TOOL_DEPENDS vs. BUILD_DEPENDS

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

Do I understand this correctly:

The difference between TOOL_DEPENDS and BUILD_DEPENDS only matters
when you are cross-building packages for a different architecture.

TOOL_DEPENDS are programs that need to be run on the build system when
building the package. So they must match the architecture of the
system on which the package is built.

BUILD_DEPENDS are dependencies that are only needed at build time, but
must match the architecture of the target system (not the build system).

I think pkgsrc mostly uses BUILD_DEPENDS since cross-building was only
added later and before that, there was no difference between the too.

In general, most BUILD_DEPENDS should probably be TOOL_DEPENDS
instead. I can't think of a good example for a BUILD_DEPENDS, but
there must be one, somewhere :)

Is this correct?

What are good examples for BUILD_DEPENDS?

Can someone think of tests that could be added to pkglint for this?
 Thomas