KWSys 2017-12-12 (3ba214b7)

Code extracted from:

    https://gitlab.kitware.com/utils/kwsys.git

at commit 3ba214b7963fdd59f6f230c100550f9c5aa3deab (master).

Upstream Shortlog
-----------------

Gregor Jasny (1):
      8e029751 SystemTools: Fix IsSubDirectory for subdirs of drive root

1 files changed, 9 insertions, 4 deletions

diff --git a/SystemTools.cxx b/SystemTools.cxx
index 50aa857..649f30b 100644
--- a/SystemTools.cxx
+++ b/SystemTools.cxx
@@ -4234,11 +4234,16 @@ bool SystemTools::IsSubDirectory(const std::string& cSubdir,
   std::string dir = cDir;
   SystemTools::ConvertToUnixSlashes(subdir);
   SystemTools::ConvertToUnixSlashes(dir);
-  if (subdir.size() > dir.size() && subdir[dir.size()] == '/') {
-    std::string s = subdir.substr(0, dir.size());
-    return SystemTools::ComparePath(s, dir);
+  if (subdir.size() <= dir.size() || dir.empty()) {
+    return false;
   }
-  return false;
+  bool isRootPath = *dir.rbegin() == '/'; // like "/" or "C:/"
+  size_t expectedSlashPosition = isRootPath ? dir.size() - 1u : dir.size();
+  if (subdir[expectedSlashPosition] != '/') {
+    return false;
+  }
+  std::string s = subdir.substr(0, dir.size());
+  return SystemTools::ComparePath(s, dir);
 }
 
 void SystemTools::Delay(unsigned int msec)