No longer reject inputs when using a locale that has grouping information _and_ the input has no grouping characters at all. We continue to reject cases when the input has grouping characters in the wrong place. Fixes PR#28704

llvm-svn: 362508

1 files changed, 3 insertions, 1 deletions

diff --git a/libcxx/src/locale.cpp b/libcxx/src/locale.cpp
index 00eb574ec45..ca0a1c9b15f 100644
--- a/libcxx/src/locale.cpp
+++ b/libcxx/src/locale.cpp
@@ -4379,7 +4379,9 @@ void
 __check_grouping(const string& __grouping, unsigned* __g, unsigned* __g_end,
                  ios_base::iostate& __err)
 {
-    if (__grouping.size() != 0)
+//  if the grouping pattern is empty _or_ there are no grouping bits, then do nothing
+//  we always have at least a single entry in [__g, __g_end); the end of the input sequence
+	if (__grouping.size() >= 0 && __g_end - __g > 1)
     {
         reverse(__g, __g_end);
         const char* __ig = __grouping.data();