A call to strlen is not a constant expression, even if we're treating it as a

builtin.

llvm-svn: 148374

clang/lib/AST/ExprConstant.cpp

@@ -3891,8 +3891,15 @@ bool IntExprEvaluator::VisitCallExpr(const CallExpr *E) {
 
   case Builtin::BI__builtin_expect:
     return Visit(E->getArg(0));
-      
+
   case Builtin::BIstrlen:
+    // A call to strlen is not a constant expression.
+    if (Info.getLangOpts().CPlusPlus0x)
+      Info.CCEDiag(E->getExprLoc(), diag::note_constexpr_invalid_function)
+        << /*isConstexpr*/0 << /*isConstructor*/0 << "'strlen'";
+    else
+      Info.CCEDiag(E->getExprLoc(), diag::note_invalid_subexpr_in_const_expr);
+    // Fall through.
   case Builtin::BI__builtin_strlen:
     // As an extension, we support strlen() and __builtin_strlen() as constant
     // expressions when the argument is a string literal.

clang/test/SemaCXX/constexpr-strlen.cpp

@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 %s -std=c++11 -fsyntax-only -verify -pedantic
+
+# 1 "/usr/include/string.h" 1 3 4
+extern "C" {
+  typedef decltype(sizeof(int)) size_t;
+  extern size_t strlen(const char *p);
+}
+
+# 10 "SemaCXX/constexpr-strlen.cpp" 2
+constexpr int n = __builtin_strlen("hello"); // ok
+constexpr int m = strlen("hello"); // expected-error {{constant expression}} expected-note {{non-constexpr function 'strlen' cannot be used in a constant expression}}
+
+// Make sure we can evaluate a call to strlen.
+int arr[3]; // expected-note {{here}}
+int k = arr[strlen("hello")]; // expected-warning {{array index 5}}