Re: exception handling, function call and memory
* George2:
Such code segment is used to check whether function call or exception-
handling mechanism runs out of memory first (written by Bjarne),
[Code]
void perverted()
{
try{
throw exception();
}
catch (exception& e)
{
perverted();
cout << e.what() << endl;
}
}
[/Code]
1.
My question is when the exception is thrown, and goes to exception
handler in catch block, it will do operations in the following
sequences,
(1) execute the exception handler code (since there will be recursive
function call -- stack will ever increasing);
(2) unwind stack.
From the C++ view, ignoring details of how exception handling is
implemented at the machine code level (e.g. double stack walk), a
'throw' results in stack unwinding followed by execution of 'catch'
code, if there is a matching 'catch'.
Runs out of memory because function call will make stack ever-
increasing, right?
From an academic point of view that depends on optimization. A
compiler could conceivably detect that the above is an infinite
recursion doing nothing. In practice it will run out of memory.
If it does (2) before (1), I think stack will always be unwinded
before exception handling is called -- then stack will never grow, so
there will be no out-of-memory caused by an ever increasing stack.
Is that correct?
No. In the code above the "stack unwinding" is only locally within the
function call, essentially doing nothing, not back to a call of the
function.
2.
I am confused about why exception handling mechanism will run out of
memory because in exception handle implementation, we just insert
exception handler registration block of the function onto the
beginning of the new function call stack each time there is a function
call, so the memory should be the memory consumed by function call
stuff, I do not think exception handling mechanism itself will consume
additional memory. How do you think of it and how do you think of the
what are the memory consumed by exception handling mechanism?
Whether a 'try' consumes memory depends on the implementation.
Cheers, & hth.,
- Alf
PS: George, could you please start giving references for your quotes and
parahprases, and also, please start reading the groups you post to.
--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?