w32-short-file-name: multi-OS user-configuration — silence byte-compiler

Question

I have a multi-OS user-configuration. On OSX, when I byte-compile, the function w32-short-file-name is not defined (which is okay). What is the proper way to silence the byte-compiler for this message which will not affect the ability to use this user-configuration on Windows?

In end of data:
lawlist-dired.el:13754:1:Warning: the following functions are not known to be defined:
  w32-using-nt (3046),
  w32-short-file-name (370674)

[I am assuming I can apply the same answer to w32-using-nt.]

Answer 1

You can use declare-function to declare the files where the functions are defined. From C-hfdeclare-functionRET.

Tell the byte-compiler that function FN is defined, in FILE. Optional ARGLIST is the argument list used by the function. The FILE argument is not used by the byte-compiler, but by the ‘check-declare’ package, which checks that FILE contains a definition for FN. ARGLIST is used by both the byte-compiler and ‘check-declare’ to check for consistency.