meson.build: test for and link against libatomic if it exists

It's needed on some platforms for some subset (or all) atomic operations and
checking for the cases when it's actually needed is quite complex.

Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/4300

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8637>

subprojects/gst-plugins-bad/gst-libs/gst/cuda/meson.build

@@ -48,15 +48,12 @@ if host_system not in ['windows', 'linux']
   subdir_done()
 endif
 
-# Linux ARM would need -latomic for std::atomic<int64_t>
+# Check for libatomic for use of C11 atomics: some architectures need
-if host_system == 'linux' and host_machine.cpu_family() in ['aarch64', 'arm']
+# to link explicitly to this library.
-  libatomic_dep = cxx.find_library('atomic', required: get_option('cuda-nvmm'))
+# TODO: Once meson 1.7 is in use, this can be updated to
-  if not libatomic_dep.found()
+# dependency('atomic')
-    subdir_done()
+atomic_dep = cxx.find_library('atomic', required: false)
-  endif
+gstcuda_platform_dep += [atomic_dep]
-
-  gstcuda_platform_dep += [libatomic_dep]
-endif
 
 cuda_win32_headers = [
   'initguid.h',

subprojects/gst-plugins-base/gst-libs/gst/audio/meson.build

@@ -162,7 +162,7 @@ gstaudio = library('gstaudio-@0@'.format(api_version),
   soversion : soversion,
   darwin_versions : osxversion,
   install : true,
-  dependencies : gstaudio_deps,
+  dependencies : [ gstaudio_deps, base_platform_dep ],
 )
 pkg_name = 'gstreamer-audio-1.0'
 pkgconfig.generate(gstaudio,

subprojects/gst-plugins-base/meson.build

@@ -398,6 +398,15 @@ else
   core_conf.set('DISABLE_ORC', 1)
 endif
 
+base_platform_dep = []
+# Check for libatomic for use of C11 atomics: some architectures need
+# to link explicitly to this library.
+# TODO: Once meson 1.7 is in use, this can be updated to
+# dependency('atomic')
+atomic_dep = cc.find_library('atomic', required: false)
+
+base_platform_dep += [atomic_dep]
+
 # Used to build SSE* things in audio-resampler
 sse_args = '-msse'
 sse2_args = '-msse2'

subprojects/gstreamer/meson.build

@@ -599,6 +599,13 @@ if nsl_lib.found()
   network_deps += nsl_lib
 endif
 
+# Check for libatomic for use of C11 atomics: some architectures need
+# to link explicitly to this library.
+# TODO: Once meson 1.7 is in use, this can be updated to
+# dependency('atomic')
+atomic_dep = cc.find_library('atomic', required: false)
+platform_deps += atomic_dep
+
 gir = find_program('g-ir-scanner', required : get_option('introspection'))
 gnome = import('gnome')