Add ENABLE_<package> compile definitions for optional packages

Summary

Optional (external) packages are not linked into a module library directly, but might be linked later using cmake functions add_dune_<package>_flags or similar. In order to detect whether a package can be used, we thus have to do two checks:

1. Is the package found in the system?
2. Has the user linked the library?

The first check is done by cmake. If a find_package(<package>) is called, a corresponding <package>_FOUND variable is set. We additionally set HAVE_<package> in cmake and introduce a conditional define in the config.h file. But finding the package does not mean it is linked against a target. This can be done (for optional packages) manually, by calling the add_dune_<package>_flags macro. Unfortunately, we have no way of knowing whether a library will be linked. Thus we need to communicate this to the target using a compile flag, called ENABLE_<package>. The config.h then defines

#define HAVE_<package> ENABLE_<package>

With this MR, I introduce these missing ENABLE_<package> compile flags to some optional packages.

Related Issue

issue #252 (closed)

added buildsystem label

Why would you remove the quotation marks? They are perfectly right. Later in this change, for TBB you are adding quotations marks.

Yes, there are some stylistic changes without any improvement of the functionality. I tried to introduce consistency in style in all the AddXXXFlags.cmake files. Quotation mark or no quotation marks is not the question here :-) It does not make any difference. I have used quotation marks in dune_Register_package_flags and no quotation marks in the target_compile_definitions, but at the end one could remove it completely.

changed this line in version 3 of the diff

undone.

I like this change, as it makes thinks more consistent.

If I remember correctly, in the old Autotools-based build system Metis was treated without the ENBLE trick and we mimicked this behavior. I see no reason to stick to it.

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• 115e3055 - Add ENABLE_<package> compile definitions for optional packages

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• efb613f3 - Add ENABLE_<package> compile definitions for optional packages

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merged

mentioned in commit d5192b28

mentioned in merge request dune-istl!511 (closed)

mentioned in merge request dune-istl!509 (merged)