libstdc++: Fix out-of-bounds string_view access in filesystem::path [PR 97167]

libstdc++-v3/ChangeLog:

	PR libstdc++/97167
	* src/c++17/fs_path.cc (path::_Parser::root_path()): Check
	for empty string before inspecting the first character.
	* testsuite/27_io/filesystem/path/append/source.cc: Append
	empty string_view to path.

1 files changed, 10 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/27_io/filesystem/path/append/source.cc b/libstdc++-v3/testsuite/27_io/filesystem/path/append/source.cc
index 2fceee9b774..dc7331945fe 100644
--- a/libstdc++-v3/testsuite/27_io/filesystem/path/append/source.cc
+++ b/libstdc++-v3/testsuite/27_io/filesystem/path/append/source.cc
@@ -161,6 +161,15 @@ test06()
   test(p2, s.c_str());
 }
 
+void
+test07()
+{
+  path p, p0;
+  std::string_view s;
+  p /= s; // PR libstdc++/97167
+  compare_paths(p, p0);
+}
+
 int
 main()
 {
@@ -170,4 +179,5 @@ main()
   test04();
   test05();
   test06();
+  test07();
 }