Fix a case where Expr::isConstantInitializer would return true for an expression we can't support. In a slightly amusing twist, the case in question was already in the clang regression tests marked as a valid construct. <rdar://problem/10020074>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@147026 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 24 insertions, 10 deletions

diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 40da32284d..9f87161290 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -2550,17 +2550,30 @@ bool Expr::isConstantInitializer(ASTContext &Ctx, bool IsForRef) const {
     if (getType()->isVectorType() && CE->getCastKind() == CK_BitCast)
       return CE->getSubExpr()->isConstantInitializer(Ctx, false);
 
-    // Handle casts with a destination that's a struct or union; this
-    // deals with both the gcc no-op struct cast extension and the
-    // cast-to-union extension.
-    if (getType()->isRecordType())
+    // Handle misc casts we want to ignore.
+    // FIXME: Is it really safe to ignore all these?
+    if (CE->getCastKind() == CK_NoOp ||
+        CE->getCastKind() == CK_LValueToRValue ||
+        CE->getCastKind() == CK_ToUnion ||
+        CE->getCastKind() == CK_ConstructorConversion)
       return CE->getSubExpr()->isConstantInitializer(Ctx, false);
 
-    // Integer->integer casts can be handled here, which is important for
-    // things like (int)(&&x-&&y).  Scary but true.
-    if (getType()->isIntegerType() &&
-        CE->getSubExpr()->getType()->isIntegerType())
-      return CE->getSubExpr()->isConstantInitializer(Ctx, false);
+    // Handle things like (int)(&&x-&&y). It's a bit nasty, but we support it.
+    if (CE->getCastKind() == CK_IntegralCast) {
+      const Expr *E = CE->getSubExpr()->IgnoreParenNoopCasts(Ctx);
+      while (const CastExpr *InnerCE = dyn_cast<CastExpr>(E)) {
+        if (InnerCE->getCastKind() != CK_IntegralCast)
+          break;
+        E = InnerCE->getSubExpr()->IgnoreParenNoopCasts(Ctx);
+      }
+
+      if (const BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
+        if (BO->getOpcode() == BO_Sub &&
+            isa<AddrLabelExpr>(BO->getLHS()->IgnoreParenNoopCasts(Ctx)) &&
+            isa<AddrLabelExpr>(BO->getRHS()->IgnoreParenNoopCasts(Ctx)))
+          return true;
+      }
+    }
 
     break;
   }
diff --git a/test/Sema/static-init.c b/test/Sema/static-init.c
index b4de92713b..ec6d1e8fc0 100644
--- a/test/Sema/static-init.c
+++ b/test/Sema/static-init.c
@@ -19,5 +19,6 @@ struct foo {
 };
 
 union bar u[1];
-struct foo x = {(intptr_t) u}; // no-error
+struct foo x = {(intptr_t) u}; // expected-error {{initializer element is not a compile-time constant}}
 struct foo y = {(char) u}; // expected-error {{initializer element is not a compile-time constant}}
+intptr_t z = (intptr_t) u; // no-error