openal: fix atomic handling

	bool "openal"

	depends on BR2_INSTALL_LIBSTDCPP

	depends on BR2_TOOLCHAIN_HAS_THREADS_NPTL

	depends on BR2_PAKCAGE_OPENAL_ARCH_SUPPORTS

	select BR2_PACKAGE_OPENAL

comment "openal plugin needs a toolchain w/ NPTL, C++"

	depends on BR2_PAKCAGE_OPENAL_ARCH_SUPPORTS

	depends on !BR2_TOOLCHAIN_HAS_THREADS_NPTL \

		|| !BR2_INSTALL_LIBSTDCPP

From 10fee6d71a1f7d6e6319005196562b4a30b4e8ff Mon Sep 17 00:00:00 2001

From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Date: Tue, 2 Feb 2016 14:58:52 +0100

Subject: [PATCH] Fix detection of C11 atomics

Currently, the CMakeLists.txt logic to detect the availability of C11

atomics is based on building a small program that uses the

atomic_load().

However, atomic_load() does not need to use any function from

libatomic (part of the gcc runtime). So even if libatomic is missing,

this test concludes that C11 atomic support is available. For example

on SPARC, the example program builds fine without linking to

libatomic, but calling other functions of the atomic_*() APIs fail

without linking to libatomic.

So, this patch adjusts the CMakeLists.txt test to use a function that

is known to require the libatomic run-time library (on architectures

where it is needed). This way, openal will only use the __atomic_*()

built-ins when they are actually functional.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

---

 CMakeLists.txt | 7 +++++--

 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt

index 5784d35..a53f996 100644

--- a/CMakeLists.txt

+++ b/CMakeLists.txt

@@ -209,14 +209,17 @@ CHECK_C_SOURCE_COMPILES(

 HAVE_C11_ALIGNAS)

 # Check if we have C11 _Atomic

+set(OLD_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})

+set(CMAKE_REQUIRED_LIBRARIES ${EXTRA_LIBS})

 CHECK_C_SOURCE_COMPILES(

 "#include <stdatomic.h>

- const int _Atomic foo = ATOMIC_VAR_INIT(~0);

+ int _Atomic foo = ATOMIC_VAR_INIT(~0);

  int main()

  {

-     return atomic_load(&foo);

+     return atomic_fetch_add(&foo, 2);

  }"

 HAVE_C11_ATOMIC)

+set(CMAKE_REQUIRED_LIBRARIES ${OLD_REQUIRED_LIBRARIES})

 # Add definitions, compiler switches, etc.

 INCLUDE_DIRECTORIES("${OpenAL_SOURCE_DIR}/include" "${OpenAL_BINARY_DIR}")

-- 

2.6.4

# openal can:

# - use __atomic_*() intrinsics when available

# - otherwise use __sync_*() intrinsics when available. It needs the

#   4-byte ones on 32 bits architectures, and the 4-byte and 8-byte

#   one on 64 bits architecture

# - it also provides its one implementation of atomic operations on

#   x86 and x86_64, but we dont take those into account since in most

#   situations __atomic_*() or __sync_*() will be available, and not

#   all x86 CPUs provide the necessary assembly instructions.

config BR2_PACKAGE_OPENAL_ARCH_SUPPORTS

	bool

	default y if BR2_TOOLCHAIN_HAS_ATOMIC

	default y if BR2_TOOLCHAIN_HAS_SYNC_4 && !BR2_ARCH_IS_64

	default y if BR2_TOOLCHAIN_HAS_SYNC_4 && BR2_TOOLCHAIN_HAS_SYNC_8 && BR2_ARCH_IS_64

config BR2_PACKAGE_OPENAL

	bool "openal"

	depends on BR2_INSTALL_LIBSTDCPP

	depends on BR2_TOOLCHAIN_HAS_THREADS_NPTL

	depends on BR2_PACKAGE_OPENAL_ARCH_SUPPORTS

	help

	  OpenAL provides capabilities for playing audio in a virtual

	  3D environment. Distance attenuation, doppler shift, and

	  http://kcat.strangesoft.net/openal.html

comment "openal needs a toolchain w/ NPTL, C++"

	depends on BR2_PACKAGE_OPENAL_ARCH_SUPPORTS

	depends on !BR2_TOOLCHAIN_HAS_THREADS_NPTL \

		|| !BR2_INSTALL_LIBSTDCPP

# We don't need the utilities, Distros don't ship them either

OPENAL_CONF_OPTS += -DALSOFT_UTILS=OFF

ifeq ($(BR2_TOOLCHAIN_GCC_AT_LEAST_4_8),y)

OPENAL_CONF_OPTS += -DEXTRA_LIBS=atomic

endif

ifeq ($(BR2_PACKAGE_ALSA_LIB),y)

OPENAL_DEPENDENCIES += alsa-lib

OPENAL_CONF_OPTS += -DALSOFT_REQUIRE_ALSA=ON