What to do with our default hidden visibility for symbols?

Jaroslaw Staniek staniek at kde.org
Fri Aug 14 10:01:47 BST 2015


Hi,
ECM's KDECompilerSettings.cmake contains:

 # Default to hidden visibility for symbols
 set(CMAKE_CXX_VISIBILITY_PRESET hidden)
 set(CMAKE_VISIBILITY_INLINES_HIDDEN 1)

This raises a warning [1] for CMake 3.3+ and ignores this.
Don't we want to set the old policy ​CMP0063 for now?
Or even prepare for removal of ​CMP0063 (see [2])?
I know, that would not be very soon.


[1] share/ECM/modules/ECMAddTests.cmake:97
(add_executable):
  Policy CMP0063 is not set: Honor visibility properties for all
target
  types.  Run "cmake --help-policy CMP0063" for policy details.  Use
the
  cmake_policy command to set the policy and suppress this
warning.


  Target "PluginsTest" of type "EXECUTABLE" has the following
visibility

  properties set for
CXX:



CXX_VISIBILITY_PRESET


VISIBILITY_INLINES_HIDDEN


  For compatibility CMake is not honoring them for this target.



[2]
​CMP0063
-------

Honor visibility properties for all target types.

The ``<LANG>_VISIBILITY_PRESET`` and
``VISIBILITY_INLINES_HIDDEN`` target properties affect visibility
of symbols during dynamic linking.  When first introduced these properties
affected compilation of sources only in shared libraries, module libraries,
and executables with the ``ENABLE_EXPORTS`` property set.  This
was sufficient for the basic use cases of shared libraries and executables
with plugins.  However, some sources may be compiled as part of static
libraries or object libraries and then linked into a shared library later.
CMake 3.3 and above prefer to honor these properties for sources compiled
in all target types.  This policy preserves compatibility for projects
expecting the properties to work only for some target types.

The ``OLD`` behavior for this policy is to ignore the visibility properties
for static libraries, object libraries, and executables without exports.
The ``NEW`` behavior for this policy is to honor the visibility properties
for all target types.

This policy was introduced in CMake version 3.3.  CMake version
3.3.0 warns when the policy is not set and uses ``OLD`` behavior.  Use
the ``cmake_policy()`` command to set it to ``OLD`` or ``NEW``
explicitly.

.. note::
  The ``OLD`` behavior of a policy is
  ``deprecated by definition``
  and may be removed in a future version of CMake.
​

-- 
regards, Jaroslaw Staniek

KDE:
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Qt Certified Specialist:
: http://www.linkedin.com/in/jstaniek
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