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Re: Has "stack overflow" specified behavior?

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Paavo Helde <eesnimi@osa.pri.ee> writes:

> 12.12.2021 10:42 wij kirjutas:
>
>> void t() {
>>    int a;
>>    ++a;
>>    t();
>> };
>>
>> int main()
>> {
>>   t();
>> }
>>
>> ---
>> Has "stack overflow" specified behavior?
>
> No.  Stack overflow is arguably the least specified behavior of them
> all.  The stack size is extremely limited (few MB), compared to the
> RAM amounts current computers have (tens of GB).  There is no
> standard-defined way to detect stack overflow, not to speak about
> handling it.  That's one reason why using stack-allocated things
> like std::array needs special care, especially when writing
> libraries (which need to execute in a stack of unknown size and
> fill-up).
>
> There are some implementation-defined ways though to survive stack
> overflows, but it's not so easy.  You cannot continue the program if
> there is no more stack space, so the only way is to throw an
> exception.  Alas, there is no "throw" statement in the code, so this
> would be an "asynchronous" exception appearing at a pretty random
> place in the code, meaning that the compiler must cope with such
> exceptions, which may easily slow down the whole program (witness
> the /EHa compiler option in MSVC).
>
> BTW, your example code is not guaranteed to cause stack overflow, it
> might go into an infinite loop instead because of tail recursion, or
> become a zero op by optimizing the whole t() function away, either
> as UB or as a code with no effect.

It's important to distinguish the two realms of abstract machine
and actual machine.  In the abstract machine, the program shown
above (after fixing the problem of reading an uninitialized
variable) does have a well-defined specification, and the program
as a whole has defined behavior.  Whether a program has defined
behavior or undefined behavior is determined solely by what goes
on in the abstract machine (which may depend on values read from
a file or other input device, etc, but still the question is to
be answered considering only what happens in the abstract
machine, with reference to any actual machine).  Everything the
program does has a well-defined specification, and so the program
has only defined behavior, and no undefined behavior.

In an actual machine, an implementation is obliged to carry out
the abstract semantics only to the extent that the execution
does not exceed the implementation's "resource limits", which
might be anything at all, including stack space.  Once such a
resource limit is exceeded, the implementation has no further
obligations, and may abort, or whatever.  But that isn't the
same as undefined behavior, which depends solely on what the
standard says about operations in the abstract machine.

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Has "stack overflow" specified behavior? wij <wyniijj@gmail.com> - 2021-12-12 00:42 -0800
  Re: Has "stack overflow" specified behavior? Bonita Montero <Bonita.Montero@gmail.com> - 2021-12-12 09:52 +0100
    Re: Has "stack overflow" specified behavior? red floyd <no.spam.here@its.invalid> - 2021-12-12 12:59 -0800
  Re: Has "stack overflow" specified behavior? Paavo Helde <eesnimi@osa.pri.ee> - 2021-12-13 01:51 +0200
    Re: Has "stack overflow" specified behavior? Juha Nieminen <nospam@thanks.invalid> - 2021-12-13 05:48 +0000
      Re: Has "stack overflow" specified behavior? Bo Persson <bo@bo-persson.se> - 2021-12-13 10:44 +0100
        Re: Has "stack overflow" specified behavior? wij <wyniijj@gmail.com> - 2021-12-13 04:44 -0800
        Re: Has "stack overflow" specified behavior? Richard Damon <Richard@Damon-Family.org> - 2021-12-13 07:47 -0500
          Re: Has "stack overflow" specified behavior? Bonita Montero <Bonita.Montero@gmail.com> - 2021-12-14 08:32 +0100
            Re: Has "stack overflow" specified behavior? Richard Damon <Richard@Damon-Family.org> - 2021-12-14 07:49 -0500
              Re: Has "stack overflow" specified behavior? scott@slp53.sl.home (Scott Lurndal) - 2021-12-14 14:23 +0000
              Re: Has "stack overflow" specified behavior? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-12-14 16:16 +0100
        Re: Has "stack overflow" specified behavior? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-12-13 12:13 -0500
          Re: Has "stack overflow" specified behavior? Öö Tiib <ootiib@hot.ee> - 2021-12-13 12:05 -0800
            Re: Has "stack overflow" specified behavior? "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2021-12-13 17:11 -0800
            Re: Has "stack overflow" specified behavior? "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2021-12-13 19:00 -0800
              Re: Has "stack overflow" specified behavior? Öö Tiib <ootiib@hot.ee> - 2021-12-13 23:03 -0800
          Re: Has "stack overflow" specified behavior? Bonita Montero <Bonita.Montero@gmail.com> - 2021-12-14 08:33 +0100
            Re: Has "stack overflow" specified behavior? David Brown <david.brown@hesbynett.no> - 2021-12-14 09:13 +0100
              Re: Has "stack overflow" specified behavior? Juha Nieminen <nospam@thanks.invalid> - 2021-12-14 10:09 +0000
                Re: Has "stack overflow" specified behavior? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-12-14 16:14 +0000
                Re: Has "stack overflow" specified behavior? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-12-14 15:23 -0800
              Re: Has "stack overflow" specified behavior? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-12-14 16:10 +0000
              Re: Has "stack overflow" specified behavior? Bonita Montero <Bonita.Montero@gmail.com> - 2021-12-14 17:38 +0100
                Re: Has "stack overflow" specified behavior? scott@slp53.sl.home (Scott Lurndal) - 2021-12-14 17:09 +0000
                Re: Has "stack overflow" specified behavior? Bonita Montero <Bonita.Montero@gmail.com> - 2021-12-14 18:39 +0100
                Re: Has "stack overflow" specified behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-14 11:01 -0800
              Re: Has "stack overflow" specified behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-14 10:52 -0800
                Re: Has "stack overflow" specified behavior? David Brown <david.brown@hesbynett.no> - 2021-12-14 20:15 +0100
            Re: Has "stack overflow" specified behavior? Richard Damon <Richard@Damon-Family.org> - 2021-12-14 07:59 -0500
          Re: Has "stack overflow" specified behavior? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-12-14 16:19 +0100
            Re: Has "stack overflow" specified behavior? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-12-14 11:33 -0500
      Re: Has "stack overflow" specified behavior? Manfred <noname@add.invalid> - 2021-12-13 17:23 +0100
      Re: Has "stack overflow" specified behavior? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2021-12-15 23:27 +0000
        Re: Has "stack overflow" specified behavior? David Brown <david.brown@hesbynett.no> - 2021-12-16 08:37 +0100
    Re: Has "stack overflow" specified behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-13 14:16 -0800
      Re: Has "stack overflow" specified behavior? wij <wyniijj@gmail.com> - 2021-12-13 15:07 -0800
        Re: Has "stack overflow" specified behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-16 05:53 -0800
          Re: Has "stack overflow" specified behavior? wij <wyniijj@gmail.com> - 2021-12-16 08:34 -0800
            Re: Has "stack overflow" specified behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-16 12:17 -0800
              Re: Has "stack overflow" specified behavior? wij <wyniijj@gmail.com> - 2021-12-16 13:38 -0800
                Re: Has "stack overflow" specified behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-16 14:15 -0800
            Re: Has "stack overflow" specified behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-16 20:10 -0800
          Re: Has "stack overflow" specified behavior? Öö Tiib <ootiib@hot.ee> - 2021-12-16 14:14 -0800
            Re: Has "stack overflow" specified behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-16 20:20 -0800
              Re: Has "stack overflow" specified behavior? Öö Tiib <ootiib@hot.ee> - 2021-12-17 08:46 -0800
      Re: Has "stack overflow" specified behavior? Paavo Helde <eesnimi@osa.pri.ee> - 2021-12-14 10:32 +0200
        Re: Has "stack overflow" specified behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-16 07:42 -0800
          Re: Has "stack overflow" specified behavior? Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2021-12-17 01:07 +0000
            Re: Has "stack overflow" specified behavior? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-12-17 01:28 +0000
            Re: Has "stack overflow" specified behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-16 19:54 -0800
              Re: Has "stack overflow" specified behavior? Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2021-12-17 10:06 +0000
  Re: Has "stack overflow" specified behavior? Manfred <noname@add.invalid> - 2021-12-13 17:08 +0100
    Re: Has "stack overflow" specified behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-13 13:50 -0800
      Re: Has "stack overflow" specified behavior? Manfred <noname@add.invalid> - 2021-12-14 16:32 +0100
  Re: Has "stack overflow" specified behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-13 13:13 -0800
  Re: Has "stack overflow" specified behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-13 15:55 -0800
    Re: Has "stack overflow" specified behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-13 15:58 -0800
    Re: Has "stack overflow" specified behavior? wij <wyniijj@gmail.com> - 2021-12-14 01:41 -0800

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