Protect exceptional paths under libcpp-no-exceptions

These tests are of the form

try {
   action-that-may-throw
   assert(!exceptional-condition)
   assert(some-other-facts)
 } catch (relevant-exception) {
   assert(exceptional-condition)
 }

Under libcpp-no-exceptions there is still value in verifying
some-other-facts while avoiding the exceptional case. So for these tests
just conditionally check some-other-facts if exceptional-condition is
false. When exception are supported make sure that a true
exceptional-condition throws an exception

Differential Revision: https://reviews.llvm.org/D26136



git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@285697 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/strings/basic.string/string.modifiers/string_copy/copy.pass.cpp

@@ -7,7 +7,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: libcpp-no-exceptions
 // <string>
 
 // size_type copy(charT* s, size_type n, size_type pos = 0) const;
@@ -25,20 +24,29 @@ void
 test(S str, typename S::value_type* s, typename S::size_type n,
      typename S::size_type pos)
 {
-    try
+    const S& cs = str;
+    if (pos <= cs.size())
     {
-        const S& cs = str;
         typename S::size_type r = cs.copy(s, n, pos);
-        assert(pos <= cs.size());
         typename S::size_type rlen = std::min(n, cs.size() - pos);
         assert(r == rlen);
         for (r = 0; r < rlen; ++r)
             assert(S::traits_type::eq(cs[pos+r], s[r]));
     }
-    catch (std::out_of_range&)
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    else
     {
-        assert(pos > str.size());
+        try
+        {
+            typename S::size_type r = cs.copy(s, n, pos);
+            assert(false);
+        }
+        catch (std::out_of_range&)
+        {
+            assert(pos > str.size());
+        }
     }
+#endif
 }
 
 int main()