Re: [MACTCL] Mach-O ID of Tcl 8.7a3 Library

[Marc C. <mar...@gm...>]

Hi Kevan,

Mach-O .dylib files can be used either as shared libraries or as link
libraries.  The LC_ID_DYLIB path is used *only* when you are linking an
executable against the Tcl library, so as to make the executable use the
Tcl library as a shared library.  In that case the executable will acquire
an LC_LOAD_DYLIB path which is the same as the LC_ID_DYLIB path in the Tcl
library.  To change the LC_ID_DYLIB path with install_name_tool you should
use the -id option.  The path that you provide as the value for that option
will become the LC_ID_DYLIB path.  But the otool -L command does *not*
display the LC_ID_DYLIB path of a Mach file.  It displays the LC_LOAD_DYLIB
paths.  And probably the LC_ID_DYLIB path is not your  problem.

You probably linked the main executable of your app against the Tcl library
and you want it to dynamically load the Tcl library.  So what you need to
do is to change (or add) an LC_LOAD_DYLIB path in the main executable of
your app so that it will do that.  The LC_LOAD_DYLIB path that you want
will probably look like
@executable_path/../Frameworks/Tcl.framework/Versions/Current/Tcl.  To do
that with install_name_tool you need to use the -change option, not the -id
option.

I find it a pain to use otool and install_name_tool and that is why I wrote
the utility "macher" which is much more to my taste and can do some things
which are required by Tcl and Tk (now that they support zipfs
singe-file-executables) and which are not available from Apple's tools.
You can download macher from https://github.com/culler/macher/releases .

- Marc

On Sun, Apr 11, 2021 at 10:31 PM Kevan Hashemi <ha...@br...> wrote:

> Greetings,
>
> I compiled the TclTk 8.7a3 embedded Wish shell on MacOS 10.12 (still
> working on getting it to compile on my 10.15 machine). I am delighted with
> its performance. I did encounter one obstacle. In the tcl.framework
> directory we have:
>
> kevan@KSH5 8.7 % otool -L Tcl
> Tcl:
>         /Library/Frameworks/Tcl.framework/Versions/8.7/Tcl (compatibility
> version 8.7.0, current version 8.7.0)
> <snip>
>
> This first line is the Mach-O LC_ID_DYLIB path. Compare to the same path
> for an earlier version of TclTk:
>
> kevan@KSH5 8.6 % otool -L Tcl
> Tcl:
>         @executable_path/../Frameworks/Tcl.framework/Versions/8.6/Tcl
> (compatibility version 8.6.0, current version 8.6.10)
> <snip>
>
> Suppose our embedded Wish shell loads a dynamic library X.dylib. In order
> for X.dylib to install commands into the Tcl interpreter, it must have
> previously been compiled and linked to the Tcl framework. When Wish loads
> X.dylib with the "load" command, it tries to make sure that all libraries
> that X.dylib depends upon are also loaded. So Wish will look for the
> dependent Tcl library in the LC_ID_DYLIB path provided by the Tcl library
> when X.dylib was created. In the case of Tcl 8.7, LC_ID_DYLIB points to a
> non-existent library. In the case of 8.6, LC_ID_DYLIB provids a relative
> path that locates the same Tcl library used by the Wish shell itself.
>
> I have been unable to change LC_ID_DYLIB in the Tcl library with
> install_name_tool, but we can change the path to the Tcl library that is
> recorded in X.dylib, like this:
>
> install_name_tool -change \
>    /Library/Frameworks/Tcl.framework/Versions/8.7/Tcl \
>    @executable_path/../Frameworks/Tcl.framework/Versions/8.7/Tcl \
>    X.dylib
>
> Now Wish can load X.dylib. Meanwhile, the Tk 8.7 library does not have
> this problem: it provides the traditional relative path for LD_ID_DYLIB.
>
> So, I have a fix, which I have automated in my Makefile, but I'm wondering
> if this is something that should be set right in the configure script.
>
> Best, Kevan
>
> --
> Kevan Hashemi, Electrical Engineer
> Physics Department, Brandeis University
> http://www.bndhep.net
>
>
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