Add _LIBCPP_DIAGNOSE_WARNING and _LIBCPP_DIAGNOSE_ERROR macros.

Clang recently added a `diagnose_if(cond, msg, type)` attribute
which can be used to generate diagnostics when `cond` is a constant
expression that evaluates to true. Otherwise no attribute has no
effect.

This patch adds _LIBCPP_DIAGNOSE_ERROR/WARNING macros which
use this new attribute. Additionally this patch implements
a diagnostic message when a non-const-callable comparator is
given to a container.

Note: For now the warning version of the diagnostic is useless
within libc++ since warning diagnostics are suppressed by the
system header pragma. I'm going to work on fixing this.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@291961 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/compiler.py

@@ -296,7 +296,7 @@ class CXXCompiler(object):
 
     def addWarningFlagIfSupported(self, flag):
         if self.hasWarningFlag(flag):
-            assert flag not in self.warning_flags
-            self.warning_flags += [flag]
+            if flag not in self.warning_flags:
+                self.warning_flags += [flag]
             return True
         return False

test/libcxx/containers/associative/non_const_comparator.fail.cpp

@@ -0,0 +1,45 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+// REQUIRES: diagnose-if-support, verify-support
+
+// Test that libc++ generates a warning diagnostic when the container is
+// provided a non-const callable comparator.
+
+#include <set>
+#include <map>
+
+struct BadCompare {
+  template <class T, class U>
+  bool operator()(T const& t, U const& u) {
+    return t < u;
+  }
+};
+
+int main() {
+  static_assert(!std::__is_const_comparable<BadCompare, int>::value, "");
+  // expected-warning@__tree:* 4 {{the specified comparator type does not provide a const call operator}}
+  {
+    using C = std::set<int, BadCompare>;
+    C s;
+  }
+  {
+    using C = std::multiset<long, BadCompare>;
+    C s;
+  }
+  {
+    using C = std::map<int, int, BadCompare>;
+    C s;
+  }
+  {
+    using C = std::multimap<long, int, BadCompare>;
+    C s;
+  }
+}

test/libcxx/test/config.py

@@ -712,33 +712,35 @@ class Configuration(object):
                 ['c++11', 'c++14', 'c++1z'])) != 0
         enable_warnings = self.get_lit_bool('enable_warnings',
                                             default_enable_warnings)
-        if enable_warnings:
-            self.cxx.useWarnings(True)
-            self.cxx.warning_flags += [
-                '-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER',
-                '-Wall', '-Wextra', '-Werror'
-            ]
-            self.cxx.addWarningFlagIfSupported('-Wshadow')
-            self.cxx.addWarningFlagIfSupported('-Wno-unused-command-line-argument')
-            self.cxx.addWarningFlagIfSupported('-Wno-attributes')
-            self.cxx.addWarningFlagIfSupported('-Wno-pessimizing-move')
-            self.cxx.addWarningFlagIfSupported('-Wno-c++11-extensions')
-            self.cxx.addWarningFlagIfSupported('-Wno-user-defined-literals')
-            # These warnings should be enabled in order to support the MSVC
-            # team using the test suite; They enable the warnings below and
-            # expect the test suite to be clean.
-            self.cxx.addWarningFlagIfSupported('-Wsign-compare')
-            self.cxx.addWarningFlagIfSupported('-Wunused-variable')
-            self.cxx.addWarningFlagIfSupported('-Wunused-parameter')
-            self.cxx.addWarningFlagIfSupported('-Wunreachable-code')
-            # FIXME: Enable the two warnings below.
-            self.cxx.addWarningFlagIfSupported('-Wno-conversion')
+        self.cxx.useWarnings(enable_warnings)
+        self.cxx.warning_flags += [
+            '-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER',
+            '-Wall', '-Wextra', '-Werror'
+        ]
+        if self.cxx.hasWarningFlag('-Wuser-defined-warnings'):
+            self.cxx.warning_flags += ['-Wuser-defined-warnings']
+            self.config.available_features.add('diagnose-if-support')
+        self.cxx.addWarningFlagIfSupported('-Wshadow')
+        self.cxx.addWarningFlagIfSupported('-Wno-unused-command-line-argument')
+        self.cxx.addWarningFlagIfSupported('-Wno-attributes')
+        self.cxx.addWarningFlagIfSupported('-Wno-pessimizing-move')
+        self.cxx.addWarningFlagIfSupported('-Wno-c++11-extensions')
+        self.cxx.addWarningFlagIfSupported('-Wno-user-defined-literals')
+        # These warnings should be enabled in order to support the MSVC
+        # team using the test suite; They enable the warnings below and
+        # expect the test suite to be clean.
+        self.cxx.addWarningFlagIfSupported('-Wsign-compare')
+        self.cxx.addWarningFlagIfSupported('-Wunused-variable')
+        self.cxx.addWarningFlagIfSupported('-Wunused-parameter')
+        self.cxx.addWarningFlagIfSupported('-Wunreachable-code')
+        # FIXME: Enable the two warnings below.
+        self.cxx.addWarningFlagIfSupported('-Wno-conversion')
+        self.cxx.addWarningFlagIfSupported('-Wno-unused-local-typedef')
+        std = self.get_lit_conf('std', None)
+        if std in ['c++98', 'c++03']:
+            # The '#define static_assert' provided by libc++ in C++03 mode
+            # causes an unused local typedef whenever it is used.
             self.cxx.addWarningFlagIfSupported('-Wno-unused-local-typedef')
-            std = self.get_lit_conf('std', None)
-            if std in ['c++98', 'c++03']:
-                # The '#define static_assert' provided by libc++ in C++03 mode
-                # causes an unused local typedef whenever it is used.
-                self.cxx.addWarningFlagIfSupported('-Wno-unused-local-typedef')
 
     def configure_sanitizer(self):
         san = self.get_lit_conf('use_sanitizer', '').strip()

test/libcxx/test/format.py

@@ -223,6 +223,10 @@ class LibcxxTestFormat(object):
             test_cxx.flags += ['-fsyntax-only']
         if use_verify:
             test_cxx.useVerify()
+            test_cxx.useWarnings()
+            if '-Wuser-defined-warnings' in test_cxx.warning_flags:
+                test_cxx.warning_flags += ['-Wno-error=user-defined-warnings']
+
         cmd, out, err, rc = test_cxx.compile(source_path, out=os.devnull)
         expected_rc = 0 if use_verify else 1
         if rc == expected_rc:

test/libcxx/utilities/tuple/tuple.tuple/diagnose_reference_binding.fail.cpp

@@ -30,4 +30,11 @@ int main() {
     // bind rvalue to constructed non-rvalue
     std::tuple<std::string &&> t2("hello"); // expected-note {{requested here}}
     std::tuple<std::string &&> t3(std::allocator_arg, alloc, "hello"); // expected-note {{requested here}}
+
+    // FIXME: The below warnings may get emitted as an error, a warning, or not emitted at all
+    // depending on the flags used to compile this test.
+  {
+    // expected-warning@tuple:* 0+ {{binding reference member 'value' to a temporary value}}
+    // expected-error@tuple:* 0+ {{binding reference member 'value' to a temporary value}}
+  }
 }