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From 95e601ce116dd46ea7915c171976b85ea0905d58 Mon Sep 17 00:00:00 2001
From: Lonnie Abelbeck <lonnie@abelbeck.com>
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 <raj.khem@gmail.com>
---
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 <stdint.h>
+ 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
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