[CMake] Binaries linking interface library

[Robert Maynard]

The cause of the downstream failure ( cmake adds "-lLibMinimal" to the
linker ) is caused by the the cmake install(EXPORT) error.

You need to have LibMinimal in your export set so that CMake at export
time is aware that it is an interface library and generates the
correct import interface target to represent it. Without that
information you will generate an invalid information, and have an
invalid link line.

On Wed, Jan 16, 2019 at 2:37 AM Ciccio Pasticcio
<dodungocorporation at gmail.com> wrote:
>
> Hello all,
> I've got a simple, header only, interface library. Following the whole CMakeLists.txt
>
> CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
>
> INCLUDE(CommonLib)
> PROJECT(LibMinimal)
> ADD_LIBRARY(${PROJECT_NAME} INTERFACE )
>
> TARGET_INCLUDE_DIRECTORIES(${PROJECT_NAME}
>     INTERFACE "${PROJECT_SOURCE_DIR}/include"
>     INTERFACE "${PROJECT_SOURCE_DIR}/include/inc_arm"
> )
>
> INSTALL (DIRECTORY "include/"
>     DESTINATION ${INSTALL_LIBS_INCLUDE}
>     FILES_MATCHING
>         PATTERN "*.h"
>         PATTERN "*.hpp"
> )
>
> Then I use it in all my others libraries as follow:
>
> TARGET_LINK_LIBRARIES(<target> PRIVATE LibMinimal ...)
>
> When I build the whole source tree I get all my .so and .a, even if I get this error while configuring the whole source tree:
>
> CMake Error: install(EXPORT "hwifcTarget" ...) includes target "hwifc-static" which requires target "LibMinimal" that is not in the export set.
>
> hwifc is a static library. (I have other problem related to that library tho).
>
> When I link one of my library in an application cmake adds "-lLibMinimal" to the linker, why? INTERFACE library shouldn't produce any output, right? This obviously breaks the build, since there is no library file.
>
> Any idea?
>
> Thanks,
> Gabriele
>
>
>
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