Re: [PATCH 1/2] xopen: explicitly report creation failures

René Scharfe [off-list ref] writes:

Am 26.08.21 um 01:46 schrieb Carlo Arenas:

quoted

On Wed, Aug 25, 2021 at 2:11 PM René Scharfe [off-list ref] wrote:

quoted

diff --git a/wrapper.c b/wrapper.c
index 563ad590df..7c6586af32 100644
--- a/wrapper.c
+++ b/wrapper.c

@@ -193,7 +193,9 @@ int xopen(const char *path, int oflag, ...)
                if (errno == EINTR)
                        continue;

-               if ((oflag & O_RDWR) == O_RDWR)
+               if ((oflag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
+                       die_errno(_("unable to create '%s'"), path);

probably over conservative, but && errno == EEXIST?

No matter what error we got, if O_CREAT and O_EXCL were both given then
we tried to create a file, so this message applies.

100% agreed.

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+               else if ((oflag & O_RDWR) == O_RDWR)
                        die_errno(_("could not open '%s' for reading and writing"), path);
                else if ((oflag & O_WRONLY) == O_WRONLY)
                        die_errno(_("could not open '%s' for writing"), path);

Since you are already changing this code, why not take the opportunity
to refactor it
and remove the " == FLAG" part of these conditionals which is
otherwise redundant?

The repetition is unsightly, but it's a different issue that should be
addressed separately.  Simply removing the comparison feels iffy,
though.  POSIX doesn't seem to forbid e.g. O_RDONLY to be 1, O_WRONLY
to be 2 and O_RDWR to be 3, and then you need to check all masked bits.
I can't think of simpler alternative to the comparison.

I fully agree that such a change, if done, must be done in an
unrelated patch.  

It is funny that the code is already prepared for such a case where
RDWR is defined as RDONLY|WRONLY.  I wonder if we wrote the series
of comparisons in this order on purpose, or we were just lucky, when
we did 3ff53df7 (wrapper: implement xopen(), 2015-08-04) ;-)

quoted

Either way "Reviewed-by", and indeed a nice cleanup.

Thank you!

Yes, indeed, this is nicely done.