[CMake] Generator Expressions and FetchContent

[Craig Scott]

Can you provide a small project example that can be used to demonstrate
your problem? The specifics of how you are doing things may be important.


On Sun, Mar 18, 2018 at 8:12 AM, Saad Khattak <saadrustam at gmail.com> wrote:

> Hi,
>
> ExternalProject_Add builds, generates and installs and thus any generator
> expressions used will be expanded by the time another library uses it.
>
> For example, if I add a library LibA using ExternalProject_Add, I can then
> query the target property INTERFACE_INCLUDE_DIRECTORIES and get the include
> directory for the library:
>
> get_target_property(LibA_INCLUDE_DIRECTORIES LibA
>   INTERFACE_INCLUDE_DIRECTORIES
>   )
>
> This allows me to then use the variable LibA_INCLUDE_DIRECTORIES in my
> CMake include(...) statements. However, with FetchContent, this is no
> longer possible.
>
> The reason I would like to query a variable is because at project
> generation time, I invoke FetchContent only if LibA is not found by
> find_package(LibA).
>
> Thus, the include directory for LibA may be in the current build directory
> (through FetchContent) OR it may be found in the folder where LibA is
> cloned by the user and generated/built OR an INSTALL of LibA.
>
> Perhaps I should not be using `get_target_property` to get the a library's
> include directory? Either way, would like some guidance in solving this
> issue.
>
> Thank you,
> Saad
>
>
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-- 
Craig Scott
Melbourne, Australia
https://crascit.com
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