[libc++] Enable -Wunused-template

Clang wants to enable this flag by default, but libc++ isn't working with it yet.

Reviewed By: Mordante, #libc, #libc_abi, EricWF

Spies: libcxx-commits, arichardson

Differential Revision: https://reviews.llvm.org/D144667

8 files changed, 43 insertions, 17 deletions

diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 0c1b2fe32f7a..ed9aaf60f255 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -568,9 +568,15 @@ function(cxx_add_warning_flags target)
   else()
     target_add_compile_flags_if_supported(${target} PRIVATE -Wall)
   endif()
-  target_add_compile_flags_if_supported(${target} PRIVATE -Wextra -W -Wwrite-strings
-                                                          -Wno-unused-parameter -Wno-long-long
-                                                          -Werror=return-type -Wextra-semi -Wundef
+  target_add_compile_flags_if_supported(${target} PRIVATE -Wextra
+                                                          -W
+                                                          -Wwrite-strings
+                                                          -Wno-unused-parameter
+                                                          -Wno-long-long
+                                                          -Werror=return-type
+                                                          -Wextra-semi
+                                                          -Wundef
+                                                          -Wunused-template
                                                           -Wformat-nonliteral)
   if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
     target_add_compile_flags_if_supported(${target} PRIVATE
diff --git a/libcxx/include/__algorithm/make_projected.h b/libcxx/include/__algorithm/make_projected.h
index f4ca4c9d4a7a..61055fcdf30d 100644
--- a/libcxx/include/__algorithm/make_projected.h
+++ b/libcxx/include/__algorithm/make_projected.h
@@ -60,7 +60,7 @@ template <class _Pred,
           __enable_if_t<!(!is_member_pointer<typename decay<_Pred>::type>::value &&
                             __is_identity<typename decay<_Proj>::type>::value),
                         int> = 0>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR static _ProjectedPred<_Pred, _Proj>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ProjectedPred<_Pred, _Proj>
 __make_projected(_Pred& __pred, _Proj& __proj) {
   return _ProjectedPred<_Pred, _Proj>(__pred, __proj);
 }
@@ -73,7 +73,7 @@ template <class _Pred,
           __enable_if_t<!is_member_pointer<typename decay<_Pred>::type>::value &&
                           __is_identity<typename decay<_Proj>::type>::value,
                         int> = 0>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR static _Pred& __make_projected(_Pred& __pred, _Proj&) {
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Pred& __make_projected(_Pred& __pred, _Proj&) {
   return __pred;
 }
 
@@ -86,7 +86,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 namespace ranges {
 
 template <class _Comp, class _Proj1, class _Proj2>
-_LIBCPP_HIDE_FROM_ABI constexpr static
+_LIBCPP_HIDE_FROM_ABI constexpr
 decltype(auto) __make_projected_comp(_Comp& __comp, _Proj1& __proj1, _Proj2& __proj2) {
   if constexpr (__is_identity<decay_t<_Proj1>>::value && __is_identity<decay_t<_Proj2>>::value &&
                 !is_member_pointer_v<decay_t<_Comp>>) {
diff --git a/libcxx/include/__config b/libcxx/include/__config
index 95a75ea758d5..d3063f039a89 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -1254,13 +1254,19 @@ _LIBCPP_BEGIN_NAMESPACE_STD _LIBCPP_END_NAMESPACE_STD
 // macro is used to mark them as such, which suppresses the
 // '-Wctad-maybe-unsupported' compiler warning when CTAD is used in user code
 // with these classes.
-#if _LIBCPP_STD_VER >= 17
-#    define _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(_ClassName)                                                                \
-      template <class ..._Tag>                                                                                         \
-      _ClassName(typename _Tag::__allow_ctad...) -> _ClassName<_Tag...>
-#else
-#  define _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(_ClassName) static_assert(true, "")
-#endif
+#  if _LIBCPP_STD_VER >= 17
+#    ifdef _LIBCPP_COMPILER_CLANG_BASED
+#      define _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(_ClassName)                                                              \
+        template <class... _Tag>                                                                                       \
+        [[maybe_unused]] _ClassName(typename _Tag::__allow_ctad...)->_ClassName<_Tag...>
+#    else
+#      define _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(ClassName)                                                               \
+        template <class... _Tag>                                                                                       \
+        ClassName(typename _Tag::__allow_ctad...)->ClassName<_Tag...>
+#    endif
+#  else
+#    define _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(_ClassName) static_assert(true, "")
+#  endif
 
 // TODO(varconst): currently, there are bugs in Clang's intrinsics when handling Objective-C++ `id`, so don't use
 // compiler intrinsics in the Objective-C++ mode.
diff --git a/libcxx/include/__memory/shared_ptr.h b/libcxx/include/__memory/shared_ptr.h
index 3ef264dcfe48..70615176d370 100644
--- a/libcxx/include/__memory/shared_ptr.h
+++ b/libcxx/include/__memory/shared_ptr.h
@@ -433,10 +433,10 @@ struct __is_array_deletable<_Ptr, decltype(delete[] std::declval<_Ptr>())> : tru
 
 template <class _Dp, class _Pt,
     class = decltype(std::declval<_Dp>()(std::declval<_Pt>()))>
-static true_type __well_formed_deleter_test(int);
+true_type __well_formed_deleter_test(int);
 
 template <class, class>
-static false_type __well_formed_deleter_test(...);
+false_type __well_formed_deleter_test(...);
 
 template <class _Dp, class _Pt>
 struct __well_formed_deleter : decltype(std::__well_formed_deleter_test<_Dp, _Pt>(0)) {};
diff --git a/libcxx/include/__type_traits/is_nothrow_convertible.h b/libcxx/include/__type_traits/is_nothrow_convertible.h
index 148c2d68ccab..64f75e1fd68d 100644
--- a/libcxx/include/__type_traits/is_nothrow_convertible.h
+++ b/libcxx/include/__type_traits/is_nothrow_convertible.h
@@ -27,10 +27,10 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 #if _LIBCPP_STD_VER >= 20
 
 template <typename _Tp>
-static void __test_noexcept(_Tp) noexcept;
+void __test_noexcept(_Tp) noexcept;
 
 template<typename _Fm, typename _To>
-static bool_constant<noexcept(_VSTD::__test_noexcept<_To>(std::declval<_Fm>()))>
+bool_constant<noexcept(_VSTD::__test_noexcept<_To>(std::declval<_Fm>()))>
 __is_nothrow_convertible_test();
 
 template <typename _Fm, typename _To>
diff --git a/libcxx/src/filesystem/filesystem_common.h b/libcxx/src/filesystem/filesystem_common.h
index fb6f88783cd0..5867805efeee 100644
--- a/libcxx/src/filesystem/filesystem_common.h
+++ b/libcxx/src/filesystem/filesystem_common.h
@@ -44,9 +44,11 @@
 #endif
 #endif
 
+// TODO: Check whether these functions actually need internal linkage, or if they can be made normal header functions
 _LIBCPP_DIAGNOSTIC_PUSH
 _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wunused-function")
 _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wunused-function")
+_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wunused-template")
 
 #if defined(_LIBCPP_WIN32API)
 #  define PATHSTR(x) (L##x)
diff --git a/libcxx/utils/libcxx/test/params.py b/libcxx/utils/libcxx/test/params.py
index 0574a00a737b..db4c5efc08a0 100644
--- a/libcxx/utils/libcxx/test/params.py
+++ b/libcxx/utils/libcxx/test/params.py
@@ -17,6 +17,7 @@ _warningFlags = [
   '-Wextra',
   '-Wshadow',
   '-Wundef',
+  '-Wunused-template',
   '-Wno-unused-command-line-argument',
   '-Wno-attributes',
   '-Wno-pessimizing-move',
diff --git a/libcxxabi/src/demangle/StringView.h b/libcxxabi/src/demangle/StringView.h
index 90890e377110..07b7cf857575 100644
--- a/libcxxabi/src/demangle/StringView.h
+++ b/libcxxabi/src/demangle/StringView.h
@@ -17,9 +17,16 @@
 #define DEMANGLE_STRINGVIEW_H
 
 #include "DemangleConfig.h"
+
+#include <__cxxabi_config.h>
 #include <cassert>
 #include <cstring>
 
+#ifdef _LIBCXXABI_COMPILER_CLANG
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-template"
+#endif
+
 DEMANGLE_NAMESPACE_BEGIN
 
 class StringView {
@@ -119,4 +126,8 @@ inline bool operator==(const StringView &LHS, const StringView &RHS) {
 
 DEMANGLE_NAMESPACE_END
 
+#ifdef _LIBCXXABI_COMPILER_CLANG
+#pragma clang diagnostic pop
+#endif
+
 #endif