Index: src/main.c
==================================================================
--- src/main.c
+++ src/main.c
@@ -1824,10 +1824,11 @@
 ){
   int rc = SQLITE_OK;
   unsigned int flags = *pFlags;
   const char *zVfs = zDefaultVfs;
   char *zFile;
+  char c;
   int nUri = sqlite3Strlen30(zUri);
 
   assert( *pzErrMsg==0 );
 
   if( ((flags & SQLITE_OPEN_URI) || sqlite3GlobalConfig.bOpenUri) 
@@ -1871,12 +1872,12 @@
     **   0: Parsing file-name.
     **   1: Parsing name section of a name=value query parameter.
     **   2: Parsing value section of a name=value query parameter.
     */
     eState = 0;
-    while( zUri[iIn] && zUri[iIn]!='#' ){
-      char c = zUri[iIn++];
+    while( (c = zUri[iIn])!=0 && c!='#' ){
+      iIn++;
       if( c=='%' 
        && sqlite3Isxdigit(zUri[iIn]) 
        && sqlite3Isxdigit(zUri[iIn+1]) 
       ){
         int octet = (sqlite3HexToInt(zUri[iIn++]) << 4);
@@ -1886,14 +1887,14 @@
         if( octet==0 ){
           /* This branch is taken when "%00" appears within the URI. In this
           ** case we ignore all text in the remainder of the path, name or
           ** value currently being parsed. So ignore the current character
           ** and skip to the next "?", "=" or "&", as appropriate. */
-          while( zUri[iIn] && zUri[iIn]!='#' 
-              && (eState!=0 || zUri[iIn]!='?')
-              && (eState!=1 || (zUri[iIn]!='=' && zUri[iIn]!='&'))
-              && (eState!=2 || zUri[iIn]!='&')
+          while( (c = zUri[iIn])!=0 && c!='#' 
+              && (eState!=0 || c!='?')
+              && (eState!=1 || (c!='=' && c!='&'))
+              && (eState!=2 || c!='&')
           ){
             iIn++;
           }
           continue;
         }
@@ -1981,10 +1982,12 @@
             *pzErrMsg = sqlite3_mprintf("no such %s mode: %s", zModeType, zVal);
             rc = SQLITE_ERROR;
             goto parse_uri_out;
           }
           if( mode>limit ){
+            *pzErrMsg = sqlite3_mprintf("%s mode not allowed: %s",
+                                        zModeType, zVal);
             rc = SQLITE_PERM;
             goto parse_uri_out;
           }
           flags = (flags & ~mask) | mode;
         }