How to Pass an Argument With No Value to Cmake?

If you need to pass an argument with no value to CMake, you can simply include the argument without specifying a value. For example, if you are using the command line, you can pass the argument like this:

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cmake -DARGUMENT_NAME ..

In your CMakeLists.txt file, you can check if the argument was passed using the DEFINED keyword. For example, if you want to check if the argument ARGUMENT_NAME was passed without a value, you can use the following syntax:

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if(ARGUMENT_NAME)
   message("Argument passed with no value")
endif()

This way, you can handle arguments with no values in your CMake build system.

How can you prevent passing a value for an argument in CMake?

One way to prevent passing a value for an argument in CMake is to check the value of the argument within the CMake script and set a default value if one is not provided. This can be done using the if and else statements in CMake.

For example, you can check if the argument is empty and set a default value if it is not provided by the user:

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if(NOT ARGUMENT)
    set(ARGUMENT "default_value")
endif()

This way, if the user does not pass a value for the argument, it will be set to the default value specified in the script.

Additionally, you can also use the OPTIONAL keyword when defining the arguments in a SET or ARGUMENT command to indicate that the argument is optional and does not need to be provided by the user:

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option(ARGUMENT "Description of argument" OFF)

By setting the argument as optional, the user is not required to provide a value for it when running the CMake script.

How to handle optional arguments with no values in CMake?

In CMake, you can handle optional arguments with no values by using the OPTION command along with a default value or by checking if the argument was specified. Here are two ways to handle optional arguments with no values in CMake:

1. Using the OPTION command with a default value:

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option(MY_OPTION "Enable some feature" OFF)

if(MY_OPTION)
    message("MY_OPTION is enabled")
else()
    message("MY_OPTION is not enabled")
endif()

In this example, MY_OPTION is an optional argument that does not have a value. By default, it is set to OFF. You can toggle its value by setting it to ON in the CMake command line or script.

1. Checking if the argument was specified:

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if(DEFINED MY_ARGUMENT)
    message("MY_ARGUMENT is specified")
else()
    message("MY_ARGUMENT is not specified")
endif()

In this example, MY_ARGUMENT is an optional argument that does not have a value. You can check if it was specified by using the DEFINED keyword in an if statement.

These are two ways you can handle optional arguments with no values in CMake. Choose the one that best fits your use case and requirements.

How to create conditional logic based on arguments with no values in CMake?

In CMake, you can use the "if" statement to create conditional logic based on arguments with no values. Here is an example of how you can achieve this:

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option(ENABLE_FEATURE "Enable a feature" OFF)

if(ENABLE_FEATURE)
    message("Feature is enabled")
    # Add your logic here for when the feature is enabled
else()
    message("Feature is disabled")
    # Add your logic here for when the feature is disabled
endif()

In this example, the option command creates an argument named ENABLE_FEATURE with no value specified. The if statement checks if the argument is set to ON (i.e., if it has been specified on the command line), and then executes the corresponding logic based on whether the feature is enabled or disabled.

You can run CMake with the following commands:

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cmake -DENABLE_FEATURE=ON .
make

This will enable the feature and execute the logic inside the if statement. If you omit the -DENABLE_FEATURE=ON option when running CMake, the feature will be disabled, and the logic inside the else statement will be executed.

What are the potential pitfalls of passing arguments that are empty in CMake?

There are a few potential pitfalls of passing empty arguments in CMake:

1. Unintended behavior: If a CMake function or macro expects a non-empty argument but receives an empty argument, it may not behave as expected and could lead to errors or unpredictable behavior.
2. Variable scope issues: If you pass an empty argument to a CMake function that sets a variable, the variable may not be set correctly or may retain its previous value, leading to unexpected results in subsequent parts of the CMake script.
3. Difficulty in debugging: If your CMake script contains calls to functions or macros with empty arguments, it may be difficult to track down issues or debug problems, as the source of the error may not be immediately obvious.
4. Maintenance issues: Passing empty arguments can make your CMake scripts harder to maintain and understand, especially for other developers who may be working on the project in the future.

Overall, it is important to be mindful of passing empty arguments in CMake and to ensure that all function calls and macro invocations are properly handled to avoid potential pitfalls.