Handle tests for noexcept that expect a false value

[rogfer01]

Summary

Under libcpp-no-exceptions, noexcept is trivially true. Some tests expect in the usual setting to return false. Wrap these tests in a convenience macro.

[EricWF]

Have you tested this against GCC which has different noexcept semantics?

If so this LGTM minus possibly addressing the inline comments.

test/libcxx/strings/iterators.exceptions.pass.cpp

55 ↗

(On Diff #79944)

I would prefer something like this if possible:

#ifndef TEST_HAS_NO_EXCEPTIONS
static const bool expect = false;
#else
static const bool expect = true;
#endif
static_assert(std::__libcpp_string_gets_noexcept_iterator<...>::value == expect);

(Also the double negation of TEST_FOR_FALSE(!foo) is weird)

[rogfer01]

• Rewrite the adjusted tests in the way suggested by @EricWF
• Also check that this test works in a GCC-built libcxx

[EricWF]

Please address the inline comments before committing.

test/libcxx/strings/iterators.exceptions.pass.cpp

29 ↗

(On Diff #80235)

We can't use constexpr because these tests run in C++03. However const bool expected = ... should give you a value you can use in constant expressions.

[rogfer01]

test/libcxx/strings/iterators.exceptions.pass.cpp

29 ↗

(On Diff #80235)

Ah, I was confused by the usage of C++11 headers in this file but I will use a static const bool instead. Thanks.

[EricWF]

test/libcxx/strings/iterators.exceptions.pass.cpp

29 ↗

(On Diff #80235)

No worries. It is super confusing, especially since we can use static_assert but not constexpr. Libc++ goes out of its way to provide as much C++11 in C++03 as possible, but there are weird limitations.

[rogfer01]

Do not use constexpr.

libcxx/trunk/test/libcxx/strings/iterators.exceptions.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is dual licensed under the MIT and the University of Illinois Open
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
-// XFAIL: libcpp-no-exceptions
 // <iterator>
 
 // __libcpp_is_trivial_iterator<Tp>
 
 // __libcpp_string_gets_noexcept_iterator determines if an iterator can be used
 // w/o worrying about whether or not certain operations can throw.
 // This gives us a "fast path for string operations"
 //
 
 #include <iterator>
 #include <cassert>
 #include <string>
 #include <vector>
 #include <initializer_list>
 
 #include "test_macros.h"
 #include "test_iterators.h"
 
+#ifndef TEST_HAS_NO_EXCEPTIONS
+static const bool expected = false;
+#else
+// Under libcpp-no-exceptions all noexcept expressions are trivially true, so
+// any check for a noexcept returning false must actually check for it being
+// true.
+static const bool expected = true;
+#endif
+
 int main()
 {
 //  basic tests
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<char *>::value), "");
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<const char *>::value), "");
 
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::move_iterator<char *> >      ::value), "");
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::move_iterator<const char *> >::value), "");
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::reverse_iterator<char *> >      ::value), "");
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::reverse_iterator<const char *> >::value), "");
 
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::__wrap_iter<char *> >      ::value), "");
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::__wrap_iter<const char *> >::value), "");
 
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::reverse_iterator<std::__wrap_iter<char *> > > ::value), "");
 
 //  iterators in the libc++ test suite
-    static_assert((!std::__libcpp_string_gets_noexcept_iterator<output_iterator       <char *> >::value), "");
-    static_assert((!std::__libcpp_string_gets_noexcept_iterator<input_iterator        <char *> >::value), "");
-    static_assert((!std::__libcpp_string_gets_noexcept_iterator<forward_iterator      <char *> >::value), "");
-    static_assert((!std::__libcpp_string_gets_noexcept_iterator<bidirectional_iterator<char *> >::value), "");
-    static_assert((!std::__libcpp_string_gets_noexcept_iterator<random_access_iterator<char *> >::value), "");
-    static_assert((!std::__libcpp_string_gets_noexcept_iterator<ThrowingIterator      <char *> >::value), "");
+    static_assert(std::__libcpp_string_gets_noexcept_iterator<output_iterator       <char *> >::value == expected, "");
+    static_assert(std::__libcpp_string_gets_noexcept_iterator<input_iterator        <char *> >::value == expected, "");
+    static_assert(std::__libcpp_string_gets_noexcept_iterator<forward_iterator      <char *> >::value == expected, "");
+    static_assert(std::__libcpp_string_gets_noexcept_iterator<bidirectional_iterator<char *> >::value == expected, "");
+    static_assert(std::__libcpp_string_gets_noexcept_iterator<random_access_iterator<char *> >::value == expected, "");
+    static_assert(std::__libcpp_string_gets_noexcept_iterator<ThrowingIterator      <char *> >::value == expected, "");
 
 #if TEST_STD_VER >= 11
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<NonThrowingIterator   <char *> >::value), "");
 #else
-    static_assert((!std::__libcpp_string_gets_noexcept_iterator<NonThrowingIterator   <char *> >::value), "");
+    static_assert(std::__libcpp_string_gets_noexcept_iterator<NonThrowingIterator   <char *> >::value == expected, "");
 #endif
 
 //
 //  iterators from libc++'s containers
 //
 
 //  string
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::vector<char>::iterator>              ::value), "");