Re: custom-add-loads: looking for clues

I'm trying to understand the (XEmacs) custom-add-loads function, as well as the custom-load.el file that gets generated for each package as part of the XEmacs package build. Can someone give me some clues or point me at some documentation? The reason I ask is that with MH-E 7, the generated custom-load.el contains (autoload 'custom-add-loads "cus-load") (custom-add-loads 'mh-identity '("mh-customize")) (custom-add-loads 'mh-speed-faces '("mh-customize")) (custom-add-loads 'mh-index-faces '("mh-customize")) (custom-add-loads 'mail '("mh-customize")) (custom-add-loads 'mh-alias '("mh-customize")) (custom-add-loads 'mh-speed '("mh-customize")) ... The custom-load.el that gets generated for MH-E 8.0.3 just has the autoload--there are no calls to custom-add-loads.

Is there some tag that needs to be present in the source file for the custom-add-loads call to be generated? There *is* an mh-cus-load.el in the MH-E 8.0.3 tarball (i.e., from upstream) that has (put 'mh-hooks 'custom-loads '("mh-e")) (put 'mh-sending-mail 'custom-loads '("mh-e")) (put 'mh-sequences 'custom-loads '("mh-e")) (put 'mh-junk 'custom-loads '("mh-e")) (put 'mh-thread 'custom-loads '("mh-e")) (put 'mh-search 'custom-loads '("mh-e")) ... but I can't tell if it's specific to GNU Emacs. Anyone know?