CMP0174

Added in version 3.31.

cmake_parse_arguments(PARSE_ARGV) defines a variable for an empty string after a single-value keyword.

One of the main reasons for using the PARSE_ARGV form of the cmake_parse_arguments() command is to more robustly handle corner cases related to empty values. The non-PARSE_ARGV form doesn't preserve empty arguments, but the PARSE_ARGV form does. For each single-value keyword given, a variable should be defined if the keyword is present, even if it is followed by an empty string.

Prior to CMake 3.31, no variable would be defined if the value given after a single-value keyword was an empty string. This meant the code could not detect the difference between the keyword not being given, and it being given but with an empty value, except by iterating over all the arguments and checking if the keyword is present.

For the OLD behavior of this policy, cmake_parse_arguments(PARSE_ARGV) does not define a variable for a single-value keyword followed by an empty string, or followed by no value at all.

For the NEW behavior, cmake_parse_arguments(PARSE_ARGV) always defines a variable for each keyword given in the arguments, even a single-value keyword with an empty string as its value or no value at all. With the NEW behavior, the code can robustly check if a single-value keyword was given using just if(DEFINED <prefix>_<keyword>).

This policy was introduced in CMake version 3.31. 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.