11 Jan
2020
11 Jan
'20
3:02 a.m.
On Fri, Jan 10, 2020, 1:55 PM Derek Fawcus <dfawcus+lists-tuhs(a)employees.org wrote:
On Fri, Jan 10, 2020 at 02:07:53PM -0500, Dan Cross
wrote:
Gcc offered warnings for this behavior in the early 90s, iirc. I went
through a bunch of code in that time frame to remove the assumption...
Warner
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.