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Report From: Delphi-BCB/Compiler/Delphi/Exceptions [ Add a report in this area ]

Report #: 106932

Status: Withdrawn

(Regression from Delphi 2010) Wrong exception handling for EExternalException (object leak and AV)

Project: Delphi

Build #: 16.0.4429.46931

Version: 16.4

Submitted By: Alexander Alexeev

Report Type: Basic functionality failure

Date Reported: 7/5/2012 3:53:12 PM

Severity: Serious / Highly visible problem

Last Updated: 7/5/2012 5:19:20 PM

Platform: All versions

Internal Tracking #:

Resolution: None

Resolved in Build: : None

Duplicate of: None

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Description

There is a bug in exception handling code of Delphi RTL for x86-32 which result in:
A). Memory leak.
B). Access violation.

Consider this code:

RaiseException(1, 0, 0, nil);

EExternalException object will be created for "RaiseException" call. However, it is not saved anywhere and will be lost. Instead, some trash values will be saved as Delphi object. This will cause AV later, when RTL will try to release exception object (AV will be raised by Free/Destroy call of TObject).

D7 - has no issue.
D2009 - has no issue.
D2010 - has no issue.
DXE - has issue.
DXE2 - has issue.

So, it seems that this behaviour was breaked during implementing cross-platform technologies in Delphi.

P.S. There is somehow similar issue that was fixed in the past: http://qc.embarcadero.com/wc/qcmain.aspx?d=3018

Steps to Reproduce:

1. Create new VCL project.
2. Place a button and add this code to OnClick:

RaiseException(1, 0, 0, nil);

3a. Run application under debugger.
4a. Click on button.
Expected: 1 debugger exception notificatons and a message box with "External exception 1" message.
Actual: 2 debugger exception notifications (external exception + access violation), no message box.

3b. Run application outside of debugger.
4b. Click on button.
Expected: error message box with "External exception 1" message.
Actual: no error message box.

Reproduce with attached project:
1. Open attached project.
2. Be sure that "Use Debug DCUs" option is enabled.
3. Open System unit.
4. Find _HandleFinally routine for x86-32.
5. Place a breakpoint on 4th line - "PUSH EBX".
6. Run the application and click on button.
7. Skip first debugger notification and wait for breakpoint hit.
8. Analyze exception record saved in EAX - it is wrong. See attached screenshot for more explanation.

Workarounds

None

Attachment

ExpBug.zip

Comments

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