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| -rw-r--r-- | Help/command/unset.rst | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/Help/command/unset.rst b/Help/command/unset.rst index a1fc95c..c19dd31 100644 --- a/Help/command/unset.rst +++ b/Help/command/unset.rst @@ -7,9 +7,16 @@ Unset a variable, cache variable, or environment variable. unset(<variable> [CACHE | PARENT_SCOPE]) -Removes the specified variable causing it to become undefined. If -``CACHE`` is present then the variable is removed from the cache instead -of the current scope. +Removes a normal variable from the current scope, causing it +to become undefined. If ``CACHE`` is present, then a cache variable +is removed instead of a normal variable. Note that when evaluating +:ref:`Variable References` of the form ``${VAR}``, CMake first searches +for a normal variable with that name. If no such normal variable exists, +CMake will then search for a cache entry with that name. Because of this +unsetting a normal variable can expose a cache variable that was previously +hidden. To force a variable reference of the form ``${VAR}`` to return an +empty string, use ``set(<variable> "")``, which clears the normal variable +but leaves it defined. If ``PARENT_SCOPE`` is present then the variable is removed from the scope above the current scope. See the same option in the :command:`set` command |