Commit b8af2011 (cmTarget: Fix listing of source files at
configure-time., 2014-04-13) refactored a GetObjectLibrariesCMP0026
method out of GetLanguages. In flight, a conditional use of a target
if available was changed to an assert-available.
This code is only used to read the LOCATION property at configure
time, when the link information is incomplete, and not all targets
are defined, so the assert is inappropriate, even though it can lead
to incorrect information being generated. CMP0026 warns about the
potentially incorrect information anyway.
Restore support for the undocumented <CONFIG>_LOCATION target property
removed by commit v3.0.0-rc1~175^2 (cmTarget: Remove support for
<CONFIG>_LOCATION property, 2013-12-30) as part of the CMP0026 OLD
behavior.
The final location and name of a build-target is not determined
until generate-time. However, reading the LOCATION property from
a target is currently allowed at configure time. Apart from creating
possibly-erroneous results, this has an impact on the implementation
of cmake itself, and prevents some major cleanups from being made.
Disallow reading LOCATION from build-targets with a policy. Port some
existing uses of it in CMake itself to use the TARGET_FILE generator
expression.
Stephen Kelly