Enable and fix warnings during the build.

Although CMake adds warning flags, they are ignored in the libc++ headers
because the headers '#pragma system header' themselves.

This patch disables the system header pragma when building libc++ and fixes
the warnings that arose.

The warnings fixed were:
1. <memory> - anonymous structs are a GNU extension
2. <functional> - anonymous structs are a GNU extension.
3. <__hash_table> - Embedded preprocessor directives have undefined behavior.
4. <string> - Definition is missing noexcept from declaration.
5. <__std_stream> - Unused variable.

llvm-svn: 242623

libcxx/CMakeLists.txt

@@ -175,6 +175,8 @@ macro(append_if list condition var)
 endmacro()
 
 # Get warning flags
+# Disable the system header pragma.
+add_definitions(-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 if (NOT MSVC)
   append_if(LIBCXX_COMPILE_FLAGS LIBCXX_HAS_WALL_FLAG -Wall)
   list(APPEND LIBCXX_COMPILE_FLAGS -Werror=return-type)

libcxx/include/__hash_table

@@ -984,15 +984,17 @@ public:
         __equal_range_multi(const _Key& __k) const;
 
     void swap(__hash_table& __u)
+#if _LIBCPP_STD_VER <= 11
         _NOEXCEPT_(
             __is_nothrow_swappable<hasher>::value && __is_nothrow_swappable<key_equal>::value
-#if _LIBCPP_STD_VER <= 11
             && (!allocator_traits<__pointer_allocator>::propagate_on_container_swap::value
                   || __is_nothrow_swappable<__pointer_allocator>::value)
             && (!__node_traits::propagate_on_container_swap::value
                   || __is_nothrow_swappable<__node_allocator>::value)
-#endif
             );
+#else
+     _NOEXCEPT_(__is_nothrow_swappable<hasher>::value && __is_nothrow_swappable<key_equal>::value);
+#endif
 
     _LIBCPP_INLINE_VISIBILITY
     size_type max_bucket_count() const _NOEXCEPT
@@ -2351,15 +2353,17 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__equal_range_multi(
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
 void
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::swap(__hash_table& __u)
+#if _LIBCPP_STD_VER <= 11
     _NOEXCEPT_(
         __is_nothrow_swappable<hasher>::value && __is_nothrow_swappable<key_equal>::value
-#if _LIBCPP_STD_VER <= 11
         && (!allocator_traits<__pointer_allocator>::propagate_on_container_swap::value
               || __is_nothrow_swappable<__pointer_allocator>::value)
         && (!__node_traits::propagate_on_container_swap::value
               || __is_nothrow_swappable<__node_allocator>::value)
-#endif
             )
+#else
+  _NOEXCEPT_(__is_nothrow_swappable<hasher>::value && __is_nothrow_swappable<key_equal>::value)
+#endif
 {
     {
     __node_pointer_pointer __npp = __bucket_list_.release();

libcxx/include/__std_stream

@@ -276,7 +276,6 @@ __stdoutbuf<_CharT>::overflow(int_type __c)
             codecvt_base::result __r;
             char_type* pbase = &__1buf;
             char_type* pptr = pbase + 1;
-            char_type* epptr = pptr;
             do
             {
                 const char_type* __e;

libcxx/include/functional

@@ -2402,14 +2402,14 @@ struct _LIBCPP_TYPE_VIS_ONLY hash<long double>
                 size_t __b;
                 size_t __c;
                 size_t __d;
-            };
+            } __s;
         } __u;
-        __u.__a = 0;
-        __u.__b = 0;
-        __u.__c = 0;
-        __u.__d = 0;
+        __u.__s.__a = 0;
+        __u.__s.__b = 0;
+        __u.__s.__c = 0;
+        __u.__s.__d = 0;
         __u.__t = __v;
-        return __u.__a ^ __u.__b ^ __u.__c ^ __u.__d;
+        return __u.__s.__a ^ __u.__s.__b ^ __u.__s.__c ^ __u.__s.__d;
 #elif defined(__x86_64__)
         // Zero out padding bits
         union
@@ -2419,12 +2419,12 @@ struct _LIBCPP_TYPE_VIS_ONLY hash<long double>
             {
                 size_t __a;
                 size_t __b;
-            };
+            } __s;
         } __u;
-        __u.__a = 0;
-        __u.__b = 0;
+        __u.__s.__a = 0;
+        __u.__s.__b = 0;
         __u.__t = __v;
-        return __u.__a ^ __u.__b;
+        return __u.__s.__a ^ __u.__s.__b;
 #else
         return __scalar_hash<long double>::operator()(__v);
 #endif

libcxx/include/memory

@@ -3420,7 +3420,7 @@ struct __scalar_hash<_Tp, 2>
             {
                 size_t __a;
                 size_t __b;
-            };
+            } __s;
         } __u;
         __u.__t = __v;
         return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
@@ -3442,7 +3442,7 @@ struct __scalar_hash<_Tp, 3>
                 size_t __a;
                 size_t __b;
                 size_t __c;
-            };
+            } __s;
         } __u;
         __u.__t = __v;
         return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
@@ -3465,7 +3465,7 @@ struct __scalar_hash<_Tp, 4>
                 size_t __b;
                 size_t __c;
                 size_t __d;
-            };
+            } __s;
         } __u;
         __u.__t = __v;
         return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));

libcxx/include/string

@@ -1936,7 +1936,12 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string()
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 basic_string<_CharT, _Traits, _Allocator>::basic_string(const allocator_type& __a)
-    : __r_(__a)
+#if _LIBCPP_STD_VER <= 14
+        _NOEXCEPT_(is_nothrow_copy_constructible<allocator_type>::value)
+#else
+        _NOEXCEPT
+#endif
+: __r_(__a)
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->__insert_c(this);