Am 21.09.2018 um 18:38 schrieb Ke Gao:
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.
Some clarification regarding STATIC and OBJECT library targets and how
they interact with each other using `target_link_libraries`:
A STATIC library target A can be linked (via `target_link_libraries`) to
another STATIC library target B.
`target_link_libraries(A STATIC PUBLIC B)`
However, the resulting library file libB does not contain the
information (aka object-files) of libA.
Instead, CMake makes sure to link both static library files libB and
libA when e.g. creating an executable exeC1 using target C1 which just
links (via `target_link_libraries`) to target B.
`target_link_libraries(C1 EXECUTABLE PUBLIC B)`
(Instead of an executable exeC1 you could have created a shared library
libC1 instead. The behavior is the same.)
If you instead want to create a combined, single STATIC library libC2,
which contains the object-files archived in both static library files
libA and libB created from targets A and B, then you somehow need to
extract the archived object-files from libA and libB. I am not sure if
CMake provides a (simple) way to do this.
For OBJECT libraries the behavior is like this:
An OBJECT library target X can be linked (via `target_link_libraries`)
to another OBJECT library target Y.
`target_link_libraries(Y OBJECT PUBLIC X)`
This, however, only transports the usage-requirements
(preprocessor-defines, include-paths etc.) from X to Y. The object-files
of X are in no way referenced by Y.
So, if you then create a STATIC target Z1 that links (via
`target_link_libraries`) to Y,...
`target_link_libraries(Z1 STATIC PUBLIC Y)`
... Z1 will reference/contain the usage-requirements of X and Y and the
object-files of Y, but not the object-files of X. (The static library
file libZ1 resulting from Z1 will contain the object-libraries of Y but
not of X.)
What you should do instead is not to link the OBJECT targets X and Y
together but instead only link them (explicitly) to the STATIC target Z2:
`target_link_libraries(Z2 STATIC PUBLIC Y X)`
Z2 then references the usage-requirements as-well-as object-files of
both OBJECT targets X and Y and the resulting static library file libZ2
will then contain the object-files of both library targets, X and Y.
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
You're welcome.
Deniz
On Fri, Sep 21, 2018 at 10:06 AM David Jobet <djo...@tower-research.com
<mailto:djo...@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...@gmail.com
<mailto:ke.gao...@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
<dbaha...@benocs.com <mailto:dbaha...@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...@gmail.com
<mailto:ke.gao...@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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