[cmake-developers] New no-soname-option topic for e.g. Android

[Nils Gladitz]

On 28.05.2014 20:15, Brad King wrote:
> On 05/28/2014 12:17 PM, Nils Gladitz wrote:
>> In case you drop "-Wl,-soname" entirely ... how do you work around the
>> issue of the linker using paths rather than names in NEEDED entries?
>> Or does the issue not exist on OpenBSD?
> This is an important issue.
>
> CMake generates link command lines that refer to library files by path
> rather than asking the linker to search with a -lfoo option.  This
> approach ensures the expected library file is linked.  If the library
> file has no DT_SONAME then some linkers put the path in DT_NEEDED.
> For example, compare three commands for linking to a /path/to/libfoo.so
> file that has no DT_SONAME:
>
>   ====================================  ==============================
>   Command Line                          Result
>   ====================================  ==============================
>   cc A.c -o A -L/path/to -lfoo          DT_NEEDED = libfoo.so
>   cc B.c -o B /path/to/libfoo.so        DT_NEEDED = /path/to/libfoo.so
>   cd /path && cc C.c -o C to/libfoo.so  DT_NEEDED = to/libfoo.so
>   ====================================  ==============================
>
> Therefore linking by path to a library requires that the library
> have a DT_SONAME, or that the linker be modified to do something
> else for DT_NEEDED.
>
> -Brad
>

I was curious and did a VM install of OpenBSD (5.5) to have a peek.
Most of this will be obvious to OpenBSD users but this was all rather 
new to me :p ...

There is a /usr/lib/libz.so.5.0
There is no /usr/lib/libz.so
-lz links to /usr/lib/libz.so.5.0 nonetheless
The library has no SONAME.
None of the libraries under /usr/lib in the default install seem to have 
an SONAME though I am able to create libraries with SONAME manually.

The linker does embed paths to libraries in NEEDED entries like it would 
on e.g. GNU/Linux.

This seems to imply that convention on OpenBSD is indeed to not have any 
SONAMEs at all.

Given that the topic might have one valid use case after all?

Nils