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Re: Question about struct initializers

From David Brown <david.brown@hesbynett.no>
Newsgroups comp.lang.c
Subject Re: Question about struct initializers
Date 2026-08-20 13:37 +0200
Organization A noiseless patient Spider
Message-ID <1166ost$3dg4d$1@dont-email.me> (permalink)
References <115vs2l$2rp49$1@news.xmission.com> <1162s6m$gkbk$1@artemis.inf.ed.ac.uk> <1163bl5$2c1o2$1@dont-email.me> <116473r$hal8$1@artemis.inf.ed.ac.uk> <1165n3p$3589c$1@news.xmission.com>

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On 20/08/2026 04:00, Kenny McCormack wrote:
> In article <116473r$hal8$1@artemis.inf.ed.ac.uk>,
> Richard Tobin <richard@cogsci.ed.ac.uk> wrote:
> ...
>> In the early days of C, this was often so, and some programs
>> wrongly depended on it.  In some of those cases the mistake became
>> apparent when shared libraries were introduced, because of the dynamic
>> linker running before main().
> 
> It would have been clearer (although it was certainly clear enough for
> anyone with a triple digit IQ, but LDO seems not to have reached that
> level) if this had been explained in terms of the introduction of the
> dynamic linker running before main() is called - rather than in terms of
> the introduction of shared libs. Using the term "shared libraries" as a
> proxy for "the dynamic linker" begat the possibility of confusion on the
> part of careless readers.
> 
> And besides, it seems to me that even without either "shared libraries" or
> a "dynamic linker", it has always been the case that non-main() code runs
> before main is called.  C is usually implemented as a bit of startup code
> (often stored in crt0.lib or some such) that does stuff, then does a "call"
> of "main".  So that startup code could easily corrupt the (formerly
> pristine) "stack".

That's certainly possible.  As well as any dynamic linker stuff, there 
can be constructors run pre-main.  Even if your own code is pure C, 
maybe there are static libraries linked in that were written in C++ or 
other languages, or which made use of gcc's 
"__attribute__((constructor))".  A C standard library could also run 
code for things like sorting out stdin/stdout, setting up a heap, or 
anything else it fancies before calling main().  And some embedded 
toolchains may do even more odd things before main() is called.

Other systems may consistently deliver main() a zeroed stack as 
guaranteed behaviour.

> 
> Note, incidentally, that "the s word" must always be enclosed in scare
> quotes in this newsgroup.
> 

I think it is okay to drop the scare quotation marks when we are talking 
explicitly about stacks.  I have used C on a microcontroller without a 
stack (without any ram at all, in fact), but I think your example code 
would be too big to fit in the code flash.  C systems can be assumed to 
use a stack unless the code also has to work on the DS9000.

(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!)

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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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