# COMPILE_DEFINITIONS

Added in version 4.4.

Preprocessor definitions for compiling a source file.

The `COMPILE_DEFINITIONS` property may be set to a semicolon-separated list of preprocessor definitions using the syntax `VAR` or `VAR=value`. Function-style definitions are not supported. CMake will automatically escape the value correctly for the native build system (note that CMake language syntax may require escapes to specify some values).

CMake will automatically drop some definitions that are not supported by the native build tool. `Xcode` does not support per-configuration definitions on source files.

Disclaimer: Most native build tools have poor support for escaping certain values. CMake has work-arounds for many cases but some values may just not be possible to pass correctly. If a value does not seem to be escaped correctly, do not attempt to work-around the problem by adding escape sequences to the value. Your work-around may break in a future version of CMake that has improved escape support. Instead consider defining the macro in a (configured) header file. Then report the limitation. Known limitations include:

> `#` | Broken almost everywhere.
> `;` | Broken in VS IDE 7.0 and Borland Makefiles.
> `,` | Broken in VS IDE.
> `%` | Broken in some cases in NMake.
> `& |` | Broken in some cases on MinGW.
> `^ < > \ "` | Broken in most Make tools on Windows.

CMake does not reject these values outright because they do work in some cases. Use with caution.

Contents of `COMPILE_DEFINITIONS` may use `cmake-generator-expressions(7)` with the syntax `$<...>`. See the `cmake-generator-expressions(7)` manual for available expressions. However, `Xcode` does not support per-config per-source settings, so expressions that depend on the build configuration are not allowed with that generator.

Related properties:

- Use `COMPILE_OPTIONS` to pass additional compile flags.

- Use `INCLUDE_DIRECTORIES` to pass additional include directories.

Related commands:

- `add_compile_definitions()` for directory-wide settings

- `target_compile_definitions()` for target-specific settings

- `set_source_files_properties()` for source-specific settings