[Info-vax] Possible C compiler static variable initialization problem.

[johnwallace4 at yahoo.co.uk]

On Wednesday, 26 February 2014 18:40:54 UTC, Simon Clubley  wrote:
> On 2014-02-26, Simon Clubley <clubley at remove_me.eisner.decus.org-Earth.UFP> wrote:
> 
> > On 2014-02-26, Bob Koehler <koehler at eisner.nospam.encompasserve.org> wrote:
> 
> >> In article <leko68$egf$1 at dont-email.me>, Simon Clubley <clubley at remove_me.eisner.decus.org-Earth.UFP> writes:
> 
> >>> 
> 
> >>> On VMS, variables defined in different source files, but with the same name,
> 
> >>> were traditionally treated as different variables by the linker and space
> 
> >>> allocated for each variable definition.
> 
> >>
> 
> >>    I've been working with C on VMS since early VAX C days, and I've
> 
> >>    never seen that.   A file level variable (outside of any function)
> 
> >>    is treats as global to the code unless it's specificially declared
> 
> >>    static.
> 
> >>
> 
> >
> 
> > My apologies for the wrong information than.
> 
> >
> 
> > I encountered this back in the 90s with a C compiler and I had thought it
> 
> > was on VMS. I wonder if it was one of the early Microsoft C MS-DOS/Win 9x
> 
> > compilers which I worked with in that timeframe as well ?
> 
> >
> 
> 
> 
> I'm now really curious about this now I think I've remembered a bit more.
> 
> IIRC, on the C compiler in question you only had one declaration allowed
> 
> for a variable at file level and all the other file level declarations
> 
> in other source files _had_ to be extern references to the first
> 
> declaration.
> 
> 
> 
> After thinking about it a bit more, I cannot be sure anymore, if you tried
> 
> to define the variable twice at file level in different source files, if
> 
> the linker wrongly allocated additional space for the second variable
> 
> (like I stated above) or if it issued a multiple allocation error.
> 
> 
> 
> Anyone ever worked with a compiler like this and remember the compiler
> 
> and operating system ?
> 
> 
> 
> Thanks,
> 
> 
> 
> Simon.
> 
> 
> 
> PS: I've just tried it on Linux and binutils merged the two definitions
> 
> for "unsigned long int a;" in different source files together without
> 
> error just as expected and my test program treated them as one variable.
> 
> 
> 
> -- 
> 
> Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
> 
> Microsoft: Bringing you 1980s technology to a 21st century world

Did you ever have the pleasure of working with Whitesmiths C?

I did, on RSX/IAS and (unofficially) on RT11. It had a number of
non-intuitive features, and I have a vague recollection that the
handling of "extern" (?) vars, with respect to defining and referencing
instances, might have been one of them. Or something like that,
something maybe not a million miles from your recollection.

PSECT attributes (OVR/CON? [NO]SHR?) also come into this, in some
circumstances.

Some info on potentially relevant Compaq C behaviours:
http://h71000.www7.hp.com/commercial/c/docs/5492p018.html