Hi,
(sorry for sending a little bit late) Note that since changeset:mainline,
2397 there is a change to how I/O functions return error. If you are working
on a project that works with files, you may be affected.
Before the change, the 'native' I/O functions (open(), read(), write(),close
(), etc.) returned >=0 on success (in some cases a meaningful value, such as
fd, number of records transferred). On failure they would return negative
error code. After this change, on error they return -1 and set errno.
This means any code that actually distinguishes between different error
codes will be impacted. What's worse, if your code uses file functions, it
will still compile, it just won't handle the errors properly. There is no
easy way to check for this, except to audit all uses of file functions (I
did this in mainline).
The main motivation for this change: I consider functions that return >=0 on
success and negative error code on error bad interface design because the
return value mixes two unrelated things. It makes code checking the error
value sensitive to the sign of Exxx constants. (As you know these are
negative in HelenOS and positive in UNIX). The file functions in HelenOS are
named like the UNIX functions, they have *almost* the same signatures and
they behave *almost* the same. This led to a lot of cases where the caller
errorneously assumed the functions behave like their UNIX counterparts (e.g.
in Bdsh - since it was ported from Linux).
While nothing precludes HelenOS having a file API completely distict from
the UNIX-like one (which should have nonconflicting function names), in this
case the easiest immediate fix was to just align the functions with the UNIX
-like ones.
Please let me know if you have any questions or concerns or if you need help
with updating your code.
Best regards,
Jiri
(http://trac.helenos.org/changeset/mainline%2C2397)
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