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Groups > comp.lang.c > #401424

Re: Question about struct initializers

From David Brown <david.brown@hesbynett.no>
Newsgroups comp.lang.c
Subject Re: Question about struct initializers
Date 2026-08-22 13:29 +0200
Organization A noiseless patient Spider
Message-ID <116c176$1274o$2@dont-email.me> (permalink)
References (3 earlier) <1166ost$3dg4d$1@dont-email.me> <1166psa$375be$1@news.xmission.com> <1167kdh$3oo4a$2@dont-email.me> <1168uba$2168$4@dont-email.me> <116a8ek$ishu$1@dont-email.me>

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On 21/08/2026 21:20, Chris M. Thomasson wrote:
> On 8/21/2026 12:22 AM, David Brown wrote:
>> On 20/08/2026 21:26, Chris M. Thomasson wrote:
>>> On 8/20/2026 4:53 AM, Kenny McCormack wrote:
>>>> In article <1166ost$3dg4d$1@dont-email.me>,
>>>> David Brown  <david.brown@hesbynett.no> wrote:
>>>> ...
>>>>> (It's nice to see that your reputation as group cynic has not been
>>>>> totally ruined by your clear, topical C question starting this 
>>>>> thread!)
>>>>
>>>> Heh heh.  Well, somebody's got to do it.
>>>>
>>>> This actually came up in real code that I was working on, and it 
>>>> seemed odd
>>>> that it worked (*).  Unless it was actually part of the language, as 
>>>> it now
>>>> seems it is.
>>>>
>>>> (*) Worked in the sense that it was always 0.  Not that the code was
>>>> relying on that, of course.
>>>>
>>>
>>> simply never assume that a in say:
>>>
>>> int a;
>>>
>>> equals zero. Its fairly simple.
>>
>> That only applies to non-static local variables.  Program lifetime 
>> data is always initialised.  Code can happily rely on initialisation 
>> happening as required by the rules of the C language.
>>
> 
> Shit. Well, still, I have a habit of trying to initialize everything. 
> So, yes, I tend to write:
> 
> static int g_a = 0;

Write that if you like - and if it makes code clearer, it can be a good 
thing.  It is unlikely to be helpful to the reader to have an explicit 
"0" initialiser, but it certainly could be if it is an enumeration 
value, constexpr value, macro, or something else that is not obviously 0.

Contrary to Lawrence's answer, it typically /will/ make a difference to 
generated code - just one that is completely negligible in all but the 
smallest of embedded systems.  In most of the toolchains I have used, 
"static int g;" goes in the ".bss" segment and gets zeroed as part of a 
loop, while "static int g = 0;" goes in the ".data" segment and is 
initialised by copying from a read-only segment of the executable.  Thus 
the explicit initialisation is marginally less efficient.

On the other hand, there are a few embedded toolchains (primarily those 
provided by Texas Instruments) which do not zero-initialise program 
lifetime data that has no explicit initialisation - they do not clear 
the ".bss" and "static int g;" variables before main().  The misguided 
fools at TI call this a "feature" leading to faster startup - users call 
it a painful and deceptive flaw and non-conformity which has lead to 
countless problems and wasted debugging time.  It has also lead some 
providers of portable embedded code to use explicit initialisation to 0 
as you have done, giving less efficient code on platforms with more 
conforming tools.

> 
> Shit happens.

I get the impression that you don't understand what that phrase means. 
You should stop using it - it makes no sense in the contexts you write it.

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Thread

Question about struct initializers gazelle@shell.xmission.com (Kenny McCormack) - 2026-08-17 20:48 +0000
  Re: Question about struct initializers bart <bc@freeuk.com> - 2026-08-17 22:21 +0100
    Re: Question about struct initializers Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-18 06:46 +0800
  Re: Question about struct initializers bixbox <noreply@example.invalid> - 2026-08-17 23:23 +0200
    Re: Question about struct initializers Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-18 06:47 +0800
    Re: Question about struct initializers David Brown <david.brown@hesbynett.no> - 2026-08-18 10:39 +0200
  Re: Question about struct initializers scott@slp53.sl.home (Scott Lurndal) - 2026-08-17 21:44 +0000
    Re: Question about struct initializers Michael S <already5chosen@yahoo.com> - 2026-08-18 01:06 +0300
      Re: Question about struct initializers David Brown <david.brown@hesbynett.no> - 2026-08-18 11:11 +0200
        Re: Question about struct initializers Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-18 03:58 -0700
    Re: Question about struct initializers richard@cogsci.ed.ac.uk (Richard Tobin) - 2026-08-17 22:34 +0000
      Re: Question about struct initializers Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-18 06:39 +0800
        Re: Question about struct initializers richard@cogsci.ed.ac.uk (Richard Tobin) - 2026-08-17 23:03 +0000
          Re: Question about struct initializers Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-18 11:24 +0800
          Re: Question about struct initializers David Brown <david.brown@hesbynett.no> - 2026-08-18 11:19 +0200
      Re: Question about struct initializers David Brown <david.brown@hesbynett.no> - 2026-08-18 11:16 +0200
      Re: Question about struct initializers Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-18 22:45 +0000
        Re: Question about struct initializers richard@cogsci.ed.ac.uk (Richard Tobin) - 2026-08-19 00:08 +0000
          Re: Question about struct initializers Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-19 04:32 +0000
            Re: Question about struct initializers Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-18 22:34 -0700
            Re: Question about struct initializers richard@cogsci.ed.ac.uk (Richard Tobin) - 2026-08-19 12:21 +0000
              Re: Question about struct initializers David Brown <david.brown@hesbynett.no> - 2026-08-19 14:33 +0200
                Re: Question about struct initializers scott@slp53.sl.home (Scott Lurndal) - 2026-08-19 14:53 +0000
              Re: Question about struct initializers Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-19 23:29 +0000
                Re: Question about struct initializers Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-19 17:43 -0700
                Re: Question about struct initializers richard@cogsci.ed.ac.uk (Richard Tobin) - 2026-08-20 09:56 +0000
                Re: Question about struct initializers scott@slp53.sl.home (Scott Lurndal) - 2026-08-20 14:53 +0000
                Re: Question about struct initializers Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-20 13:34 -0700
                Re: Question about struct initializers scott@slp53.sl.home (Scott Lurndal) - 2026-08-20 21:00 +0000
                Re: Question about struct initializers tTh <tth@none.invalid> - 2026-08-21 05:43 +0200
                Re: Question about struct initializers scott@slp53.sl.home (Scott Lurndal) - 2026-08-21 14:56 +0000
                Re: Question about struct initializers Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-22 00:31 +0800
              Re: Question about struct initializers gazelle@shell.xmission.com (Kenny McCormack) - 2026-08-20 02:00 +0000
                Why are you picking on Lawrence? (was: Re: Question about struct initializers) Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-20 13:16 +0800
                Re: Why are you picking on Lawrence? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-20 12:24 -0700
                Re: Question about struct initializers richard@cogsci.ed.ac.uk (Richard Tobin) - 2026-08-20 10:14 +0000
                Re: Question about struct initializers gazelle@shell.xmission.com (Kenny McCormack) - 2026-08-20 11:54 +0000
                Re: Question about struct initializers David Brown <david.brown@hesbynett.no> - 2026-08-20 13:37 +0200
                Re: Question about struct initializers gazelle@shell.xmission.com (Kenny McCormack) - 2026-08-20 11:53 +0000
                Re: Question about struct initializers David Brown <david.brown@hesbynett.no> - 2026-08-20 14:42 +0200
                Re: Question about struct initializers "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-20 12:26 -0700
                Re: Question about struct initializers David Brown <david.brown@hesbynett.no> - 2026-08-21 09:22 +0200
                Compiler bugs (was: Re: Question about struct initializers) Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-22 00:26 +0800
                Re: Question about struct initializers "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-21 12:20 -0700
                Re: Question about struct initializers Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-22 05:55 +0000
                Re: Question about struct initializers David Brown <david.brown@hesbynett.no> - 2026-08-22 13:29 +0200
                Re: Question about struct initializers "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-22 14:16 -0700
                Re: Question about struct initializers "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-22 14:17 -0700
                Re: Question about struct initializers Michael S <already5chosen@yahoo.com> - 2026-08-23 01:23 +0300
            Re: Question about struct initializers "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-19 12:25 -0700
              Re: Question about struct initializers Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-20 04:07 +0800
                Re: Question about struct initializers "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-19 13:17 -0700
                Re: Question about struct initializers Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-20 04:27 +0800
                Re: Question about struct initializers "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-20 12:21 -0700
                Fuck you, and fuck you too (was: Re: Question about struct initializers) Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-21 12:51 +0800
              Re: Question about struct initializers Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-20 04:10 +0800
        Re: Question about struct initializers Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-18 17:13 -0700
    Re: Question about struct initializers Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-18 06:45 +0800
  Re: Question about struct initializers Michael S <already5chosen@yahoo.com> - 2026-08-18 01:02 +0300
    Re: Question about struct initializers Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-18 06:35 +0800
  Re: Question about struct initializers Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-18 06:32 +0800

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