maint: handle file sizes more reliably

Problem reported by Samuel Thibault in <http://bugs.gnu.org/11424>.
* NEWS: Document this.
* src/dd.c (skip): Handle skipping past EOF on shared or typed
memory objects the same way as with regular files.
(dd_copy): It's OK to truncate shared memory objects.
* src/du.c (duinfo_add): Check for overflow.
(print_only_size): Report overflow.
(process_file): Ignore negative file sizes in the --apparent-size case.
* src/od.c (skip): Fix comment about st_size.
* src/split.c (main):
* src/truncate.c (do_ftruncate, main):
On files where st_size is not portable, fall back on using lseek
with SEEK_END to determine the size.  Although strictly speaking
POSIX says the behavior is implementation-defined, in practice
if lseek returns a nonnegative value it's a reasonable one to
use for the file size.
* src/system.h (usable_st_size): Symlinks have reliable st_size too.
* tests/misc/truncate-dir-fail: Don't assume that getting the size
of a dir is not allowed, as it's now allowed on many platforms,
e.g., GNU/Linux.

1 files changed, 0 insertions, 3 deletions

diff --git a/tests/misc/truncate-dir-fail b/tests/misc/truncate-dir-fail
index 116735208..54a31479f 100755
--- a/tests/misc/truncate-dir-fail
+++ b/tests/misc/truncate-dir-fail
@@ -22,7 +22,4 @@ print_ver_ truncate
 # truncate on dir not allowed
 truncate -s+0 . && fail=1
 
-# getting the size of a dir is not allowed
-truncate -r. file && fail=1
-
 Exit $fail