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Author Topic: Program crashes on Windows 11 within Try Except  (Read 3225 times)

gicla

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Program crashes on Windows 11 within Try Except
« on: December 10, 2023, 05:27:23 pm »
Hi everybody,

After days trying to understand I decided to post here as I'm lost.
My program always ran fine on Windows10. Since a few months I upgraded to Windows 11 and now at all the Try...Except, in cas of errors it freezes instead of executing the Except clause.
Any hint please?

That's the code which hangs:
Code: Pascal  [Select][+][-]
  1.   // Verify Fields value type for M fields and MF or MD whitin approved messages
  2.         case UpperCase(copy(aFieldsDef[3, z], 1, 3)) of
  3.           'INT' : begin
  4.                     try
  5.                       iTestValue := StrToInt64(AnsiString(xmlDoc.DocumentElement.FindNode(aFieldsDef[1, z]).TextContent));
  6.                     except
  7.                       WriteError('Line: ' + sLine + ' | ' + xmlStr.DataString, 'ERROR: "' + AnsiString(aFieldsDef[1, z]) + '" value MUST be numeric, only digits allowed here.');
  8.                     end;
  9.                   end;
  10.           'STR' : begin
  11.  
  12.                   end;
  13.           'CON' : begin     { TODO : da eliminare e gestire }
  14.  
  15.                   end;
  16.           else MessageDlg('(' + AnsiString(sMsgType) + ') ' + AnsiString(aFieldsDef[1, z]) + ' - Wrong field type definition ' + '(' + UpperCase(copy(aFieldsDef[3, z],1,3)) + ')' + ' into the ini file.' + #10 + 'Allowed values are:' + #10 + '"STR" = String' + #10 + '"INT" = Numeric', mtWarning, [mbOK], 0);
  17.         end;
  18.  

I tried to inser the following test code in teh same procedure which hangs and it also hangs:
Code: Pascal  [Select][+][-]
  1.   divider := '0';
  2.   Try
  3.     Result := 5 div StrToInt(divider);
  4.   Except
  5.     showmessage('0 divide not possible');
  6.   end;
  7.  

However, the same sample code used in a different procedure, works just fine.

rvk

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Re: Program crashes on Windows 11 within Try Except
« Reply #1 on: December 10, 2023, 05:34:17 pm »
So what does WriteError do?

What happens if there is an exception in your except clause?

What happens after this code?

Just change the writeerror to
Code: Pascal  [Select][+][-]
  1. on E: exception do showmessage(e.message);
and you'll see the actual reason for the exception.
(Or run in the IDE and let it catch the exception)

Thaddy

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Re: Program crashes on Windows 11 within Try Except
« Reply #2 on: December 10, 2023, 06:52:08 pm »
Note EDivideByZero is one of the standard exceptions defined in sysutils.ou do noy want to rely on sysutils, because of its size, you can check for error 200.
« Last Edit: December 10, 2023, 06:56:34 pm by Thaddy »
Specialize a type, not a var.

PascalDragon

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Re: Program crashes on Windows 11 within Try Except
« Reply #3 on: December 10, 2023, 09:18:19 pm »
Note EDivideByZero is one of the standard exceptions defined in sysutils.ou do noy want to rely on sysutils, because of its size, you can check for error 200.

On Windows with SEH using tryexcept-blocks without using the SysUtils unit is currently (from 3.2.0 on) not fully supported anymore, because the SEH implementation is missing some functions to allow the usage without that unit.

Bart

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Re: Program crashes on Windows 11 within Try Except
« Reply #4 on: December 10, 2023, 10:05:03 pm »
On Windows with SEH using tryexcept-blocks without using the SysUtils unit is currently (from 3.2.0 on) not fully supported anymore, because the SEH implementation is missing some functions to allow the usage without that unit.
Is that documented somewhere?

Bart

dbannon

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Re: Program crashes on Windows 11 within Try Except
« Reply #5 on: December 10, 2023, 11:47:13 pm »
On Windows with SEH using tryexcept-blocks without using the SysUtils unit is currently (from 3.2.0 on) not fully supported anymore, because the SEH implementation is missing some functions to allow the usage without that unit.

Wow, that rings alarm bells, especially for Windows avoiders like me. SEH is a compiler option to Microsoft C (and incomplete with C++), so a FPC/Lazarus app would not be using SEH. Even MS seem to suggest its not a good thing. Is the warning from Pascal Dragon because we might be linked to libraries that do use SEH ?

By " not fully supported" do you mean it compiles but might not work ?  Does the compiler generate a Warning for example ?  Given that I do much of my "What if this happens" extreame testing in Linux, sounds like the exceptional events that might lead to an Exception might just crash my app on Windows unpredictably ?

Worried from Axedale
(Davo)
Lazarus 2, Linux (and reluctantly Win10, OSX)
My Project - https://github.com/tomboy-notes/tomboy-ng and my github - https://github.com/davidbannon

avra

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Re: Program crashes on Windows 11 within Try Except
« Reply #6 on: December 11, 2023, 07:22:42 am »
That's the code which hangs:
If you delete line 16 does it still hang?
ct2laz - Conversion between Lazarus and CodeTyphon
bithelpers - Bit manipulation for standard types
pasettimino - Siemens S7 PLC lib

ASerge

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Re: Program crashes on Windows 11 within Try Except
« Reply #7 on: December 11, 2023, 09:59:49 pm »
Code uses Dialogs.MessageDlg. Unit Dialogs include SysUtils, therefore, thoughts about the fact that SEH does not work without Sysutils in this topic can be discarded.
We need a minimal example of where the error would occur so that others can check it. Maybe the problem is elsewhere.

PascalDragon

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Re: Program crashes on Windows 11 within Try Except
« Reply #8 on: December 14, 2023, 09:54:52 pm »
On Windows with SEH using tryexcept-blocks without using the SysUtils unit is currently (from 3.2.0 on) not fully supported anymore, because the SEH implementation is missing some functions to allow the usage without that unit.
Is that documented somewhere?

No, because it's essentially a bug.

On Windows with SEH using tryexcept-blocks without using the SysUtils unit is currently (from 3.2.0 on) not fully supported anymore, because the SEH implementation is missing some functions to allow the usage without that unit.

Wow, that rings alarm bells, especially for Windows avoiders like me. SEH is a compiler option to Microsoft C (and incomplete with C++), so a FPC/Lazarus app would not be using SEH. Even MS seem to suggest its not a good thing. Is the warning from Pascal Dragon because we might be linked to libraries that do use SEH ?

Ehm... you are aware that SEH is the exception handling mechanism on Windows, used throughout the operating system and even across languages? The compiler option in MSVC is simply whether the conversion of SEH exceptions to C++ exceptions is enabled.

There's a reason after all that we switched from setjmp/longjmp based exception handling, because otherwise there were issues with exceptions that occurred in libraries that the executable captured while it shouldn't.

By " not fully supported" do you mean it compiles but might not work ?  Does the compiler generate a Warning for example ?  Given that I do much of my "What if this happens" extreame testing in Linux, sounds like the exceptional events that might lead to an Exception might just crash my app on Windows unpredictably ?

It means that it will compile, but an except-block might not be entered correctly if at all if an exception occurs.

dbannon

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Re: Program crashes on Windows 11 within Try Except
« Reply #9 on: December 15, 2023, 11:31:47 am »
....
Ehm... you are aware that SEH is the exception handling mechanism on Windows, used throughout the operating system and even across languages? The compiler option in MSVC is simply whether the conversion of SEH exceptions to C++ exceptions is enabled.
Nope !  I don't use Windows, I most certainly don't do any low level programming under windows. Thats why I use FPC/Lazarus.

.....
It means that it will compile, but an except-block might not be entered correctly if at all if an exception occurs.
Like I said, Wow.
So, quick grep through my code, only 36 "except on", less than I'd expect. But quite a variety.  Is there any point in testing ?  I mean, if I simulate, say an EXMLReadError and its correctly handled, can I assume it would always be correctly handled ?

David
Lazarus 2, Linux (and reluctantly Win10, OSX)
My Project - https://github.com/tomboy-notes/tomboy-ng and my github - https://github.com/davidbannon

gicla

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Re: Program crashes on Windows 11 within Try Except
« Reply #10 on: December 15, 2023, 03:05:39 pm »
Thank you all for your time and responses, let me give you some more info below:

@rvk
The "WriteError" procedures works just fine. When the program doesn't hang, due to the try...exept issue, WriteError does what it should do.
When there is an exception, instead of executing the code after "Except", the program hangs displaying the attached error.
If I move the same Try...Except code outside the procedure where it should run, it works as expected executing the "Except" clause .

@ASerge is correct. SysUtils is included

gicla

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Re: Program crashes on Windows 11 within Try Except
« Reply #11 on: December 15, 2023, 03:22:45 pm »
Let me add some additional info which, to me, makes this issue a little weirder:

The following code make the application hanging when executing the "Except" clause:
Code: Pascal  [Select][+][-]
  1. procedure TForm1.VerifyMandatoryFields;
  2. var
  3.   z, x, i, iSLIdx, iDummy : Integer;
  4.   iTestValue, Mytest : Int64;
  5.   sTmpNodeName : WideString;
  6.   sFldDim : String;
  7.   bDccChecked : Boolean;
  8.   OPIExpDate : TDateTime;
  9.   ExRate : Real;
  10.   dDummy : Double;
  11. begin
  12.   try
  13.     MyTest := StrToInt64('12z3568');
  14.   except
  15.     showmessage('Not a valid Int64 value');
  16.   end;
  17. end;
  18.  

While the following code works just fine:
Code: Pascal  [Select][+][-]
  1. procedure TForm1.VerifyMandatoryFields;
  2. var
  3.   z, x, i, iSLIdx, iDummy : Integer;
  4.   iTestValue, Mytest : Int64;
  5.   sTmpNodeName : WideString;
  6.   sFldDim : String;
  7.   bDccChecked : Boolean;
  8.   OPIExpDate : TDateTime;
  9.   ExRate : Real;
  10.   dDummy : Double;
  11. begin
  12.   if not TryStrToInt64('12z3568', Mytest) then showmessage('Not a valid Int64 value');
  13. end;
« Last Edit: December 15, 2023, 03:29:13 pm by gicla »

rvk

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Re: Program crashes on Windows 11 within Try Except
« Reply #12 on: December 15, 2023, 03:37:26 pm »
When and by what code is TForm1.VerifyMandatoryFields called?

What happens if you put this code in a Button1Click under a button?
Does it hang then too?

(I'm wondering if this code isn't called sitting a thread or something.)

gicla

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Re: Program crashes on Windows 11 within Try Except
« Reply #13 on: December 15, 2023, 05:56:10 pm »
When and by what code is TForm1.VerifyMandatoryFields called?

What happens if you put this code in a Button1Click under a button?
Does it hang then too?

(I'm wondering if this code isn't called sitting a thread or something.)

TForm1.LoadButtonClick event calls
|
|--> TForm1.AnalyzeLog which in turn calls
                        |
                        |--> TForm1.VerifyXMLHeaderExist
                        |--> TForm1.VerifyMandatoryFields


rvk

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Re: Program crashes on Windows 11 within Try Except
« Reply #14 on: December 15, 2023, 05:57:39 pm »
If the code also crashes in a simple ButtonClick then you can make a small project which reproduces the problem and it can be submitted as bugreport.

For me, this works without any problems on Linux Mint.

Code: Pascal  [Select][+][-]
  1. procedure TForm1.Button1Click(Sender: TObject);
  2. var
  3.   Mytest : Int64;
  4. begin
  5.   try
  6.     MyTest := StrToInt64('12z3568');
  7.   except
  8.     showmessage('Not a valid Int64 value');
  9.   end;
  10. end;
« Last Edit: December 15, 2023, 06:05:04 pm by rvk »

 

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