From 95e601ce116dd46ea7915c171976b85ea0905d58 Mon Sep 17 00:00:00 2001 From: Lonnie Abelbeck Date: Sun, 8 May 2022 14:05:56 -0500 Subject: [PATCH] configure.ac: Link with -latomic only if no atomic builtins Follow-up to 561dbda, a check of GCC atomic builtins needs to be done first. I'm no autoconf guru, but using this: https://github.com/mesa3d/mesa/blob/0df485c285b73c34ba9062f0c27e55c3c702930d/configure.ac#L469 as inspiration, I created a pre-check before calling AC_SEARCH_LIBS(...) Fixes #1135 Closes #1139 Upstream-Status: Backport [https://github.com/kraj/libusb/commit/95e601ce116dd46ea7915c171976b85ea0905d58] Signed-off-by: Khem Raj --- configure.ac | 16 +++++++++++++++- libusb/version_nano.h | 2 +- 2 files changed, 16 insertions(+), 2 deletions(-) --- a/configure.ac +++ b/configure.ac @@ -153,7 +153,21 @@ if test "x$platform" = xposix; then AC_SEARCH_LIBS([pthread_create], [pthread], [test "x$ac_cv_search_pthread_create" != "xnone required" && AC_SUBST(THREAD_LIBS, [-lpthread])], [], []) - AC_SEARCH_LIBS([__atomic_fetch_add_4], [atomic]) + dnl Check for new-style atomic builtins. We first check without linking to -latomic. + AC_MSG_CHECKING(whether __atomic_load_n is supported) + AC_LINK_IFELSE([AC_LANG_SOURCE([[ + #include + int main() { + struct { + uint64_t *v; + } x; + return (int)__atomic_load_n(x.v, __ATOMIC_ACQUIRE) & + (int)__atomic_add_fetch(x.v, (uint64_t)1, __ATOMIC_ACQ_REL); + }]])], GCC_ATOMIC_BUILTINS_SUPPORTED=yes, GCC_ATOMIC_BUILTINS_SUPPORTED=no) + AC_MSG_RESULT($GCC_ATOMIC_BUILTINS_SUPPORTED) + if test "x$GCC_ATOMIC_BUILTINS_SUPPORTED" != xyes; then + AC_SEARCH_LIBS([__atomic_fetch_add_4], [atomic]) + fi elif test "x$platform" = xwindows; then AC_DEFINE([PLATFORM_WINDOWS], [1], [Define to 1 if compiling for a Windows platform.]) else