RE: [Flightgear-devel] try ... catch ... throw (up)

2005-11-12 Thread Jon Berndt 
> Vassilii Khachaturov wrote:

> I am unsure it is OK to through a temporary object like this.
> It's created on the stack right there at the same frame where it's thrown,
> but IIRC, as throw unwinds the stack, it is auto-destructed. You should
> be throwing an object that has lifetime encompassing the outer catch
> handler.

Ah! Yes, that sounds correct. I'll have to go back and change my throws.

Thanks,

Jon


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Re: [Flightgear-devel] try ... catch ... throw (up)

2005-11-12 Thread Vassilii Khachaturov 
> Here's what I'm doing:
>
> In the Table class:
>
> In FGTable constructor:
>
> if (operation_types.find(parent_type) == string::npos) {
>   internal = true;
> } else {
>   throw(string("An internal table cannot be ..."));
> }
>
> Now, this seems to work OK - I throw an exception if a situation
> occurs that is invalid.
[snip]
> I'm probably missing something fundamental here. Anyone have any suggestions?
>
> Jon

I am unsure it is OK to through a temporary object like this.
It's created on the stack right there at the same frame where it's thrown,
but IIRC, as throw unwinds the stack, it is auto-destructed. You should
be throwing an object that has lifetime encompassing the outer catch
handler.



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[Flightgear-devel] try ... catch ... throw (up)

2005-11-11 Thread Jon Berndt 
I've been trying to use exception handling in a particularly appropriate place 
in JSBSim,
but am having little success, and it's got me confused.

I have a section where I am reading in some data. If it is inappropriate, I 
need to let
the user know and exit.

Here's what I'm doing:

In the Table class:

In FGTable constructor:

if (operation_types.find(parent_type) == string::npos) {
  internal = true;
} else {
  throw(string("An internal table cannot be ..."));
}

Now, this seems to work OK - I throw an exception if a situation occurs that is 
invalid.

Here's where the above code is originally called from:

In FGFunction constructor:

try {
  Parameters.push_back(new FGTable(PropertyManager, element));
} catch (...) {throw;}

This is supposed to pass the exception on up the chain to here the code that 
calls the
above:

In FGAerodynamics::Load():

try {
  variables.push_back( new FGFunction(PropertyManager, function_element) );
} catch(string msg) {
  return false;
}

Execution seems to get to the "throw" in FGFunction and dies. Execution never 
gets to the
handler in FGAerodynamics. I get a segfault.

I'm probably missing something fundamental here. Anyone have any suggestions?

Jon


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