[CMake] Static Libraries and target_link_libraries

[Puetz Kevin A]

I often hit this, particularly with header-only INTERFACE libraries where I just want to pick up their defines/include paths, and then CMake ends up treating the target_link_libraries(PRIVATE as public anyway). So it would definitely be helpful to have a warning that this doesn’t do what you’d expect, and maybe a pointer to $<BUILD_INTERFACE:header_library> which seems to be the only way to actually have a private (not listed in the exported <project-config.cmake> dependency while building a static library.

From: CMake [mailto:cmake-bounces at cmake.org] On Behalf Of Marc CHEVRIER
Sent: Friday, January 25, 2019 8:54 AM
To: Cmake Mailing List <cmake at cmake.org>; Andrew Bell <andrew.bell.ia at gmail.com>
Subject: Re: [CMake] Static Libraries and target_link_libraries

It is quite inexact because a target can store many information like include directories or preprocessor definitions for example (through properties like INCLUDE_DIRECTORIES or COMPILE_DEFINITIONS).

So it make sense to enable to specify link libraries to a static library using PRIVATE or PUBLIC to ensure various settings are propagated to the static library compilation step.
Le 25 janv. 2019 à 15:46 +0100, Andrew Bell <andrew.bell.ia at gmail.com<mailto:andrew.bell.ia at gmail.com>>, a écrit :


When creating a static library, you can still use the function "target_link_libraries" even though the static library is never linked, as such.  What you're doing is creating a dependency record for cmake so that target_link_libraries of a static library are included in a link of some other target which depends on the static library.  What seems confusing is that target_link_libraries accepts the keywords PUBLIC and PRIVATE as well as INTERFACE when used with a static library, since only INTERFACE really makes sense in this context.

Would it be beneficial to issue a warning when someone uses PUBLIC or PRIVATE with target_link_libraries on a static library to make it clear that they may not be understanding what's going on?

--
Andrew Bell
andrew.bell.ia at gmail.com<mailto:andrew.bell.ia at gmail.com>
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