From 2ef7f23820a67e958c2252bd81eb0458903ebf33 Mon Sep 17 00:00:00 2001 From: Grazvydas Ignotas Date: Mon, 18 Sep 2017 22:11:26 +0300 Subject: [PATCH] configure: check if -latomic is needed for __atomic_* On some platforms, gcc generates library calls when __atomic_* functions are used, but does not link the required library (libatomic) automatically (supposedly to allow the app to use some other atomics implementation?). Detect this at configure time and add the library when needed. Tested on armel (library was added) and on x86_64 (was not, as expected). Some documentation on this is provided in GCC wiki: https://gcc.gnu.org/wiki/Atomic/GCCMM Fixes: 8915f0c0 "util: use GCC atomic intrinsics with explicit memory model" Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102573 Signed-off-by: Grazvydas Ignotas Reviewed-by: Matt Turner Reviewed-by: Emil Velikov --- configure.ac | 13 +++++++++++++ src/util/Makefile.am | 3 ++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/configure.ac b/configure.ac index f5d960f..d87b767 100644 --- a/configure.ac +++ b/configure.ac @@ -379,8 +379,21 @@ int main() { }]])], GCC_ATOMIC_BUILTINS_SUPPORTED=1) if test "x$GCC_ATOMIC_BUILTINS_SUPPORTED" = x1; then DEFINES="$DEFINES -DUSE_GCC_ATOMIC_BUILTINS" + dnl On some platforms, new-style atomics need a helper library + AC_MSG_CHECKING(whether -latomic is needed) + AC_LINK_IFELSE([AC_LANG_SOURCE([[ + #include + uint64_t v; + int main() { + return (int)__atomic_load_n(&v, __ATOMIC_ACQUIRE); + }]])], GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC=no, GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC=yes) + AC_MSG_RESULT($GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC) + if test "x$GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC" = xyes; then + LIBATOMIC_LIBS="-latomic" + fi fi AM_CONDITIONAL([GCC_ATOMIC_BUILTINS_SUPPORTED], [test x$GCC_ATOMIC_BUILTINS_SUPPORTED = x1]) +AC_SUBST([LIBATOMIC_LIBS]) dnl Check if host supports 64-bit atomics dnl note that lack of support usually results in link (not compile) error diff --git a/src/util/Makefile.am b/src/util/Makefile.am index 9885bbe..c37afff 100644 --- a/src/util/Makefile.am +++ b/src/util/Makefile.am @@ -48,7 +48,8 @@ libmesautil_la_SOURCES = \ libmesautil_la_LIBADD = \ $(CLOCK_LIB) \ - $(ZLIB_LIBS) + $(ZLIB_LIBS) \ + $(LIBATOMIC_LIBS) libxmlconfig_la_SOURCES = $(XMLCONFIG_FILES) libxmlconfig_la_CFLAGS = \ -- 2.7.4