1 files changed, 21 insertions, 19 deletions

diff --git a/lib/dir_exist_async.h b/lib/dir_exist_async.h
index 7eb4827e..19e5f745 100644
--- a/lib/dir_exist_async.h
+++ b/lib/dir_exist_async.h
@@ -21,43 +21,44 @@ namespace
 //- check existence of all directories in parallel! (avoid adding up search times if multiple network drives are not reachable)
 //- add reasonable time-out time!
 //- avoid checking duplicate entries by design: set<Zstring, LessFilename>
-std::set<Zstring, LessFilename> getExistingDirsUpdating(const std::set<Zstring, LessFilename>& dirnames, bool allowUserInteraction, ProcessCallback& procCallback)
+std::set<Zstring, LessFilename> getExistingDirsUpdating(const std::set<Zstring, LessFilename>& dirnames,
+                                                        std::set<Zstring, LessFilename>& missing,
+                                                        bool allowUserInteraction,
+                                                        ProcessCallback& procCallback)
 {
     using namespace zen;
 
-    std::list<boost::unique_future<bool>> dirEx;
+    missing.clear();
 
-    std::for_each(dirnames.begin(), dirnames.end(),
-                  [&](const Zstring& dirname)
-    {
-        dirEx.push_back(zen::async2<bool>([=]() -> bool
+    std::list<std::pair<Zstring, boost::unique_future<bool>>> futureInfo;
+    for (const Zstring& dirname : dirnames)
+        if (!dirname.empty())
+            futureInfo.push_back(std::make_pair(dirname, async2<bool>([=]() -> bool
         {
-            if (dirname.empty())
-                return false;
 #ifdef ZEN_WIN
             //1. login to network share, if necessary
             loginNetworkShare(dirname, allowUserInteraction);
 #endif
             //2. check dir existence
             return dirExists(dirname);
-        }));
-    });
+        })));
 
     std::set<Zstring, LessFilename> output;
     //don't wait (almost) endlessly like win32 would on not existing network shares:
     const boost::system_time endTime = boost::get_system_time() + boost::posix_time::seconds(20); //consider CD-rom insert or hard disk spin up time from sleep
 
-    auto itDirname = dirnames.begin();
-    for (auto it = dirEx.begin(); it != dirEx.end(); (void)++it, ++itDirname) //void: prevent ADL from dragging in boost's ,-overload: "MSVC warning C4913: user defined binary operator ',' exists but no overload could convert all operands"
+    for (auto& fi : futureInfo)
     {
-        procCallback.reportStatus(replaceCpy(_("Searching for folder %x..."), L"%x", fmtFileName(*itDirname), false)); //may throw!
+        procCallback.reportStatus(replaceCpy(_("Searching for folder %x..."), L"%x", fmtFileName(fi.first), false)); //may throw!
 
         while (boost::get_system_time() < endTime &&
-               !it->timed_wait(boost::posix_time::milliseconds(UI_UPDATE_INTERVAL / 2)))
+               !fi.second.timed_wait(boost::posix_time::milliseconds(UI_UPDATE_INTERVAL / 2)))
             procCallback.requestUiRefresh(); //may throw!
 
-        if (it->is_ready() && it->get())
-            output.insert(*itDirname);
+        if (fi.second.is_ready() && fi.second.get())
+            output.insert(fi.first);
+        else
+            missing.insert(fi.first);
     }
     return output;
 }
@@ -66,9 +67,10 @@ std::set<Zstring, LessFilename> getExistingDirsUpdating(const std::set<Zstring,
 inline //also silences Clang "unused function" for compilation units depending from getExistingDirsUpdating() only
 bool dirExistsUpdating(const Zstring& dirname, bool allowUserInteraction, ProcessCallback& procCallback)
 {
-    std::set<Zstring, LessFilename> dirnames;
-    dirnames.insert(dirname);
-    std::set<Zstring, LessFilename> dirsEx = getExistingDirsUpdating(dirnames, allowUserInteraction, procCallback);
+    if (dirname.empty()) return false;
+    std::set<Zstring, LessFilename> missing;
+    std::set<Zstring, LessFilename> dirsEx = getExistingDirsUpdating({ dirname }, missing, allowUserInteraction, procCallback);
+    assert(dirsEx.empty() != missing.empty());
     return dirsEx.find(dirname) != dirsEx.end();
 }
 }