# CMP0200

Added in version 4.2.

Location and configuration selection for imported targets is more consistent.

The way CMake historically selected the configuration to use for imported targets prioritized selection based on location properties for a candidate configuration and only considered `IMPORTED_CONFIGURATIONS` as a fallback. This could result in incorrect configuration selection especially for `INTERFACE` libraries.

CMake 4.2 and above consider `IMPORTED_CONFIGURATIONS` to be a definitive list of available configurations, regardless of whether a configuration specific location is provided for the library. Additionally, CMake will respect non-configuration-specific locations when a configuration specific location is not specified.

This policy provides compatibility with projects that rely on the historical behavior. The policy setting applies to targets and is recorded at the point an imported target is created. Accordingly, imported packages may override the policy set by the consumer for targets they create. In particular, targets imported from Common Package Specification packages always use the `NEW` behavior.

The `OLD` behavior for this policy is to retain the historic behavior. The `NEW` behavior prioritizes selection based on the advertised list of available configurations. Both behaviors are described in detail below.

This policy was introduced in CMake version 4.2. It may be set by `cmake_policy()` or `cmake_minimum_required()`. If it is not set, CMake warns, and uses `OLD` behavior.

Note

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

## Mapped configuration selection

If `MAP_IMPORTED_CONFIG_<CONFIG>` (where `<CONFIG>` is the configuration of the consuming target) is set on an imported target, CMake would historically select from that list the first configuration which provides a configuration-specific location. If no such configuration exists, CMake would selects the consuming target's configuration, if the imported target is an `INTERFACE` library. Otherwise, CMake considers the target as not having a suitable configuration.

For `INTERFACE` libraries which do not provide a location, this results in CMake always selecting the consuming target's configuration and effectively ignoring `MAP_IMPORTED_CONFIG_<CONFIG>`. This behavior is not consistent with configuration selection for imported targets which provide a location.

Under the `NEW` behavior, CMake selects the first configuration from the mapping which appears in `IMPORTED_CONFIGURATIONS`. If `IMPORTED_CONFIGURATIONS` is not set, CMake selects the first configuration from the mapping which is "usable". For non-`INTERFACE` libraries, "usable" means that a location (either configuration-specific or configuration-agnostic) is available. `INTERFACE` libraries are always considered "usable".

If no match is found, CMake considers the target as not having a suitable configuration.

## Non-mapped configuration selection

If `MAP_IMPORTED_CONFIG_<CONFIG>` is not set, CMake would historically select the first configuration which provides a location out of the following:

- The consuming target's configuration, or

- The empty configuration, or

- The list of configurations in `IMPORTED_CONFIGURATIONS`.

As an implementation artifact, this results in CMake selecting the last configuration in `IMPORTED_CONFIGURATIONS` for `INTERFACE` libraries which do not provide a location. Again, this behavior is not consistent with configuration selection for imported targets which provide a location.

Under the `NEW` behavior, if `IMPORTED_CONFIGURATIONS` is set, CMake will select the consuming target's configuration if present therein, otherwise CMake will select the first imported configuration. If `IMPORTED_CONFIGURATIONS` is not set, CMake will select the consuming target's configuration if it is "usable" (as defined in the previous section); otherwise, CMake considers the target as not having a suitable configuration.

## Examples

Consider the following imported library:

    add_library(test INTERFACE IMPORTED)
    set_target_properties(test PROPERTIES
      IMPORTED_CONFIGURATIONS "RELEASE;DEBUG"
      INTERFACE_COMPILE_DEFINITIONS "$<$<CONFIG:debug>:DEBUG>"
    )

Under the `OLD` policy, CMake will select the `DEBUG` configuration of `test` (and thus define the symbol `DEBUG`) for any target linking to `test`, because CMake does not consider any configuration "valid", and, as an implementation artifact, the last configuration considered is accepted.

Under the `NEW` policy, the `RELEASE` configuration will be selected if the consuming project is built in any configuration other than `Debug` (keeping in mind that configuration matching is case-insensitive). This is because `DEBUG` will be preferred if the consumer's configuration is also `DEBUG`, but `RELEASE` will be preferred otherwise because it appears first in `IMPORTED_CONFIGURATIONS`, and its appearance therein makes it a "valid" configuration for an `INTERFACE` library.