package/libunwind/0002-Add-AO_REQUIRE_CAS-to-fix-build-on-ARM-v6.patch

   1 From 24484e80b3e329c9edee1995e102f8612eedb79c Mon Sep 17 00:00:00 2001
   2 From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
   3 Date: Tue, 13 May 2014 23:32:27 +0200
   4 Subject: [PATCH] Add AO_REQUIRE_CAS to fix build on ARM < v6
   5
   6 ARM earlier than ARMv6, such as ARMv4 and ARMv5 do not provide
   7 optimize atomic operations in libatomic_ops. Since libunwind is using
   8 such operations, it should define AO_REQUIRE_CAS before including
   9 <atomic_ops.h> so that libatomic_ops knows it should use emulated
  10 atomic operations instead (even though they are obviously a lot more
  11 expensive).
  12
  13 Also, while real atomic operations are all inline functions and
  14 therefore linking against libatomic_ops was not required, the emulated
  15 atomic operations actually require linking against libatomic_ops, so
  16 the commented AC_CHECK_LIB test in acinclude.m4 is uncommented to make
  17 sure we link against libatomic_ops.
  18
  19 Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
  20 ---
  21  acinclude.m4          | 8 +-------
  22  include/libunwind_i.h | 1 +
  23  2 files changed, 2 insertions(+), 7 deletions(-)
  24
  25 diff --git a/acinclude.m4 b/acinclude.m4
  26 index 497f7c2..9c15af1 100644
  27 --- a/acinclude.m4
  28 +++ b/acinclude.m4
  29 @@ -22,11 +22,5 @@ fi])
  30  AC_DEFUN([CHECK_ATOMIC_OPS],
  31  [dnl Check whether the system has the atomic_ops package installed.
  32    AC_CHECK_HEADERS(atomic_ops.h)
  33 -#
  34 -# Don't link against libatomic_ops for now.  We don't want libunwind
  35 -# to depend on libatomic_ops.so.  Fortunately, none of the platforms
  36 -# we care about so far need libatomic_ops.a (everything is done via
  37 -# inline macros).
  38 -#
  39 -#  AC_CHECK_LIB(atomic_ops, main)
  40 +  AC_CHECK_LIB(atomic_ops, main)
  41  ])
  42 diff --git a/include/libunwind_i.h b/include/libunwind_i.h
  43 index 23f615e..deabdfd 100644
  44 --- a/include/libunwind_i.h
  45 +++ b/include/libunwind_i.h
  46 @@ -95,6 +95,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
  47         (pthread_mutex_unlock != NULL ? pthread_mutex_unlock (l) : 0)
  48
  49  #ifdef HAVE_ATOMIC_OPS_H
  50 +# define AO_REQUIRE_CAS
  51  # include <atomic_ops.h>
  52  static inline int
  53  cmpxchg_ptr (void *addr, void *old, void *new)
  54 --
  55 1.9.2
  56