D16894: [ECM] use a macro to add compiler flags conditionally

[David Faure]

dfaure added a comment.


  Ah. You meant an "OR", I thought it was an "AND".   (as in `our known selection of compilers OR/AND appleclang supports it`)
  But things are certainly not clearer now with the name CONDITION, which doesn't imply either one.
  
  Aside from the AppleClang issue, I've had cases where a compiler flag was added in an unreleased version of the compiler, so it makes sense to me to have a way to have a TRY_IF condition.
  At the same time, I guess we can have SUPPORTED_IF for the cases where we know it's supported and we want to save time by not even checking it.
  Then one could say "TRY_IF apple and clang" for the flags that we want to double-check on appleclang, instead of the function having this black magic hardcoded inside.
  And this way we don't need to check flags that work on all versions of clang like -pedantic.
  
  In summary, I suggest having both SUPPORTED_IF and TRY_IF, and moving AppleClang magic out of the function.

REPOSITORY
  R240 Extra CMake Modules

REVISION DETAIL
  https://phabricator.kde.org/D16894

To: rjvbb, #build_system, kfunk
Cc: dfaure, kfunk, apol, kde-frameworks-devel, kde-buildsystem, #build_system, michaelh, ngraham, bruns
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