[CMake] Link order (Ubuntu)

[Bo Zhou]

Oh, if that's shared libraries, maybe you have to setup the LD_LIBRARY_PATH
well for the shared libraries before linking, it just allows the linker to
be able to locate the all necessary dynamic libraries during the linking.
It happens sometimes on Linux, but not exists on OSX and Windows.

On Tue, Nov 6, 2018 at 11:19 PM Giorgio Scorzelli <scrgiorgio at gmail.com>
wrote:

> Thanks for you help.
>
> They are really shared lib, not static. I know it sounds weird: it's a
> python extension which must not link the ${PYTHON_LIBRARY}  (according to
> official docs; in fact If I do so I get a segmentation fault) but finally
> in my executable,a sort of custom/home made  ${PYTHON_EXECUTABLE}, I have
> to link the ${PYTHON_LIBRARY}.
>
> About the "B;A;ImportedExtLib;B;A" order. I agree too: it SHOULD work.
> Let's say I do:
>
> target_link_libraries(MyExe B A ImpLib)
>
> in command line (make VERBOSE=1) I;m getting
>
> g++ .... -o MyExe B A ImpLib A
>
> The last "A" is coming from target_link_libraries(B PUBLIC A) and the
> linker  is complaining that this last "A" has undefined symbols.
>
> Thanks.Giorgio.
>
>
>
>
>
>
>
>
> Il giorno mar 6 nov 2018 alle ore 06:59 Robert Maynard <
> robert.maynard at kitware.com> ha scritto:
>
>> You have order dependent static libraries which can be solved by
>> constructing a cycle. As Bo stated by constructing the cycle
>> B;A;ImportedExtLib;B;A each library can see each other.
>>
>> Looking at your original code example it looks like you are importing
>> the libraries as SHARED, but I think these are actually static
>> libraries and should be imported as such so that CMake does the
>> automatic cycle creation. In general CMake doesn't do cycle creation
>> for shared libraries as they are not link order dependent.
>> On Tue, Nov 6, 2018 at 8:51 AM Giorgio Scorzelli <scrgiorgio at gmail.com>
>> wrote:
>> >
>> > I read the docs about  LINK_INTERFACE_MULTIPLICITY    too.
>> > But I'm not in the situation of a "cyclic dependency" so I 'm not sure
>> if it solve my problem.
>> > In my case (with B A and ImpLib) what would be the syntax?
>> >
>> > Il giorno mar 6 nov 2018 alle ore 06:30 Robert Maynard <
>> robert.maynard at kitware.com> ha scritto:
>> >>
>> >> The target_link_libraries has a property called
>> >> LINK_INTERFACE_MULTIPLICITY that should help you out.
>> >>
>> https://cmake.org/cmake/help/v3.13/command/target_link_libraries.html#cyclic-dependencies-of-static-libraries
>> >>
>> >>
>> >> On Tue, Nov 6, 2018 at 8:24 AM scrgiorgio <scrgiorgio at gmail.com>
>> wrote:
>> >> >
>> >> > Thanks for the help,
>> >> >
>> >> > trying this (or any combination):
>> >> >
>> >> > target_link_libraries(MyExe B)
>> >> > target_link_libraries(MyExe A )
>> >> > target_link_libraries(MyExe ImpLib)
>> >> >
>> >> > I get this order:
>> >> >
>> >> > 'B;...whatever...;A;ImpLib"
>> >> >
>> >> > and the last past is causing the problem. Apparently there is no way
>> to
>> >> > change the right part (-Wl,--start-group -Wl,--end-groun sometimes
>> work,
>> >> > sometimes not).
>> >> > Any advice?
>> >> >
>> >> >
>> >> >
>> >> >
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