CMP0053

警告

該方針的 OLD 行為已在 CMake 版本 4.0 中移除。該方針必須透過呼叫 cmake_minimum_required() 或 cmake_policy() 設定為 NEW。

在 3.1 版被加入.

Simplify variable reference and escape sequence evaluation.

CMake 3.1 introduced a much faster implementation of evaluation of the 變數參照 and 跳脫序列 documented in the 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 configure_file() and 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.

  set(varname "otherwise & disallowed $ characters")
  message("${${varname}}")
  

• The setting of 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 跳脫序列 section of the 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.

This policy was introduced in CMake version 3.1. Prior to removal in CMake version 4.0, it could be set by cmake_policy() or cmake_minimum_required(). If it was not set, CMake warned, and used OLD behavior.