windows bug: filewritable() returns 0 if we use it on the current script being read
Philippe Vaucher
I think I've found a bug for vim under windows.
Basically if inside a vim script you do
"filewritable(expand('<sfile>'))" it returns 0 even if the file is
writable.
I read the source and basically it boils down to that the dwShareMode
param of CreateFile() is 0, when it should be FILE_SHARE_READ|
FILE_SHARE_WRITE:
hFile = CreateFileW(wn, am, 0, NULL, OPEN_EXISTING, 0, NULL);
I'm not sure of the implications, but basically I think just changing
the dwShareMode param to the correct value everywhere CreateFile() is
used should fix it. Not that in certain places it's used with the
correct flag value.
Philippe
Philippe Vaucher
Bram Moolenaar
Philippe Vaucher wrote:
It makes sense, but we must make sure this does not cause any trouble.
Does it work on all Windows versions?
On Unix we never care about others having the file open, thus I don't
see a reason to check for that on MS-Windows.
--
Q: How do you tell the difference between a female cat and a male cat?
A: You ask it a question and if HE answers, it's a male but, if SHE
answers, it's a female.
/// Bram Moolenaar -- Br...@Moolenaar.net -- http://www.Moolenaar.net \\\
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Ben Fritz
On Nov 2, 7:21 am, Philippe Vaucher <philippe.vauc...@gmail.com>
wrote:
while you are executing its contents as a script. It sounds like this
is what is happening. Is there some reason you want to write the file
while executing it?
Philippe Vaucher
> Does it work on all Windows versions?
if your question is if CreateFile()'s dwShareMode flag is supported on
all flavors of windows I think the answer is yes. Based on
http://msdn.microsoft.com/en-us/library/aa363874(v=VS.85).aspx and on
http://msdn.microsoft.com/en-us/library/aa363858(VS.85).aspx it looks
like CreateFile goes back to windows 2000.
I'm pretty new to digging into vim's source so I don't know if windows
98 is supported (I was also a bit surprised by the old-style function
declarations :).
Anyway, I guess I could simply build vim and check if the problem goes
away if I add the relevant flag everywhere CreateFile is used, but how
do I make sure it didn't break other stuffs? My instincts tell me this
should not create any problem as you'd normally not care about any
file being already opened or not, but maybe I'm wrong, and I'm not
sure about what I should test to assert at least the basic stuffs work
as expected beside opening some files and checking my vim still
works :)
> On Unix we never care about others having the file open, thus I don't
> see a reason to check for that on MS-Windows.
the current windows behavior differs in that respect.
Thanks,
Philippe
Philippe Vaucher
> while you are executing its contents as a script. It sounds like this
> is what is happening. Is there some reason you want to write the file
> while executing it?
in order to decide to go and write to the parent directory or go to
alternate routes like ~/.vim etc. If you want more details I'll be
happy to provide them but the point is that if such behavior is
enabled in *nix it'd also be enabled in windows or disabled in both.
The thing I'm really after is consistency, the fix for the particular
script was to change it to check the script's directory instead which
works consistently on both platforms.
Philippe
Craig Barkhouse
Changing the share mode to (FILE_SHARE_READ | FILE_SHARE_WRITE) in mch_access() is theoretically safe, because mch_access() doesn't do any I/O and closes the handle immediately. It would not be ok to make a broader change throughout the source code to always open handles with more permissive sharing. When you use those share modes, basically you're saying "I'm opening a file handle now, and I really don't care if anyone else is reading and/or writing the file at the same time as I'm working with the file." In general you do care. If you're writing to a file, you don't want another process also writing, which would result in undefined file contents. You don't really want one process reading while another process is writing either, because then the reader will see an inconsistent view. The only type of sharing that is typically safe is read-read.
Assuming you don't want permissive sharing when doing actual I/O (I argue above that you don't), I question the value of changing mch_access() in the proposed way. The point of mch_access() is to give you a predictor of what types of access will likely work. If the access check tells you that opening the file for write will work, but then when you actually open it for write (using realistic sharing values) it fails, isn't this worse than what we have now?
The proposed change to mch_access() would only address a narrow scenario anyway. It allows you to avoid a sharing violation imposed by *your* handle. You'll still see sharing violations imposed by *other* handles. The general rule is that the access mode of any opened handle must be compatible with the share mode of all other opened handles.
Craig
John Beckett
> Assuming you don't want permissive sharing when doing actual
> I/O (I argue above that you don't), I question the value of
> changing mch_access() in the proposed way. The point of
> mch_access() is to give you a predictor of what types of
> access will likely work. If the access check tells you that
> opening the file for write will work, but then when you
> actually open it for write (using realistic sharing values)
> it fails, isn't this worse than what we have now?
Although I haven't followed exactly what the OP is proposing,
what Craig says is correct. Allowing multiple writers to the
same file is only desirable under very planned circumstances
which do NOT include a text editor writing to a file.
John
Philippe Vaucher
means the "bug" is in the current *nix version. IMHO vim should behave
as consistently as possible on the platforms it runs on, thus we'd
then change the *nix api to behave like the current win32 one.
Also, the way vim behaves on win32 about this is probably
inconsistent, as a test script I did the following:
echo 'writable: ' . filewritable(expand('<sfile>'))
write!
When I do ":source %" it output writable: 0, then writes the file
anyway :)
So I *think* that originally the vim authors never intended to prevent
other processes/whatever from begin able to open the same files, only
that on windows on some occasions the authors got lazy and forgot
about the dwSharedMode flag and just set it to 0. Someone should
decide wether we want to prevent it or not and then implement it on
all the platforms.
Philippe
Philippe Vaucher
a file? Should we allow writers on currently read file? If no how
drastics are the changes to be made to the linux api?
Philippe
Roland Puntaier
After installing vim7.3 on a ubuntu system, I had again the problem that
import did not work for .so libraries in lib-dynload. I found that
sys.path was initialized with "/usr/..." instead of "/usr/local/...". On
ubuntu (and probably on other linux distros as well) python3 is
installed in /usr/local while python2 is installed in /usr.
The attached patch calls Py_SetPythonHome with PYTHON3_PREFIX defined by
configure.
This solves the problem.
regards, Roland
James Vega
> Hi Bram,
>
> After installing vim7.3 on a ubuntu system, I had again the problem
> that import did not work for .so libraries in lib-dynload. I found
> that sys.path was initialized with "/usr/..." instead of
> "/usr/local/...". On ubuntu (and probably on other linux distros as
> well) python3 is installed in /usr/local while python2 is installed
> in /usr.
That's not the case at all[0]. No distribution package should install
to /usr/local as that's a reserved directory structure for the system
administrator[1]. If your Python3 install is in /usr/local, then whoever
admins that system installed it there.
> The attached patch calls Py_SetPythonHome with PYTHON3_PREFIX
> defined by configure.
> This solves the problem.
This does make sense for supporting people who have installed Python
outside of the standard paths, though. This should probably be done for
Python2.x as well.
[0]: http://packages.ubuntu.com/maverick/i386/python3.1/filelist
[1]: http://www.pathname.com/fhs/pub/fhs-2.3.html#USRLOCALLOCALHIERARCHY
--
James
GPG Key: 1024D/61326D40 2003-09-02 James Vega <jame...@jamessan.com>
James Vega
> On Sun, Nov 07, 2010 at 06:04:35PM +0200, Roland Puntaier wrote:
> > The attached patch calls Py_SetPythonHome with PYTHON3_PREFIX
> > defined by configure.
> > This solves the problem.
>
> This does make sense for supporting people who have installed Python
> outside of the standard paths, though. This should probably be done for
> Python2.x as well.
Would it make more sense to use Py_GetPrefix() or Py_GetExecPrefix() as the
input to Py_SetPythonHome() instead?
Philippe Vaucher
managed to change the subject.
Look at http://groups.google.com/group/vim_dev/browse_thread/thread/6972ae8d369cf671/a183f61488f3006c#
Philippe
Roland Puntaier
>
> Why the hell happened there? Seems you replied to the wrong thread and
> managed to change the subject.
>
> Look at http://groups.google.com/group/vim_dev/browse_thread/thread/6972ae8d369cf671/a183f61488f3006c#
>
> Philippe
>
>
Using Thunderbird I've chosen an arbitrary message from vim_dev and
changed subject and body.
I didn't know that the threading is done on invisible email message
fields other than the subject. I looked at the email source and found
fields like References and In-Reply-To.
There is always something new to learn. For my next message I'll take it
into account.
Roland Puntaier
> On Sun, Nov 07, 2010 at 06:04:35PM +0200, Roland Puntaier wrote:
>
>> Hi Bram,
>>
>> After installing vim7.3 on a ubuntu system, I had again the problem
>> that import did not work for .so libraries in lib-dynload. I found
>> that sys.path was initialized with "/usr/..." instead of
>> "/usr/local/...". On ubuntu (and probably on other linux distros as
>> well) python3 is installed in /usr/local while python2 is installed
>> in /usr.
>>
>
> That's not the case at all[0]. No distribution package should install
> to /usr/local as that's a reserved directory structure for the system
> administrator[1]. If your Python3 install is in /usr/local, then whoever
> admins that system installed it there.
>
python 3.x defaults to /usr/local prefix. And anyway, for the problem,
it doesn't matter how it got there.
>> The attached patch calls Py_SetPythonHome with PYTHON3_PREFIX
>> defined by configure.
>> This solves the problem.
>>
>
>