Help/policy/CMP0053.rst
.. |REMOVED_IN_CMAKE_VERSION| replace:: 4.0 .. include:: include/REMOVED_PROLOGUE.rst
.. versionadded:: 3.1
Simplify variable reference and escape sequence evaluation.
CMake 3.1 introduced a much faster implementation of evaluation of the
:ref:Variable References and :ref:Escape Sequences documented in the
:manual:cmake-language(7) manual. While the behavior is identical
to the legacy implementation in most cases, some corner cases were
cleaned up to simplify the behavior. Specifically:
Expansion of @VAR@ reference syntax defined by the
:command:configure_file and :command:string(CONFIGURE)
commands is no longer performed in other contexts.
Literal ${VAR} reference syntax may contain only
alphanumeric characters (A-Z, a-z, 0-9) and
the characters _, ., /, -, and +.
Note that $ is technically allowed in the NEW behavior, but is
invalid for OLD behavior. This is due to an oversight during the
implementation of CMP0053 and its use as a literal variable
reference is discouraged for this reason.
Variables with other characters in their name may still
be referenced indirectly, e.g.
.. code-block:: cmake
set(varname "otherwise & disallowed $ characters") message("${${varname}}")
The setting of policy :policy:CMP0010 is not considered,
so improper variable reference syntax is always an error.
More characters are allowed to be escaped in variable names.
Previously, only ()#" \@^ were valid characters to
escape. Now any non-alphanumeric, non-semicolon, non-NUL
character may be escaped following the escape_identity
production in the :ref:Escape Sequences section of the
:manual:cmake-language(7) manual.
The OLD behavior for this policy is to honor the legacy behavior for
variable references and escape sequences. The NEW behavior is to
use the simpler variable expansion and escape sequence evaluation rules.
.. |INTRODUCED_IN_CMAKE_VERSION| replace:: 3.1 .. |WARNED_OR_DID_NOT_WARN| replace:: warned .. include:: include/REMOVED_EPILOGUE.rst