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[Programming Help] - corruption of variables on simple code using standard arrays

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[2022-03-01 09:02:21] #1 [Go To First Post]
User824913 - Posts: 15
After a day of testing with one of my studies, I isolated a problem that I did not expect. Here I am repeating a simple code that shows the anomaly // The top of every source code file must include this line #include "sierrachart.h" SCDLLName("Provette") bool flag=false; int tempi[100]; int timeInMilliseconds; SCSFExport scsf_Provette(SCStudyInterfaceRef sc) { // Section 1 - Set the configuration variables and defaults if (sc.SetDefaults) { sc.GraphName = "Provette"; sc.AutoLoop = 1; //Automatic looping is enabled. sc.Subgraph[0].Name = "Name"; sc.Subgraph[0].DrawStyle = DRAWSTYLE_LINE; sc.Subgraph[0].PrimaryColor = RGB (0, 255, 0); sc.Input[0].Name = "Float Input"; sc.Input[0].SetFloat(0.0f); return; } SCString sTxt; sc.AddMessageToLog(sTxt.Format("flag--> %d",flag),0); int timeInMillisecondsTmp = sc.CurrentSystemDateTimeMS.GetTimeInMilliseconds(); int lassoTempo=timeInMillisecondsTmp-timeInMilliseconds; timeInMilliseconds=timeInMillisecondsTmp; tempi[0]=lassoTempo; double tTot=0; for (int i=99;i>=0;i--){ tempi[i+1]=tempi[i]; tTot=tTot+tempi[i]; } double tempoMedio=tTot/100.0; bool test=true; } In the first few cycles the flag variable has value 0 as one would expect, but after a few cycles its value becomes random and changes continuously. Where is the problem? thks a lot

[2022-03-01 12:06:47] #2 [Go To First Post]
1+1=10 - Posts: 270
It appears you never modify “flag” within this study. The only thing I can think of is that “flag” is a global variable. Thus, it gets shared between all the other studies within SCDLLName("Provette"). So if any other custom study modifies “flag” it would be seen by this study too. Date Time Of Last Edit: 2022-03-01 12:20:22

[2022-03-01 12:19:16] #3 [Go To First Post]
1+1=10 - Posts: 270
If this is your problem and you want data, specific to a study, to persist between cycles, you need to use persistent variables and/or dynamic memory allocations and/or sc.StorageBlock: ACSIL Interface Members - Functions: Persistent Variable Functions ACSIL Programming Concepts: Dynamic Memory Allocations Within Study Instance ACSIL Interface Members - Variables and Arrays: sc.StorageBlock

[2022-03-01 13:23:21] #4 [Go To First Post]
User907968 - Posts: 838
for (int i=99;i>=0;i--){ tempi[i+1]=tempi[i]; tTot=tTot+tempi[i]; There is an array bounds error during the first iteration of the for loop. iter 1: i = 99 therefore: i + 1 = 100 100 is beyond the end of the array, so this is undefined behavior.

[2022-03-01 13:26:27] #5 [Go To First Post]
1+1=10 - Posts: 270
@User907968 100 is beyond the end of the array, so this is undefined behavior. Nice catch.

[2022-03-01 15:10:26] #6 [Go To First Post]
User824913 - Posts: 15
Ufff... what a gross mistake. I lost a day without realizing it. Sorry, thanks

[2022-03-01 15:36:35] #7 [Go To First Post]
1+1=10 - Posts: 270
@User824913. It happens! I went to bed last night with a bug in my ACSIL that resulted from: // This is fine. if (....) x = 1; // In Python both statements would be inside the if but in C++ the 2nd statement is not. // Typically I'd catch this but I guess I was tired. if (....) x = 1; y = 2; // Not inside the if Anyway, good luck in your trading!

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