[cmake-developers] [PATCH] FindProtobuf: fix wrong library list for Unix

[Antonio Pérez Barrero]

El mar., 9 feb. 2016 a las 11:13, Rolf Eike Beer (<eike at sf-mail.de>)
escribió:

> Am 09.02.2016 11:10, schrieb Antonio Pérez Barrero:
> >>
> >> On 02/08/2016 04:24 PM, Antonio Pérez Barrero wrote:
> >> > Yes, it is possible, but currently it's not looking for the debug
> >> > library with a different name, just in a different path that is
> >> > unlikely to exist in a Unix system.
> >>
> >> The fact that a separate find_library is called for it and the result
> >> is stored in a separate (user-settable) cache entry means that it is
> >> possible to get two different values.  This convention is well
> >> established
> >> in several find modules.
> >>
> >> > Having the PROTOBUF_LIBRARIES variable getting the afore mentioned
> >> > value messes up the client code using `find_package(Protobuf)` on
> Unix.
> >>
> >> The only supported use for PROTOBUF_LIBRARIES is to pass it to
> >> target_link_libraries, and that interprets the 'optimized' and 'debug'
> >> keywords.  This is shown in the module documentation example:
> >>
> >>     target_link_libraries(bar ${PROTOBUF_LIBRARIES})
> >>
> >> The documentation makes no other guarantees about the variable value.
> >>
> >
> > Thanks for your explanantion, that makes sense. I had issues because I
> > was
> > appending the value of PROTOBUF_LIBRARIES to a list and then removing
> > duplicates before calling `target_link_libraries(bar ${LIST})`. So when
> > the
> > PROTOBUF_LIBRARIES values was
> > `optimized;/usr/lib/libprotobuf.so;debug;/usr/lib/libprotobuf.so` I was
> > missing the link flag for /usr/lib/libprotobuf.so in Debug builds.
> > Skipping
> > the duplicates removal step solves my issue.
> >
> > Anyway, the root cause is the `find_library` is finding the same
> > library
> > for optimized and debug configuration. So, would a patch like this be
> > benefial?
> >
> > diff --git a/Modules/FindProtobuf.cmake b/Modules/FindProtobuf.cmake
> > index 2f13b09..35929a4 100644
> > --- a/Modules/FindProtobuf.cmake
> > +++ b/Modules/FindProtobuf.cmake
> > @@ -224,7 +224,7 @@ function(_protobuf_find_libraries name filename)
> >         PATHS
> > ${PROTOBUF_SRC_ROOT_FOLDER}/vsprojects/${_PROTOBUF_ARCH_DIR}Debug)
> >     mark_as_advanced(${name}_LIBRARY_DEBUG)
> >
> > -   if(NOT ${name}_LIBRARY_DEBUG)
> > +   if((NOT ${name}_LIBRARY_DEBUG) OR (${name}_LIBRARY STREQUAL
> > ${name}_LIBRARY_DEBUG))
> >        # There is no debug library
> >        set(${name}_LIBRARY_DEBUG ${${name}_LIBRARY} PARENT_SCOPE)
> >        set(${name}_LIBRARIES     ${${name}_LIBRARY} PARENT_SCOPE)
>
> Just use SelectLibraryConfigurations, that does the same automatically
> if they are identical, and also handles the cases where only debug, but
> not release is found.
>

Thanks, I tried that and got it working. I'll submit another patch as the
change covers a related but different issue.

Regards,
Antonio



> Greetings,
>
> Eike
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