Since cmTarget::ComputeLinkInterface is called separately for each
"head" target that links a target, the warning we produce when
CMP0022 is not set could be repeated. Add explicit logic to allow
the warning to appear at most once. Multiple copies of the warning
for the same target are almost always identical and therefore
redundant. In the rare case that two copies of the warning are
different, the second can appear in a future run after the first
is fixed.
This property replaces the properties which
match (IMPORTED_)?LINK_INTERFACE_LIBRARIES(_<CONFIG>)?, and is enabled
for IMPORTED targets, and for non-IMPORTED targets only with a policy.
For static libraries, the INTERFACE_LINK_LIBRARIES property is
also used as the source of transitive usage requirements content.
Static libraries still require users to link to all entries in
their LINK_LIBRARIES, but usage requirements such as INCLUDE_DIRECTORIES
COMPILE_DEFINITIONS and COMPILE_OPTIONS can be restricted to only
certain interface libraries.
Because the INTERFACE_LINK_LIBRARIES property is populated unconditionally,
we need to compare the evaluated result of it with the link implementation
to determine whether to issue the policy warning for static libraries. For
shared libraries, the policy warning is issued if the contents of
the INTERFACE_LINK_LIBRARIES property differs from the contents of the
relevant config-specific old LINK_INTERFACE_LIBRARIES property.
Brad King
Stephen Kelly