typename U>
+  void getOptions2() {
+      (U)&options;
+  }
+} s;
+
+struct __attribute__((packed)) { // expected-error {{anonymous structs and classes must be class members}}
+           unsigned options ;
+  template <typename T> getOptions() // expected-error {{a type specifier is required for all declarations}}
+    {
+      (T *) & options;
+    }
+};