[CMake] POSITION_INDEPENDENT_CODE's [un]expected behaviour

[Craig Scott]

Thanks for the links. I've updated the relevant issue in gitlab and also
added links to other related ones so that the full picture is captured more
or less in one place. I'll ping the dev list to see if anyone has further
updates or thoughts on the PIE picture for executables. From a very quick
look, it may be non-trivial to get all compilers/platforms updated with the
correct options and at least one issue talks about problems with QT and
having PIE being enabled, but I'll defer to the dev list to provide further
insights. You can see the updated issue with links here:

https://gitlab.kitware.com/cmake/cmake/issues/14983



On Sat, Jul 22, 2017 at 3:01 AM, Oleksii Vilchanskyi via CMake <
cmake at cmake.org> wrote:

> Hello,
>
> I would like to ask about POSITION_INDEPENDENT_CODE target property. As
> of CMake 3.8.2 POSITION_INDEPENDENT_CODE appends -fPIE or -fPIC to
> CMAKE_<LANG>_FLAGS and CMAKE_EXE_LINKER_FLAGS when building an executable
> or a library respectively. However, to build a PIE -pie linker flag is
> additionally required. Thus POSITION_INDEPENDENT_CODE is not behaving as
> expected being a really easy to fix for someone aware with CMake codebase.
>
> Is there any reason why it wasn't added when the property was introduced?
> Somebody proposed introducing POSITION_INDEPENDENT_EXECUTABLE later on in
> addition to POSITION_INDEPENDENT_CODE to maintain backwards compatibility
> (I suppose policies are also a solution?).
>
> This email is the result of the thread
> <https://github.com/arsenm/sanitizers-cmake/issues/13> and the message
> <https://github.com/arsenm/sanitizers-cmake/issues/13#issuecomment-315532253>
> by Juan Navarro (big thanks to him), which fully summarizes CMake's
> POSITION_INDEPENDENT_CODE treatment and links to multiple bugs: this one
> <https://cmake.org/Bug/view.php?id=14983>, so far without attention, and this
> one <https://gitlab.kitware.com/cmake/cmake/issues/16382>, resolved for
> Android.
>
> Thank you.
>
> Regards,
> Oleksii Vilchanskyi
>
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-- 
Craig Scott
Melbourne, Australia
https://crascit.com
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