[CMake] Best way to combine generated static libraries into a single static library

Fri Sep 21 12:38:45 EDT 2018

Hi David,

It didn't give me error info. It can produce the final static library, but
the contents of third party static libraries are not included.

Also, sorry for the mistake I have made in my previous email. Deniz is
right, the keyword "PUBLIC" should be used in target_link_librarie().

Thanks

On Fri, Sep 21, 2018 at 10:06 AM David Jobet <djobet at tower-research.com>
wrote:

> Hello,
>
> glad that could help you.
> For your newer problem, you don't describe them, so it's tough to know
> what kind of problems you're facing.
> Maybe a small example of your CMakeLists.txt + a capture of the error
> cmake gives you could help ?
>
> David
> On Fri, Sep 21, 2018 at 4:52 PM Ke Gao <ke.gao.ut at gmail.com> wrote:
> >
> > Thank you all for the help.
> >
> > I finally use a way quite similar to David's first approach. I first
> generate all sub-projects into object libraries using add_library(lib1
> OBJECT SOURCES). Then in the final library, I use
> add_library(single_static_lib STATIC SOURCES) and target_link_libraries(
> single_static_lib lib1 lib2 ...). Note that I didn't use "
> $<TARGET_OBJECTS:lib1>" in the final "add_library" and also didn't use
> "PUBLIC" keyword in the final "target_link_libraries". It works on CMake
> v3.12.2 and gives me a single static lib which combines all the objs I want.
> >
> > But currently I still have problems of further combining third party
> static libraries into the final generated static single_static_lib. Can
> anybody provide a solution for this?
> >
> > Thank you very much.
> >
> > Ke
> >
> > On Fri, Sep 21, 2018 at 6:15 AM Deniz Bahadir <dbahadir at benocs.com>
> wrote:
> >>
> >> Am 21.09.2018 um 09:33 schrieb David Jobet:
> >> > Hello,
> >> >
> >> > I had a similar issue lately and wanted to "pack" several static libs
> >> > into a dynamic one. (Not even talking about an INTERFACE lib since I
> >> > really wanted that .so)
> >> > I made it work with 3 different solutions, none of them being "clean"
> >> > from my point of view.
> >> >
> >> > 1- OBJECT libs on sub projects : add_library(lib1 OBJECT SOURCES) and
> >> > for the single static lib : add_library(single_static_lib STATIC
> >> > $<TARGET_OBJECTS:lib1> ...)
> >> > Problem I faced : since OBJECT libs do not support
> >> > target_link_libraries(), I had to remove the existing one and move
> >> > them instead to the target_include_directories() using generators.
> >>
> >> This is no longer true. Since CMake 3.12 `target_link_libraries` fully
> >> supports OBJECT libraries. You just need to pay attention to the special
> >> case of linking an OBJECT library with keyword "PUBLIC". (Object-files
> >> are always private and inherited object-files are therefore never
> >> further inherited. See:
> >>
> https://cmake.org/cmake/help/v3.12/command/target_link_libraries.html#linking-object-libraries
> )
> >>
> >> > e.g : target_include_directories(lib1 PUBLIC
> >> > $<TARGET_PROPERTY:another_lib,INCLUDE_DIRECTORIES>)
> >> > Because I had a dependency to a protobuf generated lib, I also had to
> >> > add manual add_dependencies to respect proper build order.
> >> > Not clean at all
> >> >
> >> > 2- add_library(mysharedlib STATIC CMakeLists.txt)
> >> > target_linked_libraries(mysharedlib PUBLIC lib1 ...)
> >> > Maybe the cleanest way I found.
> >> > The trick with CMakeLists.txt is that add_library needs at least one
> >> > source file. You can put any kind of files you want. CMakeLists.txt is
> >> > not compilable, so no extra compilation step, no need for dummy empty
> >> > source file and add_library is happy.
> >> > It did not work in my case because of problems related to how our .so
> >> > are used/generated. (problems at runtime with duplicated symbols in
> >> > protobufs)
> >> >
> >> > 3- a variation around 1
> >> > instead of defining OBJECT libs, define a variable holding all the
> >> > sources for lib1, another for lib2, ...
> >> > then just do add_library(mysharedlib STATIC ${SOURCES_FOR_lib1}
> >> > ${SOURCES_FOR_lib2})
> >> > It works a little bit like 1) but does not have any of its problems
> >> > (target_link, add_dependencies, generators, ...)
> >> > It has new problems of its own though : if your libs live in different
> >> > subfolders, the variables might not be visible from your
> >> > add_library(mysharedlib...) call.
> >> > To work around that, you can use PARENT_SCOPE (not sure if that works
> >> > accross several levels), or includes (defines those variables into
> >> > separate files living in each subfolders and include them in the
> >> > parent CMakeLists).
> >> >
> >> > Hope this helps (and I'd be happy to know of other ways)
> >> >
> >> > David
> >> > On Thu, Sep 20, 2018 at 5:45 PM Ke Gao <ke.gao.ut at gmail.com> wrote:
> >> >>
> >> >> Hi,
> >> >>
> >> >> I have a project which includes many sub-projects. Each sub-project
> generates a static library. In the main project, I want to combine the
> generated objs, generated static libraries from other sub-projects, and
> some other third party static libraries together into a single static
> library. Is there an elegant way to do this, or maybe an existing function?
> >> >>
> >> >> Thank you very much.
> >> >>
> >> >> --
> >> >>
> ..............................................................................................................................................
> >> >> Ke Gao
> >>
> >>
> >> Hope that information was of value,
> >> Deniz
> >>
> >> --
> >>
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> >
> >
> > --
> >
> ..............................................................................................................................................
> > Ke Gao
> --
>
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-- 
..............................................................................................................................................
Ke Gao
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