[CMake] Undefined reference

[Michael Hertling]

On 11/03/2011 06:39 PM, Mauricio Klein wrote:
> ldd reports that is not dynamically executable, as expected. But even ldd
> saying that, the problem with GLIBC occurs.

What exactly does ldd report, and how exactly the executable is linked?

Regards,

Michael

> On Thu, Nov 3, 2011 at 3:33 PM, Michael Hertling <mhertling at online.de>wrote:
> 
>> On 11/03/2011 06:20 PM, Mauricio Klein wrote:
>>> The error reported occurs in the launch time: the daemon doesn't starts
>> and
>>> report (in terminal) a GLIBC version error. [...]
>>
>> Usually, this means that it has *not* been linked statically against
>> the GLIBC on the build system. Which dependencies does ldd report?
>>
>>> [...] I mean, the daemon was compiled
>>> in a old CentOS (4.8) and i'm trying to run in the latest Ubuntu.
>>>
>>> But anyway, i will make more tests as you sugested and try to discovery
>>> what exactly is happening.
>>>
>>> Once again, thank you so much for your help!
>>>
>>> On Thu, Nov 3, 2011 at 3:09 PM, Michael Hertling <mhertling at online.de
>>> wrote:
>>>
>>>> On 11/03/2011 03:51 PM, Mauricio Klein wrote:
>>>>> Thank you Raphael, it worked!
>>>>>
>>>>> One last question: i've tried to compile my code using static linkage,
>>>> once
>>>>> i need my daemon runs in many Linux releases. But, even static, in many
>>>>> systems my code crashes because the GLIBC version.
>>>>
>>>> How do these crashes manifest themselves, e.g. shell/syslog messages,
>>>> return values, core dumps etc.? Are you sure they are related to the
>>>> GLIBC version? Does the executable actually have no single dependency
>>>> on any shared library, i.e. is it linked statically in its entirety?
>>>> What does ldd or readelf report?
>>>>
>>>>> My question is: asking for static linkage in CMake can solve this
>>>> problem?
>>>>
>>>> If even a statically linked executable crashes on the target system,
>>>> telling CMake to link statically will hardly solve this problem. ;)
>>>>
>>>>> Or maybe another approach in CMake, where i embed all the needed
>>>>> libraries...
>>>>
>>>> You might take a look the the BundleUtilities Module, but at first,
>>>> I'd recommend to investigate what exactly causes the crashes. Your
>>>> best bet is probably to provide a tiny but self-contained example
>>>> that works on your development platform and crashes on a target
>>>> system, along with some information about the latter's setup.
>>>>
>>>> Regards,
>>>>
>>>> Michael
>>>>
>>>>> On Thu, Nov 3, 2011 at 12:19 PM, Raphael Kubo da Costa
>>>>> <rakuco at freebsd.org>wrote:
>>>>>
>>>>>> Mauricio Klein
>>>>>> <mauricio.klein.msk at gmail.com> writes:
>>>>>>
>>>>>>> I can compile all my codes without problems, but in the linkage
>> step, i
>>>>>>> receive a lot of errors about undefined reference to OpenSSL
>> functions
>>>>>>> (yes, my code uses OpenSSL).
>>>>>>>
>>>>>>> In my own (and ugly :P) Makefile, i use "-lssl" flag in g++ compile
>>>> line.
>>>>>>>
>>>>>>> My question is: how can i pass this flag in CMake.
>>>>>>> Also, i'm not sure if i'm using CMake correctly. Is correctly use
>>>> "-lssl"
>>>>>>> flag in CMake or i need to copy the library to a folder inside my
>>>> project
>>>>>>> and link to this copy?
>>>>>>
>>>>>> You need to find OpenSSL with `find_package(OpenSSL)' and then,
>> assuming
>>>>>> it is found (ie. OPENSSL_FOUND is true), link to its libraries with
>>>>>> `target_link_libraries(YOUR_APP ${OPENSSL_LIBRARIES})'.