[libcxx-commits] [libcxx] 26068c6 - [libc++] <type_traits>: Avoid instantiating a pointer type.

[John Baldwin via libcxx-commits]

Author: John Baldwin
Date: 2022-11-21T14:34:08-08:00
New Revision: 26068c6e60324ed866a1ca2afb5cb5eb0aaf015b

URL: https://github.com/llvm/llvm-project/commit/26068c6e60324ed866a1ca2afb5cb5eb0aaf015b
DIFF: https://github.com/llvm/llvm-project/commit/26068c6e60324ed866a1ca2afb5cb5eb0aaf015b.diff

LOG: [libc++] <type_traits>: Avoid instantiating a pointer type.

GCC expands the pointer type in this conditional expression even for
template types _Up that are not arrays.  This raises an error when
std::decay<> is used with reference types (as is done in LLVM's
sources).  Using add_pointer<> causes GCC to only instantiate a
pointer type for array types.

Reviewed By: #libc, philnik, ldionne

Differential Revision: https://reviews.llvm.org/D135469

Added: 
    

Modified: 
    libcxx/include/__type_traits/decay.h
    libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/decay.pass.cpp

Removed: 
    


################################################################################
diff  --git a/libcxx/include/__type_traits/decay.h b/libcxx/include/__type_traits/decay.h
index c38bbdeff21b0..f45d33b8fb4bd 100644
--- a/libcxx/include/__type_traits/decay.h
+++ b/libcxx/include/__type_traits/decay.h
@@ -42,7 +42,7 @@ struct __decay<_Up, true> {
     typedef _LIBCPP_NODEBUG typename conditional
                      <
                          is_array<_Up>::value,
-                         __remove_extent_t<_Up>*,
+                         __add_pointer_t<__remove_extent_t<_Up> >,
                          typename conditional
                          <
                               is_function<_Up>::value,

diff  --git a/libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/decay.pass.cpp b/libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/decay.pass.cpp
index af9915488f475..d07a136a59475 100644
--- a/libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/decay.pass.cpp
+++ b/libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/decay.pass.cpp
@@ -29,10 +29,14 @@ int main(int, char**)
     test_decay<int, int>();
     test_decay<const volatile int, int>();
     test_decay<int*, int*>();
+    test_decay<int&, int>();
+    test_decay<const volatile int&, int>();
     test_decay<int[3], int*>();
     test_decay<const int[3], const int*>();
     test_decay<void(), void (*)()>();
 #if TEST_STD_VER > 11
+    test_decay<int&&, int>();
+    test_decay<const volatile int&&, int>();
     test_decay<int(int) const, int(int) const>();
     test_decay<int(int) volatile, int(int) volatile>();
     test_decay<int(int)  &, int(int)  &>();