[CMake] Finding 32bit libs on 64bit Ubuntu install

[Nick Deubert]

On Mon, Apr 25, 2016 at 4:01 PM, Alan W. Irwin
<irwin at beluga.phys.uvic.ca> wrote:
> On 2016-04-25 14:06-0400 Nick Deubert wrote:
>
>> On Fri, Apr 22, 2016 at 5:08 PM, Alan W. Irwin
>> <irwin at beluga.phys.uvic.ca> wrote:
>>>
>>> On 2016-04-22 14:59-0400 Nick Deubert wrote:
>>>
>>>> Hey everyone, I am trying to build and link some 32bit binaries on
>>>> Ubuntu 15.10 64bit, but no matter what combination of arguments I give
>>>> FIND_LIBRARY I cannot get it to use the 32bit libs. I have been
>>>> scouring the mailing lists and came up with all these things to try
>>>> but nothing has worked so far. I am using cmake 3.0.2. Please let me
>>>> know what I am missing. Thanks in advance for your help.
>>>
>>>
>>>
>>> CMake 3.0.2 is pretty old, and there were some find and other issues
>>> for early CMake-3 versions.  I don't know whether any of those issues
>>> are relevant to the issue you are discussing. Nevertheless, as an
>>> experiment (and to make sure your eventual solution works for the
>>> latest CMake) I would suggest you try building and using the latest
>>> released version of CMake, 3.5.2, to see if that makes any difference.
>>>
>>> Alan
>>
>>
>> Ok I upgraded to 3.2.2 which is the latest ubuntu 15.10 offers (I will
>> try 16.04 w/3.5.1 soon), but I get the same issue.
>
>
>> Is my syntax all correct as far as you can tell?
>
>
> Hi Nick:
>
> The syntax is OK _as far as I can tell_, but I did notice one important
> issue in the libdl information you supplied with your original post which is
> your 64-bit version of libdl is
>
> -- DL_LIBRARY is /usr/lib/x86_64-linux-gnu/libdl.so
>
> but there is no libdl.so in your 32-bit directory listings.  The closest
> you come is
>
> /lib/i386-linux-gnu/libdl.so.2 -> libdl-2.21.so
>
> but that doesn't cut it, and you need a development symlink (provided
> by the development version of a library package) that defines a 32-bit
> libdl.so symlink that can be found by CMake. Such symlink would
> ordinarily be supplied by a Ubuntu development package.  I don't have
> Ubuntu installed myself, but Ubuntu is based on Debian, and for Debian
> jessie the package name is libc6-dev-i386, and it contains the
>
> /usr/lib32/libdl.so
>
> symlink.  So look for a similarly named package for Ubuntu, verify it
> contains
> libdl.so  (I did that on Debian using "apt-file search libdl.so") and
> install it.

Solved! I did have the 32bit-dev libraries installed but your tip made
me realize the plain .so files are installed into
/usr/lib/i386-linux-gnu and not /lib/i386-linux-gnu. As soon as I
switched to that path it is finding all the right libs. I didn't
realize cmake wouldn't parse the version numbers, so that is a very
good thing to know.
Thanks for your help!
Nick