[CMake] cmake -E create_symlink for Windows

[Bill Lorensen]

http://en.wikipedia.org/wiki/Symbolic_link#Cygwin_symbolic_links

On Mon, Dec 14, 2009 at 3:28 AM, Marcel Loose <loose at astron.nl> wrote:
> On Sat, 2009-12-12 at 12:02 -0500, Bill Hoffman wrote:
>> Alan W. Irwin wrote:
>> > On 2009-12-12 09:44-0500 David Cole wrote:
>> >
>> >> On Fri, Dec 11, 2009 at 10:04 AM, Michael Wild <themiwi at gmail.com> wrote:
>> >>
>> >> Bummer. What where they THINKING??? (if at all...). It seems to me
>> >> that M$ just CAN'T get it right. No matter how many times they try,
>> >> how many good examples are out there, they always manage to seriously
>> >> screw something up... Come to think of it, they probably were thinking
>> >> about symlink-attacks...
>> >>
>> >>
>> >> Come on. Let's make a deal: you don't bash Microsoft, Apple or Google
>> >> here
>> >> on the CMake mailing list and I won't bash Unix or Linux in any forum,
>> >> anywhere, ever. OK? Does that sound cool?
>> >
>> > Absolutely.  There used to be another poster here (before he got
>> > so-over-the-top that he was removed) that kept making gratuitous attacks on
>> > Linux and free software, and that was extremely annoying.  So as a Linux
>> > developer I support Dave's call to be aware of other's strong feelings
>> > and stay on topic so we don't waste a lot of time here.
>> >
>> > Back on topic....
>> >
>> > I am one of the lead developers of the PLplot CMake-based build system.
>> > However, my development experience is Linux only so I must rely on my
>> > Windows developer colleagues to catch any Linux-only or Unix-only
>> > mistakes I
>> > put into our build system.  Up to this thread, I had no idea that there
>> > wasn't some reliable way to create symlinks on Windows, and it's only by
>> > chance that I haven't used create_symlink in any part of our build other
>> > than the Linux-only documentation build.
>> >
>> > Before this thread, I always assumed cmake -E commands gave you an
>> > excellent
>> > way to do common tasks in a cross-platform way.  I appeal to the CMake
>> > developers to avoid from now on implementing any more CMake -E commands
>> > that
>> > have no hope of ever fulfilling that mandate, Also, please deprecate and
>> > document the cmake -E commands with obvious cross-platform limitations
>> > because otherwise your users are going to assume (like I did) that those
>> > commands are the recommended way to help make their project cross-platform.
>> > Is create_symlink an isolated case, or are there other cmake -E commands to
>> > worry about?
>> >
>> > Also, is create_symlink really a lost cross-platform cause?  Reading later
>> > in Dave's post, it appears that the symlink concept does work on some
>> > Windows platform (he mentioned something about "shortcuts").  If there are
>> > intentions to make it work on a number of Windows platforms eventually, but
>> > that just hasn't happened yet, then _warn_ about that issue (e.g.,
>> > something
>> > like "Unix-only for now" in the documentation).  Also, if the CMake -E
>> > command is run on a platform that doesn't support it something better
>> > than a
>> > silent failure should be the result.
>> >
>>
>> Some things just can not be done cross platform.   For example reading/
>> writing the windows registry, creating an OSX application bundle, and
>> sym-links.  Also, some computers don't even have shared libraries.
>> Should we disable those features from CMake?  That said, the symlink
>> command is the only -E that does not work cross platform.   The -E
>> create_symlink does return failure from main when called on windows.
>> So, if you used it in a custom command which is the idea for -E stuff,
>> it would fail in a noticeable way (the build would fail).  If you call
>> it from execute_process, you should be checking the return value as well.
>>
>> -Bill
>
> Just out of curiosity: how does Cygwin handle this whole symbolic link
> business?
>
> Marcel Loose.
>
>
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