How to define macro for C project in autotools?

How do I define macros on a per-pro开发者_运维百科ject, or per file level in a C project using autotools?

Presently I have this: mount_cpfs_CPPFLAGS = -DFUSE_USE_VERSION=28, but I'm not sure that this is the "portable" way to define a C macro.

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Consider using generated header files with AC_DEFINE.