* bug#36405: 26.2.90; O_PATH problem on some versions of Cygwin
@ 2019-06-27 19:28 Ken Brown
2019-06-27 20:47 ` Paul Eggert
0 siblings, 1 reply; 9+ messages in thread
From: Ken Brown @ 2019-06-27 19:28 UTC (permalink / raw)
To: 36405
[-- Attachment #1: Type: text/plain, Size: 366 bytes --]
Cygwin supports the O_PATH flag starting with release 3.0.0, but it is buggy
until release 3.0.8. (Opening a FIFO with O_PATH causes a hang.) The attached
patches work around this problem. The first patch (which still has a bug number
that needs to be filled in) uses incorrect indentation for legibility. The
second patch fixes the indentation.
Ken
[-- Attachment #2: 0001-Avoid-O_PATH-on-versions-of-Cygwin-where-it-is-buggy.patch --]
[-- Type: text/plain, Size: 1611 bytes --]
From 8a350e90dc8d047e8372a53dd64fc178157b3f52 Mon Sep 17 00:00:00 2001
From: Ken Brown <kbrown@cornell.edu>
Date: Thu, 27 Jun 2019 14:54:09 -0400
Subject: [PATCH 1/2] Avoid O_PATH on versions of Cygwin where it is buggy
* src/dired.c [O_PATH] (use_o_path): New function.
(file_attributes): Use it. (Bug#99999)
---
src/dired.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/src/dired.c b/src/dired.c
index 493758292b..ac83a026de 100644
--- a/src/dired.c
+++ b/src/dired.c
@@ -36,6 +36,10 @@
#include <filemode.h>
#include <stat-time.h>
+#if defined CYGWIN && defined O_PATH
+#include <sys/utsname.h>
+#endif
+
#include "lisp.h"
#include "systime.h"
#include "buffer.h"
@@ -921,6 +925,21 @@ DEFUN ("file-attributes", Ffile_attributes, Sfile_attributes, 1, 2, 0,
id_format);
}
+/* Cygwin supports O_PATH starting with release 3.0.0, but it is buggy
+ until release 3.0.8. */
+#ifdef O_PATH
+static bool
+use_o_path (void)
+{
+# ifdef CYGWIN
+ struct utsname name;
+ return uname (&name) >= 0 && strverscmp (name.release, "3.0.8") >= 0;
+# else
+ return true;
+# endif
+}
+#endif
+
static Lisp_Object
file_attributes (int fd, char const *name,
Lisp_Object dirname, Lisp_Object filename,
@@ -938,6 +957,8 @@ file_attributes (int fd, char const *name,
int err = EINVAL;
#ifdef O_PATH
+ if (use_o_path ())
+ {
int namefd = openat (fd, name, O_PATH | O_CLOEXEC | O_NOFOLLOW);
if (namefd < 0)
err = errno;
@@ -960,6 +981,7 @@ file_attributes (int fd, char const *name,
name = "";
}
}
+ }
#endif
if (err == EINVAL)
--
2.21.0
[-- Attachment #3: 0002-src-dired.c-file_attributes-Fix-indentation.patch --]
[-- Type: text/plain, Size: 1693 bytes --]
From cd7bbc1e088033789b2948578fc85099ed11a2f1 Mon Sep 17 00:00:00 2001
From: Ken Brown <kbrown@cornell.edu>
Date: Thu, 27 Jun 2019 15:04:05 -0400
Subject: [PATCH 2/2] ; * src/dired.c (file_attributes): Fix indentation
---
src/dired.c | 48 ++++++++++++++++++++++++------------------------
1 file changed, 24 insertions(+), 24 deletions(-)
diff --git a/src/dired.c b/src/dired.c
index ac83a026de..dfec2d89d8 100644
--- a/src/dired.c
+++ b/src/dired.c
@@ -958,30 +958,30 @@ file_attributes (int fd, char const *name,
#ifdef O_PATH
if (use_o_path ())
- {
- int namefd = openat (fd, name, O_PATH | O_CLOEXEC | O_NOFOLLOW);
- if (namefd < 0)
- err = errno;
- else
- {
- record_unwind_protect_int (close_file_unwind, namefd);
- if (fstat (namefd, &s) != 0)
- {
- err = errno;
- /* The Linux kernel before version 3.6 does not support
- fstat on O_PATH file descriptors. Handle this error like
- missing support for O_PATH. */
- if (err == EBADF)
- err = EINVAL;
- }
- else
- {
- err = 0;
- fd = namefd;
- name = "";
- }
- }
- }
+ {
+ int namefd = openat (fd, name, O_PATH | O_CLOEXEC | O_NOFOLLOW);
+ if (namefd < 0)
+ err = errno;
+ else
+ {
+ record_unwind_protect_int (close_file_unwind, namefd);
+ if (fstat (namefd, &s) != 0)
+ {
+ err = errno;
+ /* The Linux kernel before version 3.6 does not support
+ fstat on O_PATH file descriptors. Handle this error like
+ missing support for O_PATH. */
+ if (err == EBADF)
+ err = EINVAL;
+ }
+ else
+ {
+ err = 0;
+ fd = namefd;
+ name = "";
+ }
+ }
+ }
#endif
if (err == EINVAL)
--
2.21.0
^ permalink raw reply related [flat|nested] 9+ messages in thread* bug#36405: 26.2.90; O_PATH problem on some versions of Cygwin
2019-06-27 19:28 bug#36405: 26.2.90; O_PATH problem on some versions of Cygwin Ken Brown
@ 2019-06-27 20:47 ` Paul Eggert
2019-06-28 6:25 ` Eli Zaretskii
2019-06-28 17:57 ` Ken Brown
0 siblings, 2 replies; 9+ messages in thread
From: Paul Eggert @ 2019-06-27 20:47 UTC (permalink / raw)
To: Ken Brown; +Cc: 36405-done
[-- Attachment #1: Type: text/plain, Size: 276 bytes --]
Thanks, but that patch intrudes on the mainline code a bit. It's simpler
to just disable O_PATH on Cygwin until the old Cygwin versions die out.
Also, there's a similar issue in fileio.c. I installed the attached,
which should work around the problem in both source files.
[-- Attachment #2: 0001-Work-around-Cygwin-bug-with-O_PATH.patch --]
[-- Type: text/x-patch, Size: 1105 bytes --]
From e7200b3cf9b4a6470197915a31c45739f078683b Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Thu, 27 Jun 2019 13:05:05 -0700
Subject: [PATCH] Work around Cygwin bug with O_PATH
Problem reported by Ken Brown (Bug#36405).
* src/dired.c, src/fileio.c (O_PATH) [__CYGWIN__]: Undef.
---
src/dired.c | 4 ++++
src/fileio.c | 4 ++++
2 files changed, 8 insertions(+)
diff --git a/src/dired.c b/src/dired.c
index 493758292b..b8197d36a0 100644
--- a/src/dired.c
+++ b/src/dired.c
@@ -41,6 +41,10 @@
#include "buffer.h"
#include "coding.h"
+#ifdef __CYGWIN__
+# undef O_PATH /* Buggy in Cygwin 3.0.0 through 3.0.7. */
+#endif
+
#ifdef MSDOS
#include "msdos.h" /* for fstatat */
#endif
diff --git a/src/fileio.c b/src/fileio.c
index ed1d2aedf3..e36118652c 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -61,6 +61,10 @@ Copyright (C) 1985-1988, 1993-2019 Free Software Foundation, Inc.
# include <linux/fs.h>
#endif
+#ifdef __CYGWIN__
+# undef O_PATH /* Buggy in Cygwin 3.0.0 through 3.0.7. */
+#endif
+
#ifdef WINDOWSNT
#define NOMINMAX 1
#include <windows.h>
--
2.21.0
^ permalink raw reply related [flat|nested] 9+ messages in thread
* bug#36405: 26.2.90; O_PATH problem on some versions of Cygwin
2019-06-27 20:47 ` Paul Eggert
@ 2019-06-28 6:25 ` Eli Zaretskii
2019-06-29 6:26 ` Paul Eggert
2019-06-28 17:57 ` Ken Brown
1 sibling, 1 reply; 9+ messages in thread
From: Eli Zaretskii @ 2019-06-28 6:25 UTC (permalink / raw)
To: Paul Eggert; +Cc: 36405, eggert
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Thu, 27 Jun 2019 13:47:27 -0700
> Cc: 36405-done@debbugs.gnu.org
>
> Thanks, but that patch intrudes on the mainline code a bit. It's simpler
> to just disable O_PATH on Cygwin until the old Cygwin versions die out.
IMO, that's too drastic. Cygwin 3 is quite new, AFAIK, so it will be
years and years before the old versions die out; no one will remember
this bit by then.
What problems did you see/envision on other platforms with the
original patch?
^ permalink raw reply [flat|nested] 9+ messages in thread
* bug#36405: 26.2.90; O_PATH problem on some versions of Cygwin
2019-06-28 6:25 ` Eli Zaretskii
@ 2019-06-29 6:26 ` Paul Eggert
2019-06-29 7:06 ` Eli Zaretskii
0 siblings, 1 reply; 9+ messages in thread
From: Paul Eggert @ 2019-06-29 6:26 UTC (permalink / raw)
To: Eli Zaretskii; +Cc: 36405
[-- Attachment #1: Type: text/plain, Size: 634 bytes --]
Eli Zaretskii wrote:
> What problems did you see/envision on other platforms with the
> original patch?
Mainly the hassle of maintaining code with a lot of hard-to-read ifdefs in it.
It's better if system-specific stuff is kept to a minimum in mainline code.
Also, this O_PATH stuff is not that high of a priority, as the code works quite
well in practice without O_PATH. (Also, if Cygwin botched O_PATH on FIFOs
there's a reasonable chance it botched O_PATH elsewhere too. :-)
How about something like the attached patch instead? It's simpler and should be
a bit faster on Cygwin than the original patch. I haven't tested it.
[-- Attachment #2: cygwin.diff --]
[-- Type: text/x-patch, Size: 1023 bytes --]
diff --git a/configure.ac b/configure.ac
index 8ff0e21fbf..a0e99ac393 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5734,6 +5734,9 @@ AC_DEFUN
AC_MSG_WARN([[building Emacs on Cygwin 1.5 is not supported.]])
echo
;;
+ cygwin,3.0.[0-8]'('*)
+ AC_DEFINE([HAVE_CYGWIN_O_PATH_BUG], 1,
+ [Define to 1 if opening a FIFO with O_PATH causes a hang.]);;
esac
# Remove any trailing slashes in these variables.
diff --git a/src/dired.c b/src/dired.c
index b8197d36a0..b700013f6a 100644
--- a/src/dired.c
+++ b/src/dired.c
@@ -41,10 +41,6 @@
#include "buffer.h"
#include "coding.h"
-#ifdef __CYGWIN__
-# undef O_PATH /* Buggy in Cygwin 3.0.0 through 3.0.7. */
-#endif
-
#ifdef MSDOS
#include "msdos.h" /* for fstatat */
#endif
@@ -941,7 +937,7 @@ file_attributes (int fd, char const *name,
int err = EINVAL;
-#ifdef O_PATH
+#if defined O_PATH && !defined HAVE_CYGWIN_O_PATH_BUG
int namefd = openat (fd, name, O_PATH | O_CLOEXEC | O_NOFOLLOW);
if (namefd < 0)
err = errno;
^ permalink raw reply related [flat|nested] 9+ messages in thread* bug#36405: 26.2.90; O_PATH problem on some versions of Cygwin
2019-06-29 6:26 ` Paul Eggert
@ 2019-06-29 7:06 ` Eli Zaretskii
2019-06-29 18:03 ` Ken Brown
0 siblings, 1 reply; 9+ messages in thread
From: Eli Zaretskii @ 2019-06-29 7:06 UTC (permalink / raw)
To: Paul Eggert; +Cc: 36405
> Cc: 36405@debbugs.gnu.org, kbrown@cornell.edu
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Fri, 28 Jun 2019 23:26:09 -0700
>
> Eli Zaretskii wrote:
> > What problems did you see/envision on other platforms with the
> > original patch?
>
> Mainly the hassle of maintaining code with a lot of hard-to-read ifdefs in it.
> It's better if system-specific stuff is kept to a minimum in mainline code.
I agree, of course. But in this case we are talking about adding 2
#ifdef's, so the situation is not much worse than it was before.
> Also, this O_PATH stuff is not that high of a priority, as the code works quite
> well in practice without O_PATH.
It was evidently important enough for us to use it on platforms that
support it.
> How about something like the attached patch instead? It's simpler and should be
> a bit faster on Cygwin than the original patch. I haven't tested it.
Thanks, this is fine with me if it does the job. Ken?
^ permalink raw reply [flat|nested] 9+ messages in thread
* bug#36405: 26.2.90; O_PATH problem on some versions of Cygwin
2019-06-29 7:06 ` Eli Zaretskii
@ 2019-06-29 18:03 ` Ken Brown
2019-06-29 18:19 ` Eli Zaretskii
0 siblings, 1 reply; 9+ messages in thread
From: Ken Brown @ 2019-06-29 18:03 UTC (permalink / raw)
To: Eli Zaretskii, Paul Eggert; +Cc: 36405@debbugs.gnu.org
[-- Attachment #1: Type: text/plain, Size: 1137 bytes --]
On 6/29/2019 3:06 AM, Eli Zaretskii wrote:
>> Cc: 36405@debbugs.gnu.org, kbrown@cornell.edu
>> From: Paul Eggert <eggert@cs.ucla.edu>
>> Date: Fri, 28 Jun 2019 23:26:09 -0700
>>
>> Eli Zaretskii wrote:
>>> What problems did you see/envision on other platforms with the
>>> original patch?
>>
>> Mainly the hassle of maintaining code with a lot of hard-to-read ifdefs in it.
>> It's better if system-specific stuff is kept to a minimum in mainline code.
>
> I agree, of course. But in this case we are talking about adding 2
> #ifdef's, so the situation is not much worse than it was before.
>
>> Also, this O_PATH stuff is not that high of a priority, as the code works quite
>> well in practice without O_PATH.
>
> It was evidently important enough for us to use it on platforms that
> support it.
>
>> How about something like the attached patch instead? It's simpler and should be
>> a bit faster on Cygwin than the original patch. I haven't tested it.
>
> Thanks, this is fine with me if it does the job. Ken?
Fine with me too, after a small tweak. Revised patch attached.
Thanks, Paul.
Ken
[-- Attachment #2: cygwin1.diff --]
[-- Type: text/plain, Size: 1025 bytes --]
diff --git a/configure.ac b/configure.ac
index 8ff0e21fbf..774f8e5eb9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5734,6 +5734,9 @@ AC_DEFUN
AC_MSG_WARN([[building Emacs on Cygwin 1.5 is not supported.]])
echo
;;
+ cygwin,3.0.[[0-7]]'('*)
+ AC_DEFINE([HAVE_CYGWIN_O_PATH_BUG], 1,
+ [Define to 1 if opening a FIFO with O_PATH causes a hang.]);;
esac
# Remove any trailing slashes in these variables.
diff --git a/src/dired.c b/src/dired.c
index b8197d36a0..b700013f6a 100644
--- a/src/dired.c
+++ b/src/dired.c
@@ -41,10 +41,6 @@
#include "buffer.h"
#include "coding.h"
-#ifdef __CYGWIN__
-# undef O_PATH /* Buggy in Cygwin 3.0.0 through 3.0.7. */
-#endif
-
#ifdef MSDOS
#include "msdos.h" /* for fstatat */
#endif
@@ -941,7 +937,7 @@ file_attributes (int fd, char const *name,
int err = EINVAL;
-#ifdef O_PATH
+#if defined O_PATH && !defined HAVE_CYGWIN_O_PATH_BUG
int namefd = openat (fd, name, O_PATH | O_CLOEXEC | O_NOFOLLOW);
if (namefd < 0)
err = errno;
^ permalink raw reply related [flat|nested] 9+ messages in thread* bug#36405: 26.2.90; O_PATH problem on some versions of Cygwin
2019-06-29 18:03 ` Ken Brown
@ 2019-06-29 18:19 ` Eli Zaretskii
0 siblings, 0 replies; 9+ messages in thread
From: Eli Zaretskii @ 2019-06-29 18:19 UTC (permalink / raw)
To: Ken Brown; +Cc: eggert, 36405
> From: Ken Brown <kbrown@cornell.edu>
> CC: "36405@debbugs.gnu.org" <36405@debbugs.gnu.org>
> Date: Sat, 29 Jun 2019 18:03:02 +0000
>
> > Thanks, this is fine with me if it does the job. Ken?
>
> Fine with me too, after a small tweak. Revised patch attached.
Go ahead and push, then.
Thanks.
^ permalink raw reply [flat|nested] 9+ messages in thread
* bug#36405: 26.2.90; O_PATH problem on some versions of Cygwin
2019-06-27 20:47 ` Paul Eggert
2019-06-28 6:25 ` Eli Zaretskii
@ 2019-06-28 17:57 ` Ken Brown
2019-06-29 6:20 ` Paul Eggert
1 sibling, 1 reply; 9+ messages in thread
From: Ken Brown @ 2019-06-28 17:57 UTC (permalink / raw)
To: Paul Eggert; +Cc: 36405@debbugs.gnu.org
On 6/27/2019 4:47 PM, Paul Eggert wrote:
> --- a/src/fileio.c
> +++ b/src/fileio.c
> @@ -61,6 +61,10 @@ Copyright (C) 1985-1988, 1993-2019 Free Software Foundation, Inc.
> # include <linux/fs.h>
> #endif
>
> +#ifdef __CYGWIN__
> +# undef O_PATH /* Buggy in Cygwin 3.0.0 through 3.0.7. */
> +#endif
This hunk is not necessary. The only use of O_PATH in fileio.c is coupled with
O_DIRECTORY, and this is not affected by the bug.
But, in any case, I agree with Eli's point that your patch is too drastic. I
don't see how my patch is intrusive.
Ken
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2019-06-29 18:19 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2019-06-27 19:28 bug#36405: 26.2.90; O_PATH problem on some versions of Cygwin Ken Brown
2019-06-27 20:47 ` Paul Eggert
2019-06-28 6:25 ` Eli Zaretskii
2019-06-29 6:26 ` Paul Eggert
2019-06-29 7:06 ` Eli Zaretskii
2019-06-29 18:03 ` Ken Brown
2019-06-29 18:19 ` Eli Zaretskii
2019-06-28 17:57 ` Ken Brown
2019-06-29 6:20 ` Paul Eggert
Code repositories for project(s) associated with this external index
https://git.savannah.gnu.org/cgit/emacs.git
https://git.savannah.gnu.org/cgit/emacs/org-mode.git
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.