Problem when iCustom is called with an empty string

[Forex Trader]

Metatrader 4 build 201
Metaeditor build 200

I think there is a problem when we call the iCustom function with a string parameter and when this parameter is an empty string ("").

In this case, Metatrader will not respond. I join 2 very simple programs to reproduce this problem. As these examples are very simple, Metatrader does not respond during 10 seconds, but in more complex indicator, it does not respond for much more.

To reproduce the bug, copy "A" an "B" programs in indicator section.
1) Display "A" (with default input parameters) in Metatrader. You will note that Metatrader is frozen during 10 seconds.
2) remove "A" from the chart and display it again but this time, fill the user parameter <e_input_data> (which is a string type) with something (what you want). In this case, Metatrader does not freeze.


The problem in 1) comes from the iCustom call that takes the <e_input_data> parameter which is an empty string (""). And I do not konw why, but iCustom does not like these empty strings...


Program "A.mq4" :

//+---------------------------------------------------------+
//|                                                   A.mq4 
//|                                                       
//|                                                        
//|  This program shows a bug in Metatrader 4 build 201:  
//|  we call the program "B" through a iCustom call with  
//|  an empty string parameter.                          
//|                                                       
//+---------------------------------------------------------+
#property indicator_chart_window
#property indicator_buffers 1
#property indicator_color1 Blue





//************************************************************
// Input parameters
//************************************************************

extern int    e_period       = 14;
extern int    e_type_ma      = MODE_SMA;
extern int    e_type_data    = PRICE_CLOSE;
extern string e_input_data   = "";



//---- output buffer
double ExtOutputBuffer[];


int init()
{ 
   IndicatorBuffers( 1 );
   SetIndexBuffer( 0, ExtOutputBuffer );
   SetIndexStyle( 0, DRAW_LINE, STYLE_SOLID, 2 );

   
   IndicatorShortName( "A" );  
   SetIndexLabel( 0, "A" ); 

   return( 0 );
}

int deinit()
{
   return(0);
}


int start()
{
   int countedBars=IndicatorCounted();


   //---- check for possible errors
   if( countedBars < 0 ) 
   {
      return(-1);
   }
   
   _computeLastNbBars( Bars - countedBars - 1 );  

   return( 0 );
}


void _computeLastNbBars( int lastBars )
{
   int pos;
   
        
   for( pos = lastBars; pos >= 0; pos-- )
         ExtOutputBuffer[pos] = iCustom( NULL, 0, "B", e_period, e_type_ma, e_type_data, e_input_data, 0, pos );
}

Program "B.mq4" :

//+---------------------------------------------------------+
//|                                                   B.mq4
//|                                  
//|                                     
//|  This program shows a bug in Metatrader 4 build 201: 
//|  we call the program "B" through a iCustom call with 
//|  an empty string parameter.                          
//|                                                     
//|                                                     
//+---------------------------------------------------------+
#property indicator_chart_window
#property indicator_buffers 1
#property indicator_color1 Red


//---- output buffer
double ExtOutputBuffer[];



//************************************************************
// Input parameters
//************************************************************

extern int    e_period       = 14;
extern int    e_type_ma      = MODE_SMA;
extern int    e_type_data    = PRICE_CLOSE;
extern string e_input_data   = "";

int init()
{ 
   IndicatorBuffers( 1 );
   SetIndexBuffer( 0, ExtOutputBuffer );
   SetIndexStyle( 0, DRAW_LINE, STYLE_SOLID, 2 );

   
   IndicatorShortName( "B" );  
   SetIndexLabel( 0, "B" ); 

   return( 0 );
}

int deinit()
{
   return(0);
}

int start()
{
   int countedBars=IndicatorCounted();


   //---- check for possible errors
   if( countedBars < 0 ) 
   {
      return(-1);
   }
   
   _computeLastNbBars( Bars - countedBars - 1 );  

   return( 0 );
}

void _computeLastNbBars( int lastBars )
{
   int pos;
           
   for( pos = lastBars; pos >= 0; pos-- )
      ExtOutputBuffer[pos] = iMA( NULL, 0, e_period, 0, e_type_ma, e_type_data, pos);
}