How to avoid array out of range - mql4

Question

Does somebody know how to avoid the error array out of range when trying to display long number of bars (lets say 7000) in an indicator buffer?

Answer 1

I had a similar issue, that I always got "Array out of range" errors for one of my buffers. I checked with ArraySize(), which returned 0. In the end I just forgot to call SetIndexBuffer(...) for this buffer array in onInit() {...} of my indicator.
Since I was using an internal buffer without drawing lines, I used the IndicatorBuffers() function to increase the amount of buffers first and then registered my additonal buffer using SetIndexBuffer(...).
//+------------------------------------------------------------------+
//| Custom indicator initialization function |
//+------------------------------------------------------------------+
int OnInit()
{
//--- indicator buffers mapping
IndicatorBuffers(5);
//buffers with #properties settings
SetIndexBuffer(0,Buffer1);
SetIndexBuffer(1,Buffer2);
SetIndexBuffer(2,Buffer3);
SetIndexBuffer(3,Buffer4);
//additional buffer without #properties
SetIndexBuffer(4,AdditionalBuffer);

Answer 2

While the arrays (problem) look similar, there is a major difference
MQL4 Indicators use "other" mechanics for handling arrays than "ordinary" arrays have.
... Testing pass stopped due to a critical error in the EA
... array out of range in '!2015-09-08___!EA 2xAMA 01 2015-09-08_msMOD_0.00.mq4' (519,39)
Yes, MT4 throws Fatal Error on an attempt to handle a wrong ptr->array[aStaticSIZE] and one has to take due care to either avoid such case, or trim ptr ( alike in low-latency circular-buffer scenarios ) not to direct past the array boundary ( underflow / overflow ) or extend the array[] via ArrayResize() so as to keep pace with the ptr growth ( until memory allows ) ) on arrays declared as dynamic double Array[];, however MQL4 Technical Indicators have completely other situation.
Limits? Yes. . . . . . ( And one ought to review on each New-MQL4.56789 stealth update )
As of a "New"-MQL4.56789-Build-840, your "ordinary" array cannot have more than 2.147.483.647 elements, if O/S memory-pool manager allows, so you ought to have plenty of space, even if using higher dimensionality mappings { 2D | 3D | 4D }.
Years ago 've used many parallel 2D / 3D-arrays for fast and private ( safely encapsulated ) heap / stack-handlers for maintaining highly dynamic entities in scales of 100k+ rows / 2D-planes and all worked well-oiled in old-MQL4.
So some 7k+ elements should not make you any worries.
Indicators use array indirectly, via an automated Buffer-handler
In this sense, your code need not care about these issues.
/*
#property "pragmas" help MQL4-compiler decide about setup of internal handlers
so this part of code "speaks" to MetaLang.exe at compile-time*/
#property indicator_buffers 3 // .DEF N-Buffs
#property indicator_color1 White // .SET Buf[0].color
#property indicator_color2 SeaGreen // .SET Buf[1].color
#property indicator_color3 FireBrick // .SET Buf[2].color
#property indicator_width1 1 // .SET Buf[0].width
#property indicator_width2 2 // .SET Buf[1].width
#property indicator_width3 2 // .SET Buf[2].width
double buffer_line_up[], // .DEF Arrays as dynamic ...[]
buffer_line_dn[], // with human-readable-names
buffer_line_ax[]; // and MT4 will take care
int init() {
SetIndexBuffer( 0, buffer_line_ax ); // .ASSOC IndexBuffer.0<-array[]
SetIndexLabel( 0, "SuperTrend" );
SetIndexBuffer( 1, buffer_line_up ); // .ASSOC IndexBuffer.0<-array[]
SetIndexLabel( 1, "Up Trend" );
SetIndexStyle( 1, DRAW_LINE,
STYLE_SOLID,
1 + int( ATR_Multiplier / 5 ),
SeaGreen
);
SetIndexBuffer( 2, buffer_line_dn ); // .ASSOC IndexBuffer.0<-array[]
SetIndexLabel( 2, "Down Trend" );
SetIndexStyle( 2, DRAW_LINE,
STYLE_SOLID,
1 + int( ATR_Multiplier / 5 ),
FireBrick
);
SetIndexDrawBegin(0, ATR_Period ); // .DEF initial depth of Buffer before 1st GUI output
IndicatorShortName( "xxxx[" + ATR_Period + "," + ATR_Multiplier + "]" );
IndicatorDigits( MarketInfo( Symbol(), MODE_DIGITS ) );