The <LANG>_VISIBILITY_PRESET and VISIBILITY_INLINES_HIDDEN were first
merged in commit v2.8.12~322 (Merge topic 'VISIBILITY_PRESET-property',
2013-06-05) but worked only for shared libraries and executables with
exports. Prior to commit v3.0.0-rc1~581^2 (GenerateExportHeader:
Deprecate add_compiler_export_flags function., 2013-09-02) the
add_compiler_export_flags function was used to add visibility flags to
all targets.
The visibility flags are useful for sources in all target types because
they may be later linked into shared libraries or executables with
exports. Introduce policy CMP0063 to enable them for all target types
while preserving compatibility with existing projects that do not expect
this.
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