# add_compile_options

Adds options to the compilation of source files.

    add_compile_options(<option> ...)

Adds options to the compiler command line for targets in the current directory and below that are added after this command is invoked. See documentation of the `directory` and `target` `COMPILE_OPTIONS` properties.

This command can be used to add any options, but alternative commands exist to add preprocessor definitions (`target_compile_definitions()` and `add_compile_definitions()`) or include directories (`target_include_directories()` and `include_directories()`).

Arguments to `add_compile_options` may use “generator expressions” with the syntax `$<...>`. See the `cmake-generator-expressions(7)` manual for available expressions. See the `cmake-buildsystem(7)` manual for more on defining buildsystem properties.

The final set of compile or link options used for a target is constructed by accumulating options from the current target and the usage requirements of it dependencies. The set of options is de-duplicated to avoid repetition. While beneficial for individual options, the de-duplication step can break up option groups. For example, `-D A -D B` becomes `-D A B`. One may specify a group of options using shell-like quoting along with a `SHELL:` prefix. The `SHELL:` prefix is dropped and the rest of the option string is parsed using the `separate_arguments()` `UNIX_COMMAND` mode. For example, `"SHELL:-D A" "SHELL:-D B"` becomes `-D A -D B`.