🚀 go-pugleaf

In article <4aokt2$14j@elf.bsdi.com>, torek@elf.bsdi.com (Chris Torek) writes:
|>
|>Unfortunately, it is possible, and maybe even ever-so-slightly
|>sensible, for `errno' to refer to a *different* object on return
|>from longjmp.  For instance, suppose a compiler elects to put an
|>`errno' in each activation record (function call stack frame) and
|>to define `errno' as `the current frame's errno', e.g.,
|>
|>	#define errno (__builtin_upframe(0)->__errno)
|>
|>C library functions that set errno would use a different define,
|>such as:
|>
|>	#define callers_errno (__builtin_upframe(1)->__errno)

I hate to question anything Chris Torek says, because it's almost guaranteed
to make me look stupid, but here goes:

If there's a different errno for each activation record, then what happens if
function A calls function B, function B calls a system function during which
an error occurs, function B returns an error indication to function A, and
function A attempts to look at errno (A's own errno, not B's errno) to see
what happened?

--

Chris Volpe				Phone: (518) 387-7766 (Dial Comm 8*833
GE Corporate R&D			Fax:   (518) 387-6560
PO Box 8, Schenectady, NY 12301		Email: volpecr@crd.ge.com