Re: Automatic strings without malloc

From	David Brown <david.brown@hesbynett.no>
Newsgroups	comp.lang.c
Subject	Re: Automatic strings without malloc
Date	2021-11-18 23:19 +0100
Organization	A noiseless patient Spider
Message-ID	<sn6jgl$val$1@dont-email.me> (permalink)
References	<sn2lvp$sl7$1@dont-email.me> <chine.bleu-14C4A8.12251018112021@reader.eternal-september.org>

Show all headers | View raw

On 18/11/2021 21:25, Siri Cruise wrote:
> In article <sn2lvp$sl7$1@dont-email.me>,
>  pozz <pozzugno@gmail.com> wrote:
> 
>> Many times I need to construct a string through a call to sprintf and 
>> pass it to an external function.
> 
> If it's too crippled to have malloc, you can do your own. Many 
> systems have blank common or bss after the end of all memory 
> initialised with code and data. You might even have the extern 
> address 'edata' for the bss start and 'end' for bss end. If so 
> you can use that as a heap:

It is not a matter of a system not having "malloc" and a heap - it is a
matter of deciding not to use it.  In small systems with limited ram and
no paging mechanisms, it is quite realistic to either run out of heap
space or - worse, since it is harder to find by testing - for heap
fragmentation to mean that memory allocations may fail as there is not
enough consecutive free space.  And in embedded systems, failure to get
the memory you need often means failure of the system - the device does
not do its job.

Thus a 0 return from malloc can be as bad as a string buffer overflow or
any other error - the system is broken, the car crashes, the microwave
burns your food, the washing machine eats your socks.  And while you can
avoid the string buffer overflow by making sure your buffer is large
enough and your string is limited in length, making sure your heap can
/never/ get fragmented is typically either extremely difficult, or
impossible.  The solution is to avoid dynamic memory in any situation
where failure to get the memory is not tolerable.

Thread

Automatic strings without malloc pozz <pozzugno@gmail.com> - 2021-11-17 11:36 +0100
  Re: Automatic strings without malloc pozz <pozzugno@gmail.com> - 2021-11-17 11:38 +0100
  Re: Automatic strings without malloc Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-11-17 03:00 -0800
  Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-17 12:04 +0100
    Re: Automatic strings without malloc Manfred <noname@add.invalid> - 2021-11-17 18:19 +0100
      Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-17 20:34 +0100
    Re: Automatic strings without malloc pozz <pozzugno@gmail.com> - 2021-11-18 10:07 +0100
  Re: Automatic strings without malloc Thiago Adams <thiago.adams@gmail.com> - 2021-11-17 05:11 -0800
    Re: Automatic strings without malloc Philipp Klaus Krause <pkk@spth.de> - 2021-11-18 15:29 +0100
  Re: Automatic strings without malloc Bart <bc@freeuk.com> - 2021-11-17 13:47 +0000
  Re: Automatic strings without malloc scott@slp53.sl.home (Scott Lurndal) - 2021-11-17 15:34 +0000
    Re: Automatic strings without malloc Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-11-17 07:36 -0800
      Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-17 16:56 +0100
        Re: Automatic strings without malloc scott@slp53.sl.home (Scott Lurndal) - 2021-11-17 18:21 +0000
          Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-17 20:37 +0100
            Re: Automatic strings without malloc scott@slp53.sl.home (Scott Lurndal) - 2021-11-17 21:35 +0000
              Re: Automatic strings without malloc Thiago Adams <thiago.adams@gmail.com> - 2021-11-19 05:38 -0800
                Re: Automatic strings without malloc Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-11-19 07:13 -0800
            Re: Automatic strings without malloc William Ahern <william@25thandClement.com> - 2021-11-17 20:46 -0800
              Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-18 10:50 +0100
                Re: Automatic strings without malloc Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-11-18 03:56 -0800
                Re: Automatic strings without malloc Thiago Adams <thiago.adams@gmail.com> - 2021-11-18 05:54 -0800
                Re: Automatic strings without malloc Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-11-18 16:38 +0000
                Re: Automatic strings without malloc Thiago Adams <thiago.adams@gmail.com> - 2021-11-18 10:52 -0800
                Re: Automatic strings without malloc Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-11-18 11:27 -0800
                Re: Automatic strings without malloc Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-11-18 20:41 +0000
                Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-18 16:05 +0100
        Re: Automatic strings without malloc Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-11-17 11:22 -0800
          Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-17 20:39 +0100
            Re: Automatic strings without malloc Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-11-17 15:18 -0800
              [OT] Generally... [Was: Automatic strings without malloc] Jeremy Brubaker <jbrubake@orionarts.invalid> - 2021-11-18 17:46 +0000
                Re: [OT] Generally... [Was: Automatic strings without malloc] Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-11-18 11:21 -0800
  Re: Automatic strings without malloc Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-11-17 11:14 -0800
    Re: Automatic strings without malloc pozz <pozzugno@gmail.com> - 2021-11-18 10:08 +0100
  Re: Automatic strings without malloc Siri Cruise <chine.bleu@yahoo.com> - 2021-11-18 12:25 -0800
    Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-18 23:19 +0100
      Re: Automatic strings without malloc Siri Cruise <chine.bleu@yahoo.com> - 2021-11-18 17:22 -0800
        Re: Automatic strings without malloc Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-11-19 01:46 -0800
          Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-19 17:29 +0100
        Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-19 17:26 +0100
          Re: Automatic strings without malloc Siri Cruise <chine.bleu@yahoo.com> - 2021-11-19 09:00 -0800
            Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-19 18:25 +0100
              Re: Automatic strings without malloc "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-11-19 14:58 -0800
            Re: Automatic strings without malloc Guillaume <message@bottle.org> - 2021-11-19 19:37 +0100
          Re: Automatic strings without malloc "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-11-19 12:34 -0800
            Re: Automatic strings without malloc Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-11-19 13:44 -0800
              Re: Automatic strings without malloc David Brown <david.brown@hesbynett.no> - 2021-11-20 13:30 +0100
                Re: Automatic strings without malloc luser droog <luser.droog@gmail.com> - 2021-11-20 20:49 -0800

csiph-web