How to Check If A Macro Exists In Cmake?

To check if a macro exists in CMake, you can use the if command with the DEFINED keyword followed by the macro name. For example, you can use the following syntax:

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if(DEFINED MY_MACRO)
    message("Macro MY_MACRO exists")
else()
    message("Macro MY_MACRO does not exist")
endif()

This will check if the macro MY_MACRO is defined in your CMake code, and print a message accordingly. You can replace MY_MACRO with the name of the macro you want to check. This method can be used to conditionally execute certain parts of your CMake code based on the existence of a specific macro.

How to determine if a specific macro is present in CMake?

To determine if a specific macro is present in CMake, you can use the CHECK_C_SOURCE_RUNS function in CMake. This function checks if the specified C source code compiles and runs successfully. You can create a C source file that contains a check for the specific macro and then use the CHECK_C_SOURCE_RUNS function to check if the macro is present.

Here is an example of how you can use the CHECK_C_SOURCE_RUNS function to determine if a specific macro is present in CMake:

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# Create a C source file containing a check for the specific macro
file(WRITE ${CMAKE_BINARY_DIR}/check_macro.c "
#include <stdio.h>
int main() {
    #if defined(MY_MACRO)
        printf(\"Macro MY_MACRO is present\");
    #else
        printf(\"Macro MY_MACRO is not present\");
    #endif
    return 0;
}
")

# Use CHECK_C_SOURCE_RUNS to check if the C source code compiles and runs successfully
CHECK_C_SOURCE_RUNS("
#include <stdio.h>
int main() {
    #if defined(MY_MACRO)
        printf(\"Macro MY_MACRO is present\");
    #else
        printf(\"Macro MY_MACRO is not present\");
    #endif
    return 0;
}
" MY_MACRO_PRESENT)

if(MY_MACRO_PRESENT)
    message("Macro MY_MACRO is present")
else()
    message("Macro MY_MACRO is not present")
endif()

In this example, we first create a C source file check_macro.c that contains a check for the specific macro MY_MACRO. We then use the CHECK_C_SOURCE_RUNS function to check if the C source code in the file compiles and runs successfully. Finally, we check the value of the MY_MACRO_PRESENT variable to determine if the specific macro is present in CMake.

What is the recommended approach for checking if a macro exists in CMake?

One recommended approach for checking if a macro exists in CMake is to use the if() command along with the DEFINED keyword to check if the macro is defined.

For example, you can check if a macro named MY_MACRO is defined using the following code:

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if(DEFINED MY_MACRO)
    message("Macro MY_MACRO is defined")
else()
    message("Macro MY_MACRO is not defined")
endif()

This code will check if the macro MY_MACRO is defined and print a message accordingly.

How to test for the presence of a macro in CMake?

To test for the presence of a macro in CMake, you can use the "CHECK_C_SOURCE_RUNS" command.

Here's an example of how you can test for the presence of a macro called "MY_MACRO":

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# Create a test source file that uses the macro
file(WRITE test.c "#include <stdio.h>\n#define MY_MACRO 1\nint main() { printf(\"%d\\n\", MY_MACRO); return 0; }")

# Check if the test source file compiles and runs
CHECK_C_SOURCE_RUNS("int main() { MY_MACRO; return 0; }" MY_MACRO_DEFINED)
if(MY_MACRO_DEFINED)
    message("Macro MY_MACRO is defined")
else()
    message("Macro MY_MACRO is not defined")
endif()

This code snippet creates a test source file that defines the macro "MY_MACRO", compiles and runs the source file, and then checks if the macro is defined during the compilation. The result is stored in the variable MY_MACRO_DEFINED, which is then used to determine if the macro is present.