Hi,

I have tried to google for "External: SIGSEGV" exception, but nothing what came up helped.

Is there any detailed explanation about when this exception occurs?

In my program it pops up when reading an unassigned (nil) object property:

  MyObject2_Var:= MyObject1.MyObject2;   (MyObject1.MyObject2 is nil)

The strange thing is that the assignment is in a try ... except block, and the debugger does not stop at the breakpoints in the exception handling part.

I am totally clueless.

Thanks for reading

- Leslie -

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It's from gdb debugger . Search for "SIGSEV gdb" and I'm sure you will find much more.

It may be a bug in gdb ..I don't know, but if debugger is trying to access some memory which MyObject2_Var is pointing to and it's not accessible then....

I am totally clueless.

Me too sometimes. Debugging with Lazarus under windows really need a total rebuild with native debugger, but it looks like hopeless wish now...

Regards
Boguslaw

Jon Foster wrote

SIGSEGV (otherwise known as a segfault) is a *nix signal indicating that the an illegal address was accessed. Normally it can't be caught with a try...except. You have to muck about with signals to catch it with try ... except.

This is not correct.
The RTL catches this signal and converts this to an exception, if you use the sysutils unit.

Michael.

Maybe posting some more code will help to find an answer.

Mattias

My advice: test program outside of the Lazarus IDE.If it crashes then
it's not an IDE, but I suspect it's all about gdb.

Regards
Boguslaw

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Thanks to All of You who have tried to help!.

I have located the problem and found a solution, but was not able to reproduce it yet in a separate test app.

The structure of the code looked like this:

MyObj = class;
private
   Obj1: TOtherObj;
   Obj2: TOtherObj;

. . .

end;
procedure T_Main.Button1Click(Sender: TObject);
begin
   with Obj1 do begin
       SomeProcedure(Obj2);
   end;
end;
The exception occurred while reading "Obj2";

The problem completely disappeared after removing the "with ..." block, which was actually unnecessary junk code since no Obj1 property or method was used in that block.

I am not sure, but Obj1 and Ojb2 being of the same type, and Obj1 not being used may have had something to do with it. Just guessing. :)

I will try to make a bug report, when I will be able to reproduce the bug.

Thanks for your help again!

- Leslie -

For some reason the linespacing was doubled after pasting the text of the e-mail (from Word) through the clipboard.

The structure of the code looked like this:

 T_Main = class(TForm);
...
private
   Obj1: TOtherObj;
   Obj2: TOtherObj;
. . .
end;
procedure T_Main.Button1Click(Sender: TObject);
begin
   with Obj1 do
   begin
       SomeProcedure(Obj2);
   end;
end;

Did you tried to compile program and run outside of the IDE ? Still crashing ?

Boguslaw

Did you tried to compile program and run outside of the IDE ? Still crashing ?

Yes. The same exception every time.

My guess is that the compiler used the object in the "with" line instead of the the object it should have used within the block. The referenced property in the first object was unassigned, so the SigSegv exeption would be appropriate there.

- Leslie -

Have you tried the fpc 2.3.1?

Mattias

Have you tried the fpc 2.3.1?

Have not installed it yet. I had the impression that it was a bit risky to use it.

- Leslie -