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Groups > comp.lang.c++.moderated > #1420

Re: codecvt problem

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On 2011-06-08 16:24, Vaclav Haisman wrote:
> Martin Bonner wrote, On 8.6.2011 10:06:
>>
>> But memset produces undefined behaviour if mbstate_t is (for example)
>> void *.  I /think/ the only way to fix this is something like:
> Why does it produce undefined behaviour? You can always take address of a
> void pointer and zero the pointer.

That has never been guaranteed by either the C or the C++ standard:
the object representation that has all zero bits does not necessarily
yield the value representation of a null pointer.

Nevertheless, the habit of "using memset for everything" seems to be
quite widespread, which I consider an abomination.

>> namespace { mbstate_t zerostate; }
>> int main () { mbstate_t mystate = zerostate;...}
>>
>> But that's an awful faf.
> That would be usable. Ideal would be if we had some
> std::mbstate_init(mbstate_t &) function or similar.

Or an initializer macro could be better, as in:

    pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

What we need ideally is not an initialization function or initializer
macro for each type whose variable needs to be initialized, but a uniform
syntax to initialize a variable of any type. That's what the C++0x uniform
initializer syntax brought to us. Unfortunately, that came too late,
and we have different sets of available methods in C, C++03, and C++0x,
and initializing an object of an opaque type has become a pain.

-- 
Seungbeom Kim


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Thread

codecvt problem  Rafał Moniuszko <rafal.lists@gmail.com> - 2011-06-05 07:25 -0600
  Re: codecvt problem Vaclav Haisman <v.haisman@sh.cvut.cz> - 2011-06-05 21:41 -0600
    Re: codecvt problem  Jeff Flinn <TriumphSprint2000@hotmail.com> - 2011-06-06 12:50 -0600
      Re: codecvt problem Vaclav Haisman <v.haisman@sh.cvut.cz> - 2011-06-06 15:31 -0600
        Re: codecvt problem  Martin Bonner <martinfrompi@yahoo.co.uk> - 2011-06-08 02:06 -0600
          Re: codecvt problem  Vaclav Haisman <v.haisman@sh.cvut.cz> - 2011-06-08 17:24 -0600
            Re: codecvt problem  Seungbeom Kim <musiphil@bawi.org> - 2011-06-09 07:02 -0600
              Re: codecvt problem Vaclav Haisman <v.haisman@sh.cvut.cz> - 2011-06-16 17:04 -0600
                Re: codecvt problem Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2011-06-17 06:42 -0600
                Re: codecvt problem Seungbeom Kim <musiphil@bawi.org> - 2011-06-18 07:38 -0600
                Re: codecvt problem Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2011-06-20 13:16 -0600
                Re: codecvt problem Seungbeom Kim <musiphil@bawi.org> - 2011-06-23 14:42 -0600
        Re: codecvt problem  Seungbeom Kim <musiphil@bawi.org> - 2011-06-09 07:01 -0600
      Re: codecvt problem Daniel Krügler <daniel.kruegler@googlemail.com> - 2011-06-06 15:31 -0600
        Re: codecvt problem Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2011-06-07 03:07 -0600
          Re: codecvt problem  Daniel Krügler <daniel.kruegler@googlemail.com> - 2011-06-07 10:31 -0600
  Re: codecvt problem  Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2011-06-06 12:47 -0600

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