A global map models an association between a name and one or more [key, value] pairs. In the implementation, these pairs are saved by the calls to
set_property(GLOBAL PROPERTY ${prefix}${key} ${value})A prefix usually identifies a program context, so that different global maps separate different contexts. A global map maintains an index of the keys it stores, which can be used to find out whether a property is in the map or not. A map can also be cleared with the help of its index. It's possible to set, unset, or append to a property using syntax similar to that of usual variables:
# set(variable value)
global_set(context variable value)
# get_property(GLOBAL PROPERTY variable value)
global_set(context variable value)
# unset(variable)
global_unset(context variable)
# list(APPEND variable value)
global_append(context variable value)The first argument is always a map name; it limits the scope of the operation to a certain context. It's convenient to think of this argument as of a map name, although in implementation it's just a prefix of the stored keys.
Sometimes, a CMake function or a module can have a complex state. In such cases, writing something like
get_property(value GLOBAL PROPERTY property)
set_property(GLOBAL PROPERTY property ${value} ${additional_value})just to append a value to an existing property becomes a tedious, error-prone task.
.. cmake-module:: ../../cmake/GlobalMap.cmake