[CMake] Override of link flag for one specific shared library

[Martin Apel]

I resorted to turn off the flags for the complete directory. In this
case, this was possible, because they were only intended to speed up
C++-template instantiation. So for this one directory template
instantiation is handled in the slower way, but I can live with that.
However, I think there should be a way to override flags for a single
target. The easiest way from my point of view would be to adjust the
CMake-rules to contain the target-specific flags after the global flags,
not before.

Regards,

Martin

David Cole wrote:
> ADD_SUBDIRECTORY is the "right" thing to be using. SUBDIRS is
> deprecated, but they process things subtly differently, so I just
> wanted to rule out that you might be encountering a "SUBDIRS side
> effect"...
>
> You've ruled it out.
>
> Could you re-organize such that libraries with different flags are in
> different CMakeLists files?
>
>
> On Mon, Sep 8, 2008 at 3:02 AM, Martin Apel <martin.apel at simpack.de
> <mailto:martin.apel at simpack.de>> wrote:
>
>     I am using ADD_SUBDIRECTORY. I did'nt know, that anything like SUBDIRS
>     exists and haven't found anything in the documentation about it.
>
>     Martin
>
>
>     David Cole wrote:
>     > Are you using SUBDIRS or ADD_SUBDIRECTORY in your project...?
>     >
>     >
>     > On Thu, Sep 4, 2008 at 2:42 AM, Martin Apel
>     <martin.apel at simpack.de <mailto:martin.apel at simpack.de>
>     > <mailto:martin.apel at simpack.de <mailto:martin.apel at simpack.de>>>
>     wrote:
>     >
>     >     Unfortunately this does not work. It seems that CMake
>     generates all
>     >     libraries defined in one CMakeLists.txt with the setting of
>     >     CMAKE_SHARED_LINKER_FLAGS at the end of the file.
>     >     This causes this setting to be applied to all libraries in the
>     >     CMakeLists.txt. As I have 4 libraries in this one
>     CMakeLists.txt, this
>     >     doesn't help much.
>     >
>     >     I tried to do something like the following:
>     >     SET (CMAKE_SHARED_LINKER_FLAGS "${ORIG_SHARED_LINKER_FLAGS}")
>     >     ADD_LIBRARY (FortranInterface ${OBJS})
>     >     SET (CMAKE_SHARED_LINKER_FLAGS
>     "${MODIFIED_SHARED_LINKER_FLAGS}")
>     >     but the FortranInterface library gets built with
>     >     MODIFIED_SHARED_LINKER_FLAGS in effect.
>     >
>     >     I would suggest to change the order of items in the build
>     rules for a
>     >     future CMake release, such that it's possible to override
>     general
>     >     flags
>     >     with a target specific property. Today the link
>     >     rules look as follows:
>     >     SET(CMAKE_CXX_CREATE_SHARED_LIBRARY "<CMAKE_CXX_COMPILER> ...
>     >     <LINK_FLAGS> <CMAKE_SHARED_LIBRARY_CREATE_CXX_FLAGS> ....")
>     >     >From my point of view it would be better to put LINK_FLAGS
>     to the
>     >     end of
>     >     the list (not only for shared libraries, but in general).
>     >
>     >     Regards,
>     >
>     >     Martin
>     >
>     >     David Cole wrote:
>     >     > Maybe save and restore the CMAKE_SHARED_LINKER_FLAGS
>     around your
>     >     reset
>     >     > of it in the sub-CMakeLists.txt...?
>     >     >
>     >     >
>     >     > On Wed, Sep 3, 2008 at 10:41 AM, Martin Apel
>     >     <martin.apel at simpack.de <mailto:martin.apel at simpack.de>
>     <mailto:martin.apel at simpack.de <mailto:martin.apel at simpack.de>>
>     >     > <mailto:martin.apel at simpack.de
>     <mailto:martin.apel at simpack.de> <mailto:martin.apel at simpack.de
>     <mailto:martin.apel at simpack.de>>>>
>     >     wrote:
>     >     >
>     >     >     Hi,
>     >     >
>     >     >     I have defined the following in a top-level
>     CMakeLists.txt:
>     >     >      SET (CMAKE_SHARED_LINKER_FLAGS
>     "${CMAKE_SHARED_LINKER_FLAGS}
>     >     >     -Wl,--unresolved-symbols=ignore-in-shared-libs")
>     >     >
>     >     >     Now I'd like to reset this for one specific library in a
>     >     subdirectory
>     >     >     (in a separate CMakeLists.txt added with
>     ADD_SUBDIRECTORY to
>     >     the main
>     >     >     CMakeLists.txt). I tried to use
>     >     >      SET_TARGET_PROPERTIES (FortranInterface PROPERTIES
>     LINK_FLAGS
>     >     >     -Wl,--unresolved-symbols=ignore-in-object-files")
>     >     >     which reverses the effect of "ignore-in-shared-libs".
>     >     >     Unfortunately the
>     >     >     linker rule contains the LINK_FLAGS before
>     >     >     CMAKE_SHARED_LINKER_FLAGS, so
>     >     >     this cannot be used to override the setting. I have
>     also tried
>     >     >     resetting
>     >     >     CMAKE_SHARED_LINKER_FLAGS in the sub-CMakeLists.txt,
>     but then it
>     >     >     applies
>     >     >     to all other
>     >     >     libraries handled in this CMakeLists.txt as well.
>     >     >
>     >     >     Any ideas, how I can solve this problem?
>     >     >
>     >     >     Regards,
>     >     >
>     >     >     Martin
>     >     >
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