Fix PR30520: Fix incomplete type crash when dealing with transparent_union attribute

[arphaman]

Summary

This patch fixes a crash that happens when clang is analyzing a transparent_union attribute on a union which has a field with incomplete type.

(Right now there's also a C++ crash like this when a field has a dependent type, but I plan on fixing it in a separate patch by analyzing the dependent attribute when the dependent union is instantiated).

[rnk]

lgtm, thanks!

[aaron.ballman]

LGTM, thank you!

cfe/trunk/lib/Sema/SemaDeclAttr.cpp

static void handleTransparentUnionAttr(Sema &S, Decl *D,
   QualType FirstType = FirstField->getType();
   if (FirstType->hasFloatingRepresentation() || FirstType->isVectorType()) {
     S.Diag(FirstField->getLocation(),
            diag::warn_transparent_union_attribute_floating)
       << FirstType->isVectorType() << FirstType;
     return;
   }
 
+  if (FirstType->isIncompleteType())
+    return;
   uint64_t FirstSize = S.Context.getTypeSize(FirstType);
   uint64_t FirstAlign = S.Context.getTypeAlign(FirstType);
   for (; Field != FieldEnd; ++Field) {
     QualType FieldType = Field->getType();
+    if (FieldType->isIncompleteType())
+      return;
     // FIXME: this isn't fully correct; we also need to test whether the
     // members of the union would all have the same calling convention as the
     // first member of the union. Checking just the size and alignment isn't
     // sufficient (consider structs passed on the stack instead of in registers
     // as an example).
     if (S.Context.getTypeSize(FieldType) != FirstSize ||
         S.Context.getTypeAlign(FieldType) > FirstAlign) {
       // Warn if we drop the attribute.

cfe/trunk/test/Sema/transparent-union.c

union pr15134v2 {
   struct { // expected-note {{alignment of first field is 32 bits}}
     unsigned int u1;
     unsigned int u2;
   };
   struct {  // expected-warning {{alignment of field '' (64 bits) does not match the alignment of the first field in transparent union; transparent_union attribute ignored}}
     unsigned int u3;
   } __attribute__((aligned(8)));
 } __attribute__((transparent_union));
+
+union pr30520v { void b; } __attribute__((transparent_union)); // expected-error {{field has incomplete type 'void'}}
+
+union pr30520a { int b[]; } __attribute__((transparent_union)); // expected-error {{field has incomplete type 'int []'}}
+
+// expected-note@+1 2 {{forward declaration of 'struct stb'}}
+union pr30520s { struct stb b; } __attribute__((transparent_union)); // expected-error {{field has incomplete type 'struct stb'}}
+
+union pr30520s2 { int *v; struct stb b; } __attribute__((transparent_union)); // expected-error {{field has incomplete type 'struct stb'}}