From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Fri, 4 Dec 2015 03:00:44 +0000 (+0000)
Subject: Don't assert if evaluation of an expression that we're syntactically required
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=b659b7b860e586f38438b12eeaa417d41028fe63;p=clang

Don't assert if evaluation of an expression that we're syntactically required
to treat as an ICE results in undefined behavior. Instead, return the "natural"
result of the operation (signed wraparound / inf / nan).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@254699 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index d80f466d99..ffaf742030 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -9408,7 +9408,11 @@ bool Expr::isIntegerConstantExpr(llvm::APSInt &Value, const ASTContext &Ctx,
 
   if (!isIntegerConstantExpr(Ctx, Loc))
     return false;
-  if (!EvaluateAsInt(Value, Ctx))
+  // The only possible side-effects here are due to UB discovered in the
+  // evaluation (for instance, INT_MAX + 1). In such a case, we are still
+  // required to treat the expression as an ICE, so we produce the folded
+  // value.
+  if (!EvaluateAsInt(Value, Ctx, SE_AllowSideEffects))
     llvm_unreachable("ICE cannot be evaluated!");
   return true;
 }
diff --git a/test/SemaCXX/constant-expression.cpp b/test/SemaCXX/constant-expression.cpp
index e01acdd46f..f82a692093 100644
--- a/test/SemaCXX/constant-expression.cpp
+++ b/test/SemaCXX/constant-expression.cpp
@@ -141,3 +141,5 @@ namespace rdar16064952 {
    unsigned w = ({int a = b.val[sizeof(0)]; 0; }); // expected-warning {{use of GNU statement expression extension}}
   }
 }
+
+char PR17381_ice = 1000000 * 1000000; // expected-warning {{overflow}} expected-warning {{changes value}}