DEPENDENCIES_OUTPUT misdocumented?

[Jamie Lokier <egcs at tantalophile dot demon dot co dot uk>]

DEPENDENCIES_OUTPUT is documented as having a similar effect to -M.
I.e., it makes a file containing system and user header dependencies.

  @item DEPENDENCIES_OUTPUT
  @findex DEPENDENCIES_OUTPUT
  @cindex dependencies for make as output
  If this variable is set, its value specifies how to output dependencies
  for Make based on the header files processed by the compiler.  This
  output looks much like the output from the @samp{-M} option
  (@pxref{Preprocessor Options}), but it goes to a separate file, and is
  in addition to the usual results of compilation.

But I just tried GCC 2.95.2 and it produced only the user header files.
A quick glance at cppinit.c from the recent snapshot indicates that's
still how it is.

Now, IMO this is rather useful behaviour.

But is it a documentation or a coding bug?

While we're here, why is SUNPRO_DEPENDENCIES not documented?
Occasionally it's rather useful, and there is no other equivalent set of
options.

thanks,
-- Jamie