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

[Jonathan Wakely via Gcc-patches]

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.

Tested powerpc64le-linux. Committed to trunk.

This needs to be backported to gcc-9 and gcc-10 too.


commit 49ff88bd0d8a36a9e903f01ce05685cfe07dee5d
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Tue Sep 22 20:02:58 2020

    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.

diff --git a/libstdc++-v3/src/c++17/fs_path.cc 
b/libstdc++-v3/src/c++17/fs_path.cc
index cea7aa08601..6e907b1c54d 100644
--- a/libstdc++-v3/src/c++17/fs_path.cc
+++ b/libstdc++-v3/src/c++17/fs_path.cc
@@ -81,7 +81,7 @@ struct path::_Parser
     const size_t len = input.size();
 
     // look for root name or root directory
-    if (is_dir_sep(input[0]))
+    if (len && is_dir_sep(input[0]))
       {
 #if SLASHSLASH_IS_ROOTNAME
        // look for root name, such as "//foo"
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();
 }