From: Derek Fawcus <dfawcus+lists-tuhs@employees.org>
To: The Eunuchs Hysterical Society <tuhs@tuhs.org>
Subject: Re: [TUHS] Question about early C behavior.
Date: Fri, 10 Jan 2020 20:55:25 +0000 [thread overview]
Message-ID: <20200110205525.GA1766@clarinet.employees.org> (raw)
In-Reply-To: <CAEoi9W4pONAu4QRKnvQ79pRip5LkqQMq=rXgw4YB5bqYL3XNqQ@mail.gmail.com>
On Fri, Jan 10, 2020 at 02:07:53PM -0500, Dan Cross wrote:
>
> My colleague was particularly surprised that this seemed required: even at
> this early stage, the `extern` keyword was present, so why bother with this
> behavior? Why not, instead, make it a link-time error? Please note that if
> two source files have initializers for these variables, then one gets a
> multiple-definition link error. The 1988 ANSI standard made this an error
> (or at least undefined behavior) but the functionality persists; GCC is
> changing its default to prohibit it (my colleague works on clang).
This behaviour differed between platforms, unix using the common approach,
and some other platforms simplying making it a (non common) symbol in the bss.
Having learnt C in its pre-ANSI form on unix, I then ran in to this behaviour
on DOS C compilers. None of which (that I came across) providing the 'common'
behaviour.
DF
next prev parent reply other threads:[~2020-01-10 20:55 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 19:07 Dan Cross
2020-01-10 20:24 ` Paul Winalski
2020-01-10 20:55 ` Derek Fawcus [this message]
2020-01-10 21:02 ` Warner Losh
2020-01-10 21:05 ` Clem Cole
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