qt-bugs@ issue : none
Trolltech task ID : none yet
bugs.kde.org number : None
applied: no
author: Dirk Mueller <mueller@kde.org>

in big user environments, getgrgid_r() needs more memory than sysconf() returns.
Try a bit harder.

--- src/corelib/io/qfsfileengine_unix.cpp
+++ src/corelib/io/qfsfileengine_unix.cpp
@@ -845,9 +845,16 @@
     } else if (own == OwnerGroup) {
         struct group *gr = 0;
 #if !defined(QT_NO_THREAD) && defined(_POSIX_THREAD_SAFE_FUNCTIONS) && !defined(Q_OS_OPENBSD)
-        buf.resize(sysconf(_SC_GETGR_R_SIZE_MAX));
-        struct group entry;
-        getgrgid_r(ownerId(own), &entry, buf.data(), buf.size(), &gr);
+        for (unsigned size = sysconf(_SC_GETGR_R_SIZE_MAX); size < 256000; size += size)
+        {
+            buf.resize(size);
+            struct group entry;
+            // ERANGE indicates that the buffer was too small
+            if (!getgrgid_r(ownerId(own), &entry, buf.data(), buf.size(), &gr)
+                || errno != ERANGE)
+                break;
+        }
+
 #else
         gr = getgrgid(ownerId(own));
 #endif