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References: <22038 DOT 29093 DOT 221000 DOT 863384 AT woitok DOT gmail DOT com>	<CAJygYd3DLkzj=Va7uuU8-NSjUG6kog0YqBuvhDMMA=0vZwY+=Q AT mail DOT gmail DOT com>
Date: Thu, 8 Oct 2015 16:54:48 +0200
Message-ID: <CAEhDDbBze5TQCQe+wp7AZgww19TOC7DYv3ZBRy7hxPj1Uv5d9w@mail.gmail.com>
Subject: Re: Running a program using a DLL under Cygwin
From: Csaba Raduly <rcsaba AT gmail DOT com>
To: cygwin list <cygwin AT cygwin DOT com>
Cc: Rainer DOT Woitok AT gmail DOT com
Content-Type: text/plain; charset=UTF-8

Hi,

On Thu, Oct 8, 2015 at 3:56 PM, Yucong Sun  wrote:

Please don't top-post (https://cygwin.com/acronyms/#TOFU)

> I think symlink is a cygwin thing.  Windows won't find that DLL (just
> like you won't find it using windows explorer.)
>
> Windows only support loading DLL from project directory, or  system32
> as far as I know.

There are rather more possibilities, listed here:
https://msdn.microsoft.com/en-us/library/windows/desktop/ms682586%28v=vs.85%29.aspx

1. The directory from which the application loaded.
2. The current directory.
3. The system directory. Use the GetSystemDirectory function to get
the path of this directory.
4. The 16-bit system directory. There is no function that obtains the
path of this directory, but it is searched.
5. The Windows directory. Use the GetWindowsDirectory function to get
the path of this directory.
6. The directories that are listed in the PATH environment variable.
Note that this does not include the per-application path specified by
the App Paths registry key. The App Paths key is not used when
computing the DLL search path.

If SafeDllSearchMode is enabled, the current directory is demoted from
#2 to #5 (just before the PATH search).

There's also SetDllDirectory (
https://msdn.microsoft.com/en-us/library/windows/desktop/ms686203%28v=vs.85%29.aspx
)

>
> On Thu, Oct 8, 2015 at 9:37 PM, Dr Rainer Woitok
> <rainer DOT woitok AT gmail DOT com> wrote:
>> Greetings,
>>
>> I'm running  a program which requires a DLL  sitting in my "~/bin/" dir-
>> ectory.  Since "~/bin/" is contained  in my "PATH" environment variable,
>> everything works  as desired.   Recently I moved  the DLL elsewhere, re-
>> placing it with a symbolic link in "~/bin/".  This caused the program to
>> fail to locate the DLL.  Moving the DLL back in place caused the program
>> to work again.
>>
>> Is this a Windows problem  (since DLLs are Windows  rather than Unix) or
>> Cygwin's?   The link was created with the normal  "ln -s" command.  And,
>> if that matters, Cygwin is running on Vista here.

If the CYGWIN environment contains    winsymlinks:native
(https://cygwin.com/cygwin-ug-net/using.html#pathnames-symlinks) ,
Cygwin creates symlinks that Windows can understand. I don't know
whether Windows will load a DLL if a native symlink to the DLL is in
the PATH (or any other directories in the search list).

Csaba
-- 
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