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Report From: Delphi-BCB/Debugger/Evaluator [ Add a report in this area ]

Report #: 7457

Status: Closed

Inspecting large arrays causes the Delphi IDE to hang

Project: Delphi

Build #: N/A

Version: 10.0

Submitted By: Vimil Varghese

Report Type: Crash / Data loss / Total failure

Date Reported: 2/28/2004 9:47:16 PM

Severity: Infrequently encountered problem

Last Updated: 3/20/2012 2:24:39 AM

Platform: All versions

Internal Tracking #: 238702

Resolution: Fixed (Resolution Comments)

Resolved in Build: : 10.0.2279.20311

Duplicate of: None

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Description

1)create the following types

type
  TIntegerArray=array[0..(maxint)div sizeof(integer)-1] of Integer;
  PIntegerArray=^TIntegerArray;

2) create a variable of type PIntegerArray
3) allocate some memory to it using GetMem
4) assign a value to some element of the array.

#1 procedure TForm1.Button1Click(Sender: TObject);
#2 var
#3  a:PIntegerArray;
#4 begin
#5  GetMem(a,4*sizeof(integer));
#6  a[0]:=3;
#7  form1.caption:=inttostr(a[3]);
#8 end;

5) Place a breakpoint at the line in which the array is accessed ie on line 6

6) Run the application

7) When the breakpoint triggers, Select Evaluate/Modify menuitem from the Run Menu

8) In the expression field type the following
    PIntegerArray(a)^

9) Click on the Inspect button

The Delphi IDE will now hang.

This is because Delphi trys to allocate 2GB
[(maxint)div sizeof(integer) bytes] of data to display all elements of the array.

This is not at all necessary. Even if it were possible to allocate 2GB of memory, our monitor screens are not big enough to display all the 2GB of the data at a time.

Although we would like to see the elements of the array, we do not want to see all the elements of the array at a time.

The Inspector should act like a window into the array, allocating memory for only a small number of elements.

It should show only a specified range of elements of the array,Scrolling should reposition this window so that a different portion of the array becomes visible.

Steps to Reproduce:

I was able to reproduce this with a 100000 element integer array.  I have attached a test case.  Follow steps 5-8 and click Evaluate (rather than Inspect) and the IDE will crash.

---
[QC Steps]
1)create the following types

type
  TIntegerArray=array[0..(maxint)div sizeof(integer)-1] of Integer;
  PIntegerArray=^TIntegerArray;

2) create a variable of type PIntegerArray
3) allocate some memory to it using GetMem
4) assign a value to some element of the array.

#1 procedure TForm1.Button1Click(Sender: TObject);
#2 var
#3  a:PIntegerArray;
#4 begin
#5  GetMem(a,4*sizeof(integer));
#6  a[0]:=3;
#7  form1.caption:=inttostr(a[3]);
#8 end;

5) Place a breakpoint at the line in which the array is accessed ie on line 6

6) Run the application

7) When the breakpoint triggers, Select Evaluate/Modify menuitem from the Run Menu

8) In the expression field type the following
    PIntegerArray(a)^

9) Click on the Inspect button

The Delphi IDE will now hang.

Workarounds

None

Attachment

None

Comments

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