Heads up: OFED build by default

[Mark Millard]

OFED in head lead to the following in order for ci.freebsd.org's
FreeBSD-head-amd64-gcc builds to not fail/stop in
all_subdir_lib/ofed :

Author: jhb
Date: Mon Aug  6 23:51:08 2018
New Revision: 337399
URL: 
https://svnweb.freebsd.org/changeset/base/337399


Log:
  Make the system C11 atomics headers fully compatible with external GCC.
  
  The <sys/cdefs.h> and <stdatomic.h> headers already included support for
  C11 atomics via intrinsincs in modern versions of GCC, but these versions
  tried to "hide" atomic variables inside a wrapper structure.  This wrapper
  is not compatible with GCC's internal <stdatomic.h> header, so that if
  GCC's <stdatomic.h> was used together with <sys/cdefs.h>, use of C11
  atomics would fail to compile.  Fix this by not hiding atomic variables
  in a structure for modern versions of GCC.  The headers already avoid
  using a wrapper structure on clang.
  
  Note that this wrapper was only used if C11 was not enabled (e.g.
  via -std=c99), so this also fixes compile failures if a modern version
  of GCC was used with -std=c11 but with FreeBSD's <stdatomic.h> instead
  of GCC's <stdatomic.h> and this change fixes that case as well.
  
  Reported by:	Mark Millard
  Reviewed by:	kib
  Differential Revision:	
https://reviews.freebsd.org/D16585


Modified:
  head/sys/sys/cdefs.h
  head/sys/sys/stdatomic.h


Without this FreeBSD-head-amd64-gcc was getting:

--- all_subdir_lib/ofed ---
In file included from /workspace/src/contrib/ofed/librdmacm/cma.h:43:0,
                from /workspace/src/contrib/ofed/librdmacm/acm.c:42:
/workspace/src/contrib/ofed/librdmacm/cma.h: In function 'fastlock_init':
/workspace/src/contrib/ofed/librdmacm/cma.h:60:2: error: invalid initializer
 atomic_store(&lock->cnt, 0);
 ^
In file included from /workspace/src/contrib/ofed/librdmacm/acm.c:42:0:
/workspace/src/contrib/ofed/librdmacm/cma.h: In function 'fastlock_acquire':
/workspace/src/contrib/ofed/librdmacm/cma.h:68:2: error: operand type 'struct <anonymous> *' is incompatible with argument 1 of '__atomic_fetch_add'
 if (atomic_fetch_add(&lock->cnt, 1) > 0)
 ^~
/workspace/src/contrib/ofed/librdmacm/cma.h: In function 'fastlock_release':
/workspace/src/contrib/ofed/librdmacm/cma.h:73:2: error: operand type 'struct <anonymous> *' is incompatible with argument 1 of '__atomic_fetch_sub'
 if (atomic_fetch_sub(&lock->cnt, 1) > 1)
 ^~
. . .
--- all_subdir_lib/ofed ---
*** [acm.o] Error code 1


Side notes:

A modern enough /usr/ports avoids the devel/*-gcc
the separate float.h problem: -r476273 fixed
/devel/powerpc64-gcc (the master port for
devel/*-gcc ports) to avoid this.

With both fixes in place I was able to buildworld
buildkernel via amd64's xtoolchain ( so via its
use of devel/amd64-gcc ). (The build servers likely
do not have -r476273 yet.)


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)