[CMake] Forcing linking compatability to old libc / libstdc++ (Linux)

[Florent Castelli]

I've had to deal with this in the past.

For glibc, it's more tricky since when you compile on a newer 
distribution, it will automatically use the newer version of some 
symbols. Some functions have had breaking changes and to keep 
compatibility, they kept all the different version in the binary.
But you can force the compiler to use a specific version of head but 
putting that information in a header that contains the definition for 
all those functions.
There is a script describe in this blog post ( 
https://blogs.gnome.org/tvb/2013/12/14/application-bundles-revisited/ ) 
you could use to generate a compatibility header for any target version 
of glibc.
Then, you can use a force include (-include) in your favorite build 
system (CMake) to have those used everywhere automatically.
If your application doesn't use any external libraries linked statically 
and built against your current glibc, it should work. Otherwise, you 
will probably have to rebuild them.

For libstdc++, you could potentially statically link it, it's usually fine.
But after what I said about glibc, it means you may have to rebuild it 
using the compatibility header described before. That may be tricky too...

/Florent

On 26/01/2017 23:34, Michael Ellery wrote:
>> On Jan 26, 2017, at 1:45 PM, Gonzalo Garramuño <ggarra13 at gmail.com> wrote:
>>
>>
>>
>> El 26/01/2017 a las 18:35, Michael Ellery escribió:
>>> In what way is the stdlib incompatible? Does it have bugs, or is this more a matter of cpp standard support?
>> I should have been more clear.  Sorry.   The incompatabilities happen at linker time, with complaints such as:
>>
>> exrstdattr: /lib64/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by exrstdattr )
>> exrstdattr: /lib64/libstdc++.so.6: version `GLIBCXX_3.4.20' not found (required by /usr/local/mrViewer/lib/libIlmImf-2_2.so.22 )
>>
>> If I copy the latest libstdc++.so.6 I have on Ubuntu, I get:
>>
>> exrstdattr: /lib64/libc.so.6: version `GLIBC_2.18' not found (required by /usr/local/mrViewer/lib/libstdc++.so.6 )
>>
>> -- 
>> Gonzalo Garramuño
>>
> oh, yeah - I wasn’t paying close attention to the fact that you are distributing *binaries* — to a different distro no less. This is why projects often either tell users to build from source or they create packages (rpms, dpkgs, etc.) on the specific distros and versions.
>
> That said, if you want to distribute binaries to a different distro, I guess you can try static linking OR what you suggested, shipping the stdlib — see:
>
> http://stackoverflow.com/questions/13636513/linking-libstdc-statically-any-gotchas#14082540
>
> I personally would not want to ship a stdlib myself, but using CMake’s RPATH support, you can probably make it work.
>
> -Mike
>