# add_compile_options

Add options to the compilation of source files.

    add_compile_options(<option> ...)

Adds options to the `COMPILE_OPTIONS` directory property. These options are used when compiling targets from the current directory and below.

## Arguments

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 its 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`.

## Example

Since different compilers support different options, a typical use of this command is in a compiler-specific conditional clause:

    if (MSVC)
        # warning level 4 and all warnings as errors
        add_compile_options(/W4 /WX)
    else()
        # lots of warnings and all warnings as errors
        add_compile_options(-Wall -Wextra -pedantic -Werror)
    endif()

## See Also

This command can be used to add any options. However, for adding preprocessor definitions and include directories it is recommended to use the more specific commands `add_compile_definitions()` and `include_directories()`.

The command `target_compile_options()` adds target-specific options.

The source file property `COMPILE_OPTIONS` adds options to one source file.