Re: Checking failing dlopen when building 32bit software

[Bob Friesenhahn]

On Mon, 11 Oct 2021, alexandre schenberg wrote:
>   which made sense, as I had not yet made a symbolic link to libdl on
>   /usr/lib32. Then I just did it. Yet, this error message continued to
>   appear. What changed was this detection test: "checking for dlopen in
>   -ldl..." that went from "no" to "yes", notwithstanding  that "checking
>   for dlopen." continued to return no.
>
>   Following suggestion on a message board, I was able to circumvent these
>   "skipping incompatible" error messages  by adding a "-L/usr/lib32/
>   -ldl" to the end of wine's configure parameter list.

Adding -L/usr/lib32/ was likely the correct thing to do.

>   So what was left from these messages on wine, mesa and alsa was the:
>   "checking for dlopen... no". It did not stop me to build Alsa. I don't
>   know about mesa and wine, since I still have many other tests to deal
>   it before I can try to compile them. What I am afraid of, is that this
>   can make a software to refuse to run for not finding the 32bit library
>   that it requires (like wine not finding a .so alsa library)

If the software does not use dlopen, then support for dynamic modules 
or dynamically loading libraries may be missing from it.  Depending on 
the software, this might severely diminish its functionality.

>   Does this fear have any basis or am I looking for trouble without need?
>   Can I safely ignore this libdl check?
>
>   I also would like to understand the reason behind the "skipping
>   incompatible" error messages. It seems it was looking for libdl on
>   /usr/lib64/ instead /usr/lib32. If so, why? I understand that
>   /usr/lib32 did not exist when the system was installed, but looking for
>   a 32bit library on a 64bit dir just does not compute.

I suggest reading the documentation for 'ldconfig' and 'ld.so'.

The "skipping incompatible" message is really a warning but it becomes 
significant if the 32-bit library is not found.

Major x86-64 Linux distributions appear to be in the process of 
removing 32-bit support.  Be aware that if you get 32-bit support 
working today on your Linux distribution that it might not work in the 
next major release cycle.

Bob
--
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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