avoid multiple reallocations in wxString::PrintfV() if vsnprintf() returns the total required size

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@36303 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/string.cpp

@@ -1836,14 +1836,20 @@ int wxString::PrintfV(const wxChar* pszFormat, va_list argptr)
         // vsnprintf() may return either -1 (traditional Unix behaviour) or the
         // total number of characters which would have been written if the
         // buffer were large enough (newer standards such as Unix98)
-        if ( len >= 0 && len <= size )
+        if ( len < 0 )
+        {
+            // still not enough, as we don't know how much we need, double the
+            // current size of the buffer
+            size *= 2;
+        }
+        else if ( len > size )
+        {
+            size = len;
+        }
+        else // ok, there was enough space
         {
-            // ok, there was enough space
             break;
         }
-
-        // still not enough, double it again
-        size *= 2;
     }
 
     // we could have overshot