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macroscmakedefinitions

How to define a CMake macro in terms of another one?

How to define a CMake macro in terms of another one?

add_definitions(-DMACRO1=1)
add_definitions(-DMACRO2=2)

add_definitions(-DMACRO3=${MACRO1})   # no effect

message( "COMPILE_DEFINITIONS = ${DirDefs}" )

This is the output I would like:

COMPILE_DEFINITIONS = MACRO1=1;MACRO2=2;MACRO3=1

This is what I get:

COMPILE_DEFINITIONS = MACRO1=1;MACRO2=2;MACRO3=
Solution

  • Calling add_definitions(-DMACRO1=1) simply adds this definition to your compiler's command-line. Its value is equivalent to a #define directive in your source code. It does not create a CMake variable.

    So, in your case,${MACRO1} evaluates to the empty string, resulting in 

    ADD_DEFINITIONS(-DMACRO3=)

    To make it work, use SET(...) to define the variable in CMake:

    set(MACRO1 1)
add_definitions(-DMACRO1=${MACRO1})
add_definitions(-DMACRO2=2)

add_definitions(-DMACRO3=${MACRO1})

message( "COMPILE_DEFINITIONS = ${DirDefs}" )