diff options
Diffstat (limited to 'Help/policy/CMP0174.rst')
| -rw-r--r-- | Help/policy/CMP0174.rst | 24 |
1 files changed, 14 insertions, 10 deletions
diff --git a/Help/policy/CMP0174.rst b/Help/policy/CMP0174.rst index bde0a03..748fdba 100644 --- a/Help/policy/CMP0174.rst +++ b/Help/policy/CMP0174.rst @@ -10,21 +10,25 @@ One of the main reasons for using the ``PARSE_ARGV`` form of the :command:`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 followed by a -value. Prior to CMake 3.31, no variable would be defined if the value given -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. +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, :command:`cmake_parse_arguments(PARSE_ARGV)` does not define a variable for a -single-value keyword followed by an empty string. +single-value keyword followed by an empty string, or followed by no value at +all. + For the ``NEW`` behavior, :command:`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. With the ``NEW`` behavior, the -code can robustly check if a single-value keyword was given with any value -using just ``if(DEFINED <prefix>_<keyword>)``. +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>)``. .. |INTRODUCED_IN_CMAKE_VERSION| replace:: 3.31 .. |WARNS_OR_DOES_NOT_WARN| replace:: warns |