Re: GCC nested functions?

[David Mosberger <davidm@napali.hpl.hp.com>]

>>>>> On Wed, 12 May 2004 10:59:24 -0700, Stephen Hemminger <shemminger@osdl.org> said:

  Stephen> I used GCC nested functions in the (not released) bridge
  Stephen> sysfs interface for 2.6.6.  It seemed like a nice way to
  Stephen> express the sysfs related interface without doing lots of
  Stephen> code copying (or worse lots of macros).

Oh, man!  Nested C functions are evil.  Just don't do it.

  Stephen> This works fine for GCC 2.95 and 3.X for i386 and x86_64
  Stephen> architectures, but the ia64 (cross compiler) pukes with:

  Stephen> In function `store_forward_delay':
  Stephen> : undefined reference to `__ia64_trampoline'

  Stephen> Redoing it as separate functions is easy enough, but the
  Stephen> questions are:

  Stephen> - Are gcc nested functions allowed in the kernel?  If not
  Stephen> where should this restriction be put in Documentation?
  Stephen> CodingStyles?

Nested C functions shouldn't be allowed _anywhere_.  It's the worst
extension that has made it into GNU C.

  Stephen> - Or is gcc on ia64 just too stupid? or do some more
  Stephen> support routines need to exist in arch/ia64?

It has nothing to do with stupidity.  The kernel doesn't support all
the routines provided by libgcc.a.  __ia64_trampoline() is one of
them.

  Stephen> - Do other architectures (sparc, ppc) have similar problems?

It's not a problem.  It's a feature.  It's likely that other
architectures which require a helper-routine from libgcc would behave
the same.

	--david