How to use Howard Hinnant's date library with CPM?

[fgr]

I'm trying to use Howard Hinnant's date library with CPM.

This works:

CPMAddPackage(
        NAME HowardHinnant_date
        GITHUB_REPOSITORY HowardHinnant/date
        VERSION 3.0.0
)

But I have to use #include "include/date/date.h" to include the header. I want to get rid of the include part in the #include path (#include "date/date.h").

I tried

if(HowardHinnant_date_ADDED)
    target_include_directories( HowardHinnant_date INTERFACE
            ${HowardHinnant_date_SOURCE_DIR}/include )
endif()

But cmake complains that target HowardHinnant_date is not build in my cmake project. So I changed this into (using the actual target's name (e.g., myproject))

if(HowardHinnant_date_ADDED)
    target_include_directories( myproject INTERFACE
            ${HowardHinnant_date_SOURCE_DIR}/include )
endif()

But still the pre-processor cannot find date/date.h in #include "date/date.h".

[fgr]

Found a solution. Using target_include_directories was wrong. All I had to do was:

CPMAddPackage(
        NAME HowardHinnant_date
        GITHUB_REPOSITORY HowardHinnant/date
        VERSION 3.0.0
)

...

add_executable(mytarget_executable ...)

target_link_libraries(mytarget_executable date::date)

What I do not understand, though, is why I have to use date::date instead of something like HowardHinnant_date::HowardHinnant_date because the NAME property in CPMAddPackage() is HowardHinnant_date and not date.

[Andres6936]

It depends a lot on the documentation, in this case, the documentation of library you want to use is little.
But you should always try to check CMakeLists.txt and see which libraries are defined, for this case, look:

https://github.com/HowardHinnant/date/blob/313189b0a8767f9964704cfc87fe5956e12abc24/CMakeLists.txt#L62-L63

The library is being defined with the name date and an alias that is named date::date, so you should use date::date and not HowardHinnant_date::HowardHinnant_date.

[fgr]

Thanks for the clarification @Andres6936 I obviously have to learn more about CMake.

[fgr]

Added information on how to use the date library with CPM to the wiki.