[committed] libstdc++: Simplify basic_string_view::ends_with [PR 101361]

[Jonathan Wakely]

The use of npos triggers a diagnostic as described in PR c++/101361.
This change replaces the use of npos with the exact length, which is
already known. We can further simplify it by inlining the effects of
compare and substr, avoiding the redundant range checks in the latter.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	PR c++/101361
	* include/std/string_view (ends_with): Use traits_type::compare
	directly.

Tested powerpc64le-linux. Committed to trunk.

-------------- next part --------------
commit 4d3eaeb4f505b0838c673ee28e7dba8687fc8272
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Jul 13 12:21:27 2021

    libstdc++: Simplify basic_string_view::ends_with [PR 101361]
    
    The use of npos triggers a diagnostic as described in PR c++/101361.
    This change replaces the use of npos with the exact length, which is
    already known. We can further simplify it by inlining the effects of
    compare and substr, avoiding the redundant range checks in the latter.
    
    Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
    
    libstdc++-v3/ChangeLog:
    
            PR c++/101361
            * include/std/string_view (ends_with): Use traits_type::compare
            directly.

diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view
index cfdcf28f026..4ea72c6cef2 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -361,8 +361,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       constexpr bool
       ends_with(basic_string_view __x) const noexcept
       {
-	return this->size() >= __x.size()
-	    && this->compare(this->size() - __x.size(), npos, __x) == 0;
+	const auto __len = this->size();
+	const auto __xlen = __x.size();
+	return __len >= __xlen
+	  && traits_type::compare(end() - __xlen, __x.data(), __xlen) == 0;
       }
 
       constexpr bool