[PATCH] utimens: fix confusing arg type in internal func

[Paul Eggert]

Although the old code was technically correct, this was accidental
and it understandably confused Coverity.  Reported by Ondrej Dubaj in:
https://lists.gnu.org/r/bug-tar/2021-04/msg00000.html
* lib/utimens.c (update_timespec): Change arg type from ‘struct
timespec *[2]’ (pointer to array of 2 pointers to timespecs) to
‘struct timespec **’ (pointer to pointer to the first timespec in
an array of 2 timespecs).  Although the old code happened to be
technically correct, it was misleading and confused Coverity.
And though the type ‘struct timespec (**)[2]’ (pointer to pointer
to array of 2 timespecs) would perhaps be more technically
correct, it would be almost as confusing and would require changes
elsewhere in this file; let’s quit while we’re ahead.
---
 ChangeLog     | 14 ++++++++++++++
 lib/utimens.c |  6 +++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 8d8725be2..5d91c7acc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -9,6 +9,20 @@
 
 2021-04-07  Paul Eggert  <eggert@cs.ucla.edu>
 
+       utimens: fix confusing arg type in internal func
+       Although the old code was technically correct, this was accidental
+       and it understandably confused Coverity.  Reported by Ondrej Dubaj in:
+       https://lists.gnu.org/r/bug-tar/2021-04/msg00000.html
+       * lib/utimens.c (update_timespec): Change arg type from ‘struct
+       timespec *[2]’ (pointer to array of 2 pointers to timespecs) to
+       ‘struct timespec **’ (pointer to pointer to the first timespec in
+       an array of 2 timespecs).  Although the old code happened to be
+       technically correct, it was misleading and confused Coverity.
+       And though the type ‘struct timespec (**)[2]’ (pointer to pointer
+       to array of 2 timespecs) would perhaps be more technically
+       correct, it would be almost as confusing and would require changes
+       elsewhere in this file; let’s quit while we’re ahead.
+
        xalloc: simplify integer overflow test
        * lib/xalloc.h (x2nrealloc): Simplify integer overflow detection.
        This is easier to maintain, and (unlike the old code) exact.
diff --git a/lib/utimens.c b/lib/utimens.c
index 44d1ea003..06d1aa36f 100644
--- a/lib/utimens.c
+++ b/lib/utimens.c
@@ -126,14 +126,14 @@ validate_timespec (struct timespec timespec[2])
   return result + (utime_omit_count == 1);
 }
 
-/* Normalize any UTIME_NOW or UTIME_OMIT values in *TS, using stat
-   buffer STATBUF to obtain the current timestamps of the file.  If
+/* Normalize any UTIME_NOW or UTIME_OMIT values in (*TS)[0] and (*TS)[1],
+   using STATBUF to obtain the current timestamps of the file.  If
    both times are UTIME_NOW, set *TS to NULL (as this can avoid some
    permissions issues).  If both times are UTIME_OMIT, return true
    (nothing further beyond the prior collection of STATBUF is
    necessary); otherwise return false.  */
 static bool
-update_timespec (struct stat const *statbuf, struct timespec *ts[2])
+update_timespec (struct stat const *statbuf, struct timespec **ts)
 {
   struct timespec *timespec = *ts;
   if (timespec[0].tv_nsec == UTIME_OMIT
-- 
2.30.2