[committed] libstdc++: Fix narrowing conversion in std/time/clock/utc/io.cc

[Jonathan Wakely via Gcc-patches]

Tested x86_64-linux, and verified with -fsigned-char -fshort-wchar
(which makes the underlying type of wchar_t be unsigned short).

Nightstrike also tested on mingw-w64.

Pushed to trunk.

-- >8 --

For a port with signed char and unsigned wchar_t initializing a wchar_t
array with a char is a narrowing conversion. The code is wrong for
assuming that (int)'a' == (int)L'a' anyway, so fix it properly by using
ctype<wchar_t>::widen(char).

libstdc++-v3/ChangeLog:

        * testsuite/std/time/clock/utc/io.cc: Use ctype to widen char.
---
 libstdc++-v3/testsuite/std/time/clock/utc/io.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/testsuite/std/time/clock/utc/io.cc 
b/libstdc++-v3/testsuite/std/time/clock/utc/io.cc
index b327c7f50c7..933cba65f44 100644
--- a/libstdc++-v3/testsuite/std/time/clock/utc/io.cc
+++ b/libstdc++-v3/testsuite/std/time/clock/utc/io.cc
@@ -46,6 +46,7 @@ test_format()
 
   std::ostringstream ss;
   std::wostringstream wss;
+  const auto& ct = std::use_facet<std::ctype<wchar_t>>(wss.getloc());
 
   for (char c : specs)
   {
@@ -68,7 +69,7 @@ test_format()
                    "required by the chrono-specs") != s.npos);
     }
 
-    wchar_t wfmt[] = { L'{', L':', L'%', c, L'}' };
+    wchar_t wfmt[] = { L'{', L':', L'%', ct.widen(c), L'}' };
     try
     {
       wss << std::vformat(std::wstring_view(wfmt, 5),
-- 
2.39.0