Sujet : Re: do { quit; } else { }
De : david.brown (at) *nospam* hesbynett.no (David Brown)
Groupes : comp.lang.cDate : 10. Apr 2025, 13:46:00
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <vt8ei8$2vn84$1@dont-email.me>
References : 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
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On 10/04/2025 10:55, Michael S wrote:
On Wed, 09 Apr 2025 14:44:39 -0700
Keith Thompson <Keith.S.Thompson+u@gmail.com> wrote:
Michael S <already5chosen@yahoo.com> writes:
On Wed, 9 Apr 2025 12:58:08 +0200
Janis Papanagnou <janis_papanagnou+ng@hotmail.com> wrote:
On 09.04.2025 11:42, David Brown wrote:
On 08/04/2025 18:28, bart wrote:
[...]
>
I believe the meaning of "extern" in combination with other
storage-class specifiers was picked to work with existing old
code from before "extern" was added to the language.
>
Assuming you mean the "C" language I don't quite understand the
last part of the sentence. Wasn't 'extern' already in "K&R" - so
what was "the language" before the addition of 'extern'?
>
Or did you just mean to say "[...] before _combinations_ of
'extern' and other storage-class specifier were added to the
language."
>
Janis, puzzled
>
K&R was published in 1978, 5 years after C got its first users.
Back in 1973-74 C language was significantly different from what it
became few years later.
>
The earliest C reference I have is cman74.pdf, currently at
<http://cm.bell-labs.co/who/dmr/cman74.pdf>. It includes "extern" in
the list of keywords.
>
It was inherited from B, which had "extrn" as a keyword as of 1972.
>
O.k. Then David Brown will have to look for different justification for
this particular misfeature of great majority of Unix implementations of
C language.
There have been a variety of things under discussion here, but I think this particular one was about the linkage rules in C if an identifier is declared with "static int foo;" and/or "extern int foo;" and/or "int foo;" at file scope, possibly in different orders. My thought was that one influence on the rules was consistency of existing code after "extern" was added to the language, but it seems unlikely since no one knows of an early C without "extern".
So currently, I have no explanation for why you may write "static int foo; extern int foo;" and have "foo" be internal linkage, while "extern int foo; static int foo;" is not allowed. Given that neither are likely to be of the remotest use, nor likely to be written by accident and go unnoticed, it should not affect anyone significantly.
But if someone else has an explanation for this, or a realistic use-case for static followed by extern, I am curious to hear about it.
do { quit; } else { }
Re: do { quit; } else { }