BUILD: makefile: simplify detection of libatomic
We've had libatomic enabled on arm and aarch64 for some Raspberry PI
while usually it's not needed, but it was a bit arbitrary and in
issue #1455 it was reported that RISCV requires it for single-byte
atomics.
This changes the approach to detect the explicit requirement of
external functions for the builtins, as reported with *_LOCK_FREE=1.
If any of the atomics requires libatomic, it will be used. Older
compilers do not report any such atomic as they use sync_* instead
and will not match it nor include libatomic (which usually is not
present there).
On x86, the rules depend on -march. i386 uses LOCK_FREE=1 for all of
them. i486 uses it only for the 8-byte CAS and i586 doesn't require
it at all. For this reason, the build flags are used during the test.
This was tested with armv7, aarch64, mips, riscv, i
diff --git a/Makefile b/Makefile
index 50a21b3..f5dfed2 100644
--- a/Makefile
+++ b/Makefile
@@ -54,6 +54,7 @@
# USE_THREAD_DUMP : use the more advanced thread state dump system. Automatic.
# USE_OT : enable the OpenTracing filter
# USE_MEMORY_PROFILING : enable the memory profiler. Linux-glibc only.
+# USE_LIBATOMIC : force to link with/without libatomic. Automatic.
#
# Options can be forced by specifying "USE_xxx=1" or can be disabled by using
# "USE_xxx=" (empty string). The list of enabled and disabled options for a
@@ -334,9 +335,6 @@
USE_SLZ = default
endif
-# Always enable threads support by default and let the Makefile detect if
-# HAProxy can be compiled with threads or not.
-
# generic system target has nothing specific
ifeq ($(TARGET),generic)
set_target_defaults = $(call default_opts,USE_POLL USE_TPROXY)
@@ -355,9 +353,6 @@
USE_CPU_AFFINITY USE_THREAD USE_EPOLL USE_LINUX_TPROXY \
USE_ACCEPT4 USE_LINUX_SPLICE USE_PRCTL USE_THREAD_DUMP USE_NS USE_TFO \
USE_GETADDRINFO USE_BACKTRACE)
-ifneq ($(shell echo __arm__/__aarch64__ | $(CC) -E -xc - | grep '^[^\#]'),__arm__/__aarch64__)
- TARGET_LDFLAGS=-latomic
-endif
endif
# For linux >= 2.6.28, glibc without new features
@@ -375,9 +370,6 @@
USE_CPU_AFFINITY USE_THREAD USE_EPOLL USE_LINUX_TPROXY \
USE_ACCEPT4 USE_LINUX_SPLICE USE_PRCTL USE_THREAD_DUMP USE_NS USE_TFO \
USE_GETADDRINFO)
-ifneq ($(shell echo __arm__/__aarch64__ | $(CC) -E -xc - | grep '^[^\#]'),__arm__/__aarch64__)
- TARGET_LDFLAGS=-latomic
-endif
endif
# Solaris 10 and above
@@ -460,6 +452,18 @@
# set the default settings according to the target above
$(set_target_defaults)
+# Some architectures require to link with libatomic for atomics of certain
+# sizes. These ones are reported as value 1 in the *_LOCK_FREE macros. Value
+# 2 indicates that the builtin is native thus doesn't require libatomic. Hence
+# any occurrence of 1 indicates libatomic is necessary. It's better to avoid
+# linking with it by default as it's not always available nor deployed
+# (especially on archs which do not need it).
+ifneq ($(USE_THREAD),)
+ifneq ($(shell $(CC) $(CFLAGS) -dM -E -xc - </dev/null 2>/dev/null | grep -c 'LOCK_FREE.*1'),0)
+ USE_LIBATOMIC=1
+endif
+endif
+
#### Determine version, sub-version and release date.
# If GIT is found, and IGNOREGIT is not set, VERSION, SUBVERS and VERDATE are
# extracted from the last commit. Otherwise, use the contents of the files
@@ -794,6 +798,10 @@
include addons/ot/Makefile
endif
+ifneq ($(USE_LIBATOMIC),)
+ TARGET_LDFLAGS += -latomic
+endif
+
#### Global link options
# These options are added at the end of the "ld" command line. Use LDFLAGS to
# add options at the beginning of the "ld" command line if needed.