CODEWITHSUNDEEP
cmake
feelfree
feelfree

Reputation: 11773

How to share variables between different CMake files

How do I share variables between different CMake files, and I show the following examples to illustrate my question:

Main

cmake_minimum_required(VERSION 2.6)
project(test)
set(Var3 "Global variable")

add_subdirectory(${test_SOURCE_DIR}/exe)
add_subdirectory(${test_SOURCE_DIR}/dll)

EXE file

set(Var1 "this is variable 1")
set(Var1 ${Var1} " added to varible 1")
message(STATUS ${Var1})

DLL file

set(Var2 "this is variable 2")
message(STATUS ${Var2})
message(STATUS ${Var1})
message(STATUS ${Var3})

In this example, Var3 can be seen in the CMake files of exe and dll as it is defined in Main. However, Var1, which is defined in exe, will not be observed in dll. I was just curious: is there a way to make Var1 defined in exe observable in dll?

Upvotes: 30

Views: 23053

Answers (3)

TheEagle
TheEagle

Reputation: 5980

In my case I was applying a list(TRANSFORM) on the variable, and these modifications were not reflected at global scope - apparently the list command only in-place-modifies the local variable, and not the global one - I used an intermediary variable as a workaround:

set(MOC_HEADERS
    application.hxx
    command.hxx
    menubar.hxx
    uiloader.hxx
)
list(TRANSFORM MOC_HEADERS PREPEND "${CMAKE_CURRENT_LIST_DIR}/")
set(EASYQT_MOC_HEADERS ${MOC_HEADERS} CACHE INTERNAL "")

Upvotes: 0

Antonio
Antonio

Reputation: 20326

Beside what Tadeusz correctly said, you can make a variable visible at any level (not just one up!) by using

set(Var1 "This is variable 1" CACHE INTERNAL "")

The variable will be available for all the CMake instructions that follow that instruction, so for example it won't be available for a sister directory that is added before the directory where this variable is defined.

Upvotes: 33

Tadeusz A. Kadłubowski
Tadeusz A. Kadłubowski

Reputation: 8363

The scopes of variable visibility form a tree. The CMakeFiles.txt files added with add_subdirectory have access to the variables defined in themselves, and in the parent scope (the toplevel global scope in your example).

You can export a variable one level up using:

set(Var1 "This is variable 1" PARENT_SCOPE)

Upvotes: 19

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