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Re: [PATCH 1/6] fix ambiguous errno treating after mktime()
My 2c: preserving errno is not a desirable goal. Portable code
can't rely on it being preserved, people need to learn that,
and it's awkward to implement in some situations even when it
Robert -- I have a query about your postscript:
Robert Elz <kre%munnari.OZ.AU@localhost> wrote:
> ps: it is actually quite hard to preserve errno, as it isn't
> guaranteed to be an Lvalue, ...
Um, is that so? Has there been a standard that doesn't
require errno to be an lvalue, or implementations where it
isn't or wasn't?
Looking at "The Single Unix Specification, Version 2":
Previously both POSIX and X/Open documents were more
restrictive than the ISO C standard in that they required
errno to be defined as an external variable, whereas the
ISO C standard required only that errno be defined as a
modifiable lvalue with type int.
A program that uses errno for error checking should set it
to 0 before a function call, then inspect it before a
subsequent function call.
I read that to mean (and have always believed) that whatever
funky type errno is implemented as, it is required to be an
lvalue. Unfortunately I don't have a copy of the ISO C
standard to hand to check what it says for C99.
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