Mail Archives: djgpp/1995/08/21/16:21:26
From: Marc Singer <sapien!elf AT nbn DOT nbn DOT com>
Date: Thu, 17 Aug 1995 18:02:11 -0700 (PDT)
It appears that the mkdir call does not clear errno on success. My
code is creating a new path by starting at the full length trying to
create the directory. On failure, it removes the last path element
and tries again until it succeeds. As soon as it does so, it replaces
the path elements one at a time and creates the path one directory at
a time.
Since it fails once, errno is ENOTDIR. The successful mkdir calls do
not clear this value so errno on exit from my procedure is still
ENOTDIR. I patch my procedure by clearing errno before each call to
mkdir.
I'm porting this code fragment as part of CVS. I notice that the
procedure assumes that mkdir returns ENOENT when the directory cannot
be created. Is the ENOTDIR an incorrect return value? ENOENT is what
the Linux libc returns.
Most library functions only set errno and do not clear it. It is not safe, in
general, to test errno after a function return without first checking the
function's other error indication (like returning -1 or NULL) or without having
cleared errno yourself before calling the library function. Even if you have
recently checked errno and found it clear an intervening function, even one of
your own, may have set it or called another function which set it. I always
test the functions error indication to discover an error and reserve the use of
errno to determine the nature of the error. I have known others, however, whose
convention was to clear errno before any library call and then rely on its
value upon function return; and they even keep their jobs! Whichever.
--
Art S. Kagel, kagel AT ts1 DOT bloomberg DOT com
Variety is the soul of pleasure. -- Aphra Behn
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