Re: [boost] Question for C++experts aboutexception allocationfailure

Subject: Re: [boost] Question for C++experts aboutexception allocationfailure
From: Sebastian Redl (sebastian.redl_at_[hidden])
Date: 2009-05-19 03:23:23

On Tue, 19 May 2009 07:37:26 +0200, "Adam Badura" <abadura_at_[hidden]> wrote:
>> Here's a perfectly legal, perfectly defined C++03 program in a single
>> module with a single thread that has a runtime-determined number of
>> exceptions:
>>
>> #include <iostream>
>>
>> void fun(int recursions);
>>
>> int main()
>> {
>>  int n;
>>  std::cin >> n;
>>  fun(n);
>> }
>>
>> void fun(int recursions) {
>>  try {
>>    throw 0;
>>  } catch(int) {
>>    fun(recursions - 1);
>>  }
>> }
> 
>     Actually you must use the exception object in the catch so that the 
> compiler cannot optimize it away. So this example is not correct. :)

Just because the compiler *can*, doesn't mean that it does. In fact, I very
much doubt you'll find a compiler that does. Exception handling is
partially implemented in support libraries, and dealing with disappearing
exception objects is hard for a library. So it's still likely
runtime-determined.
The compiler could also analyze the program and determine that it's one big
noop and completely optimize it away, except for the input statement.

But by all means, print the int or use a type with a non-trivial
constructor as the exception. My point is made, and nit-picking won't
change that.

Sebastian