Re: [PATCH] arm: do not abort EABI check for bootstrapping

[Joseph Myers <joseph at codesourcery dot com>]

On Thu, 20 Nov 2014, Roland McGrath wrote:

> That's not necessarily always true, though probably it is in practice and
> perhaps it should be by policy.  That is, nowadays we use compiler-based
> checks (checking predefines) in some places to contribute to the sysdeps
> directory selection.  It could be that which installed sysdeps headers you
> get is affected by sysdeps directory choices that were affected by
> compiler-based configure checks.  The only checks of this sort I can think
> of off hand are for "submodel" sorts of variation, and for x32 (choosing
> between ABIs in a tri-arch ABI setup); those are cases where we intend the
> installed headers to be universal across the submodels and across the
> cooperating ABI sets.  But nothing in the infrastructure ensures that there
> cannot be a case where it matters, and I'm not entirely confident off hand
> that as a matter of policy we always do or should rule out all such cases.

There are some cases where submodel variation does affect the installed 
headers.  At least:

* m68k bits/fenv.h and bits/mathinline.h.

* sh bits/mathdef.h.

(I think these should be fixed.)

There are other cases where it may look like submodel variation could 
affect the headers but actually the variants in different sysdeps 
directories are identical (e.g. sysdeps/s390/s390-32/bits/wordsize.h and 
sysdeps/s390/s390-64/bits/wordsize.h - which exist because of the sysdeps 
directory ordering issue described in 
<https://sourceware.org/ml/libc-alpha/2014-03/msg00588.html>).

-- 
Joseph S. Myers
joseph@codesourcery.com