[vlc-devel] [PATCH] configure: check the C compiler needs -latomic to support atomics

[Steve Lhomme]

At least gcc 8 for the Raspberry Pi needs it.
---
 configure.ac | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/configure.ac b/configure.ac
index c2a2a231cee..a7cf39d2174 100644
--- a/configure.ac
+++ b/configure.ac
@@ -70,6 +70,23 @@ AC_C_INLINE
 AC_C_RESTRICT
 AX_CXX_COMPILE_STDCXX_14([noext], [mandatory])
 
+dnl Check the compiler supports atomics in C
+AC_MSG_CHECKING([C atomics])
+AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <stdatomic.h>],[
+atomic_uintmax_t test;
+atomic_init(&test, 0);
+atomic_fetch_add_explicit(&test, 2u, memory_order_relaxed);
+])], [AC_MSG_RESULT([built-in])], [
+  LDFLAGS="$LDFLAGS -latomic"
+  AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <stdatomic.h>],[
+atomic_uintmax_t test;
+atomic_init(&test, 0);
+atomic_fetch_add_explicit(&test, 2u, memory_order_relaxed);
+])],[AC_MSG_RESULT([using -latomic])],[
+  AC_MSG_ERROR([VLC requires atomics support])
+  ])
+])
+
 dnl Extend the --help string at the current spot.
 AC_DEFUN([EXTEND_HELP_STRING], [m4_divert_once([HELP_ENABLE], [$1])])
 
-- 
2.17.1