Re: [Boost-users] [multiprecision] noexcept() usage in gmp int

Subject: Re: [Boost-users] [multiprecision] noexcept() usage in gmp int
From: Francesco Biscani (bluescarni_at_[hidden])
Date: 2013-06-16 18:06:11

Thank you John!

Best regards,

  Francesco.

On 14 June 2013 13:41, John Maddock <john_at_[hidden]> wrote:

> I was trying out the new multiprecision library (kudos!), and I ran into a
>> problem. In order to make certain guarantees in my code regarding
>> exception
>> safety, I am mandating that types being used in generic containers are
>> marked noexcept() for certain basic operations (namely, destruction and
>> move operations).
>>
>> It seems like this is generally guaranteed in the multiprecision library
>> (tried with cpp_int and the mpfr adaptor), with the important exception of
>> the gmp integer class. A glance at the headers reveals that (gmp.hpp):
>>
>> //
>> // Within this file, the only functions we mark as noexcept are those that
>> manipulate
>> // (but don't create) an mpf_t.  All other types may allocate at pretty
>> much any time
>> // via a user-supplied allocator, and therefore throw.
>> //
>>
>> Additionally, browsing the gmp documentation yields this snippet (
>> http://gmplib.org/manual/**Custom-Allocation.html
>

>> ):
>>
>> """
>> There's currently no defined way for the allocation functions to recover
>> from an error such as out of memory, they must terminate program
>> execution.
>> A longjmp or throwing a C++ exception will have undefined results. This
>> may
>> change in the future.
>> """
>>
>> Would it be possible then for the mp library authors to consider adding
>> basic noexcept() guarantees to the gmp adaptor class in future versions?
>>
>
> Looks like an oversight to me, added BOOST_NOEXCEPT to mpz_int
> destruct/move/swap operations in Trunk.
>
> On a related note, these noexcept specifications seem to be untestable to
> me, am I missing something?
>
> John.
> ______________________________**_________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/**mailman/listinfo.cgi/boost-**users
>
>