On 11/15/21 19:14, Sudhip Nashi wrote:
lseek(0x3, 0x0, 0x3) = -1 Err#6
Oh my, it appears lseek (fd, 0, SEEK_HOLE) is failing with errno ==
ENXIO when the file has no holes, even though the Darwin man page
clearly states that lseek should return the file size in that case (see
<https://github.com/apple/darwin-xnu/blob/main/bsd/man/man2/lseek.2>).
So, not only does macOS lseek disagree with all other implementations,
it even disagrees with the Darwin documentation.
To work around this macOS problem I installed the attached further patch
into Gnulib and propagated it into coreutils. Please try the latest
coreutils version on Savannah, or you can simply run configure+make from
the tarball that is temporarily at:
https://web.cs.ucla.edu/~eggert/coreutils-9.0.28-6d0f0.tar.gz
From 1a268176fbb184e393c98575e61fe692264c7d91 Mon Sep 17 00:00:00 2001
From: Paul Eggert <egg...@cs.ucla.edu>
Date: Mon, 15 Nov 2021 22:17:44 -0800
Subject: [PATCH] lseek: port around macOS SEEK_HOLE glitch
Problem reported by Sudhip Nashi (Bug#51857#47).
* lib/lseek.c (rpl_lseek): Work around macOS lseek+SEEK_HOLE
returning -1 with ENXIO if there are no holes before EOF,
contrary to the macOS documentation.
---
ChangeLog | 6 ++++++
lib/lseek.c | 6 ++++--
2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 71a226570..efc3a3887 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
2021-11-15 Paul Eggert <egg...@cs.ucla.edu>
+ lseek: port around macOS SEEK_HOLE glitch
+ Problem reported by Sudhip Nashi (Bug#51857#47).
+ * lib/lseek.c (rpl_lseek): Work around macOS lseek+SEEK_HOLE
+ returning -1 with ENXIO if there are no holes before EOF,
+ contrary to the macOS documentation.
+
lseek: port around macOS SEEK_DATA glitch
Problem reported by Sudhip Nashi (Bug#51857).
* doc/posix-functions/lseek.texi (lseek): Mention macOS SEEK_DATA
diff --git a/lib/lseek.c b/lib/lseek.c
index 7dcd6c9da..e9a96ad20 100644
--- a/lib/lseek.c
+++ b/lib/lseek.c
@@ -61,10 +61,12 @@ rpl_lseek (int fd, off_t offset, int whence)
data followed by a possibly-empty hole. To work around this
portability glitch, check whether OFFSET is within data by
using lseek+SEEK_HOLE, and if so return to OFFSET by using
- lseek+SEEK_SET. */
+ lseek+SEEK_SET. Also, contrary to the macOS documentation,
+ lseek+SEEK_HOLE can fail with ENXIO if there are no holes on
+ or after OFFSET. What a mess! */
off_t next_hole = lseek (fd, offset, SEEK_HOLE);
if (next_hole < 0)
- return next_hole;
+ return errno == ENXIO ? offset : next_hole;
if (next_hole != offset)
whence = SEEK_SET;
}
--
2.32.0
