msi: Comparisons with null in conditions are special.

dlls/msi/cond.y

@@ -445,46 +445,91 @@ static INT compare_substring( LPCWSTR a, INT operator, LPCWSTR b )
     return 0;
 }
 
+static BOOL is_empty( LPCWSTR p )
+{
+    return !p || !p[0];
+}
+
+static BOOL is_alphaless( LPCWSTR p )
+{
+    while (*p)
+    {
+        if (isalphaW( *p ) || (*p == '_'))
+             return FALSE;
+        p++;
+    }
+    return TRUE;
+}
+
 static INT compare_string( LPCWSTR a, INT operator, LPCWSTR b )
 {
+    int r;
+
     if (operator >= COND_SS && operator <= COND_RHS)
         return compare_substring( a, operator, b );
 
+    if (is_empty( a ) && is_empty( b ))
+        r = 0;
+
+    else if (is_empty( a ) && is_alphaless( b ))
+        r = 1;
+
+    else if (is_empty( b ) && is_alphaless( a ))
+        r = -1;
+
+    else
+    {
         /* null and empty string are equivalent */
         if (!a) a = szEmpty;
         if (!b) b = szEmpty;
 
-    /* a or b may be NULL */
         switch (operator)
         {
         case COND_LT:
-        return -1 == lstrcmpW( a, b );
         case COND_GT:
-        return  1 == lstrcmpW( a, b );
         case COND_EQ:
-        return  0 == lstrcmpW( a, b );
         case COND_NE:
-        return  0 != lstrcmpW( a, b );
         case COND_GE:
-        return -1 != lstrcmpW( a, b );
         case COND_LE:
-        return  1 != lstrcmpW( a, b );
+            r = lstrcmpW( a, b );
+            break;
         case COND_ILT:
-        return -1 == lstrcmpiW( a, b );
         case COND_IGT:
-        return  1 == lstrcmpiW( a, b );
         case COND_IEQ:
-        return  0 == lstrcmpiW( a, b );
         case COND_INE:
-        return  0 != lstrcmpiW( a, b );
         case COND_IGE:
-        return -1 != lstrcmpiW( a, b );
         case COND_ILE:
-        return  1 != lstrcmpiW( a, b );
+            r = lstrcmpiW( a, b );
+            break;
         default:
             ERR("invalid string operator\n");
             return 0;
         }
+    }
+
+    switch (operator)
+    {
+    case COND_LT:
+    case COND_ILT:
+        return -1 == r;
+    case COND_GT:
+    case COND_IGT:
+        return  1 == r;
+    case COND_EQ:
+    case COND_IEQ:
+        return  0 == r;
+    case COND_NE:
+    case COND_INE:
+        return  0 != r;
+    case COND_GE:
+    case COND_IGE:
+        return -1 != r;
+    case COND_LE:
+    case COND_ILE:
+        return  1 != r;
+    default:
+        ERR("invalid string operator\n");
+    }
     return 0;
 }