[binutils-gdb] gdbsupport: use result_of_t instead of result_of in parallel-for.h

[Simon Marchi <simark@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=a09520cdd91a87ada081b065c42256bec2be6946

commit a09520cdd91a87ada081b065c42256bec2be6946
Author: Simon Marchi <simon.marchi@efficios.com>
Date:   Tue Apr 12 12:30:08 2022 -0400

    gdbsupport: use result_of_t instead of result_of in parallel-for.h
    
    When building with -std=c++11, I get:
    
    In file included from /home/smarchi/src/binutils-gdb/gdb/unittests/parallel-for-selftests.c:22:                                                                             /home/smarchi/src/binutils-gdb/gdb/../gdbsupport/parallel-for.h:134:10: error: ‘result_of_t’ is not a member of ‘std’; did you mean ‘result_of’?
      134 |     std::result_of_t<RangeFunction (RandomIt, RandomIt)>
          |          ^~~~~~~~~~~
          |          result_of
    
    This is because result_of_t has been introduced in C++14.  Use the
    equivalent result_of<...>::type instead.
    
    result_of and result_of_t have been removed in C++20 though, so I think
    we'll need some patches eventually to make the code use invoke_result
    instead, depending on the C++ version.
    
    Change-Id: I4817f361c0ebcdd4b32976898fc368bb302b61b9

Diff:
---
 gdbsupport/parallel-for.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/gdbsupport/parallel-for.h b/gdbsupport/parallel-for.h
index 44303abb716..713ec660306 100644
--- a/gdbsupport/parallel-for.h
+++ b/gdbsupport/parallel-for.h
@@ -131,13 +131,13 @@ private:
 
 template<class RandomIt, class RangeFunction>
 typename gdb::detail::par_for_accumulator<
-    std::result_of_t<RangeFunction (RandomIt, RandomIt)>
+    typename std::result_of<RangeFunction (RandomIt, RandomIt)>::type
   >::result_type
 parallel_for_each (unsigned n, RandomIt first, RandomIt last,
 		   RangeFunction callback)
 {
-  typedef typename std::result_of_t<RangeFunction (RandomIt, RandomIt)>
-    result_type;
+  using result_type
+    = typename std::result_of<RangeFunction (RandomIt, RandomIt)>::type;
 
   size_t n_threads = thread_pool::g_thread_pool->thread_count ();
   size_t n_elements = last - first;