Is it possible to send return value via argument?

[stevenleeS0ht]

In Return Value, it recommends to set a variable to the parent scope to return a value from function.

But I am wondering if it is possible to return a value via argument of function. It is more commonly seen in CMake for example: ProcessorCount(N), N is a output argument of function.

Is the function argument in CMake passed by reference?

[ruslo]

if it is possible to return a value via argument of function

You're passing the name of the variable and in function you set this variable to PARENT_SCOPE.

It is more commonly seen in CMake for example: ProcessorCount(N), N is a output argument of function.

It's not common at all. It can be used for the functions with a trivial signature. Widely used approach is somefunc(SOMEPARAM somevalue). E.g.:

• https://cmake.org/cmake/help/latest/command/install.html
• https://cmake.org/cmake/help/latest/command/add_custom_command.html
• https://cmake.org/cmake/help/latest/command/execute_process.html

Is the function argument in CMake passed by reference?

There is no such thing in CMake language. It's the same PARENT_SCOPE:

• https://github.com/Kitware/CMake/blob/v3.14.4/Modules/ProcessorCount.cmake#L218

[ruslo]

Closing inactive discussion.