How do you concatenate string in cmake

Is there a way to concatenate strings in cmake?

I have a folder that only contains .cpp files with main methods. I thought this would be easy by just using a foreach through all src files. This is what I've got this far:

project(opengl-tutorial)
cmake_minimum_required(VERSION 2.8)

aux_source_directory(. SRC_LIST)

add_definitions(
    --std=c++11
)

foreach (src ${SRC_LIST})
    # name = ${src} + ".out"
    add_executable(${name} ${src})
    target_link_libraries(${name} GL GLU GLEW glfw)
endforeach(src ${SRC_LIST})

How can I do what's described in the comment?

Solution 1:

"${src}.out" should work fine, so you can write set(NAME "${src}.out") and use ${NAME} wherever you need to.

Solution 2:

Three typical CMake string concatenation methods

While the answer to this particular question will be best handled via set or string, there is a third possibility which is list if you want to join strings with an arbitrary character.

set()

Just combine strings like in bash

set(FILE file)
set(FILE_TXT ${FILE}.txt)
message(STATUS "FILE_TXT: ${FILE_TXT}")

string(CONCAT)

Concatenate all the input arguments together and store the result in the named output variable.

string(CONCAT [...])

string(CONCAT MULTI "xxxx" "YYYY" "xxxx")
message(STATUS "MULTI: ${MULTI}")

list(APPEND)

Appends elements to the list.

list(APPEND [ ...])

When it comes to things like compiler flags, this is the tool of choice. Lists in CMake are just semicolon separated strings and when you quote them, you get the list joined with semicolons.

list(APPEND FLAGS "-D option1")
list(APPEND FLAGS "-D option2")
list(APPEND FLAGS "-D option3")
list(JOIN FLAGS " " FLAGS)
message(STATUS "FLAGS: " ${FLAGS})

Solution 3:

if you just want to deal with a string value see @nonexplosive's answer.

However if you wish to have a Cmake variable in your CMakeLists.txt and set that variable to some value do use either: [string()] for Cmake 3.0+ (https://cmake.org/cmake/help/v3.0/command/string.html) or set() for Cmake 2.0+.

The reason you have two options is because older cmake doesn't support the CONCAT feature.

Example CMakeLists.txt:

cmake_minimum_required(VERSION 2.8.11)
project(Hello)
string(CONCAT x "hello" "goodbye")
set(y "hellogoodbye")
message(STATUS "DEBUG: x=${x}")
message(STATUS "DEBUG: y=${y}")

Full stdout:

-- DEBUG: x=hellogoodbye
-- DEBUG: y=hellogoodbye
-- Configuring done
-- Generating done
-- Build files have been written to: /home/_______/testing/_______