Re: [ft-devel] suspicious code in FT_Set_Renderer

[Tom Bishop, Wenlin Institute]

On Dec 12, 2010, at 9:13 PM, Werner LEMBERG wrote:

> 
>> While browsing freetype code I notice following code in
>> FT_Set_Renderer (src/base/ftobjs.c, v2.4.4 release):
>> 
>>    if ( num_params > 0 )
>>    {
>>      FT_Renderer_SetModeFunc  set_mode = renderer->clazz->set_mode;
>> 
>> 
>>      for ( ; num_params > 0; num_params-- )
>>      {
>>        error = set_mode( renderer, parameters->tag, parameters->data );
>>        if ( error )
>>          break;
>>      }
>>    }
>> 
>> I believe that iteration over parameters expected here. Like:
>> 
>> --- src/base/ftobjs.c        (old)
>> +++ src/base/ftobjs.c        (new)
>> @@ -3887,6 +3887,7 @@
>>         error = set_mode( renderer, parameters->tag, parameters->data );
>>         if ( error )
>>           break;
>> +        parameters++;
>>       }
>>     }
> 
> Have you seen the `num_params--' in the `for' loop?  It starts with
> num_params, then comes num_params-1, num_params-2, etc.

Still, why call set_mode() repeatedly if renderer and parameters are the same 
each time? FT_Set_Renderer() seems to expect parameters[] to be an array with 
num_params elements, but only the first element, parameters[0], is being 
accessed. It looks suspiciously like the code is missing "parameters++" as the 
original poster suggested. Maybe the code is supposed to be equivalent to the 
following:

FT_UInt i;
for (i = 0; i < num_params; i++)
  set_mode( renderer, parameters[i].tag, parameters[i].data );

(Unless there's a reason for doing the last parameter first?)

Tom

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