何時觸發cmakes add_custom_command POST_BUILD？

Question

讓我們考慮，我已經註冊了一個自定義命令的目標：

add_custom_command(TARGET ${target_name} POST_BUILD 
        COMMAND cmake -E copy_if_different ${file_path} ${dest_file} 
        COMMENT "exporting ${file_path} to ${dest_file}" 
        VERBATIM) 

我很努力找出當命令實際上是正在運行的。 目標檢查後總是這樣嗎？

[ 10%] Built target libzmq 

即使'什麼也沒做'？

或者只是爲了防止目標事情發生？

Answer 1

Documentation：

The command becomes part of the target and will only execute when the 
target itself is built. If the target is already built, the command will 
not execute.