zeromq: add libatomic linkage when available

Fixes:
http://autobuild.buildroot.net/results/ff5f7d3bcd713db9c9d92a746d6ad7134748fe16
http://autobuild.buildroot.net/results/9a743da1c3be673288c3482a9e7ddea12750206f
http://autobuild.buildroot.net/results/818b12387e6117569c4fab310b98c11fac80c047

If libatomic is available, it should be added to LIBS in CONF_ENV, since without it we can get into a state in which symbols like __atomic_fetch_sub_4, __atomic_compare_exchange_4 and __atomic_fetch_add_4 can't be found.

Signed-off-by Asaf Kahlon <[email protected]>

---
 package/zeromq/zeromq.mk | 4 ++++
 1 file changed, 4 insertions(+)

package/zeromq/zeromq.mk +0 -0

index 8273cad763..214bd9e35c 100644

Hello Asaf,

Quoted 2 lines · Asaf Kahlon

Fixes:

http://autobuild.buildroot.net/results/ff5f7d3bcd713db9c9d92a746d6ad7134748fe16

Quoted 1 line

http://autobuild.buildroot.net/results/9a743da1c3be673288c3482a9e7ddea12750206f

Quoted 1 line

http://autobuild.buildroot.net/results/818b12387e6117569c4fab310b98c11fac80c047

Quoted 2 lines

If libatomic is available, it should be added to LIBS in CONF_ENV, since

without

Quoted 13 lines

it we can get into a state in which symbols like __atomic_fetch_sub_4, __atomic_compare_exchange_4 and __atomic_fetch_add_4 can't be found.

Signed-off-by Asaf Kahlon <[email protected]>

---
 package/zeromq/zeromq.mk | 4 ++++
 1 file changed, 4 insertions(+)

package/zeromq/zeromq.mk +0 -0

index 8273cad763..214bd9e35c 100644

package/zeromq/zeromq.mk else · line 63

Quoted 6 lines

package/zeromq/zeromq.mk +3 -0

@@ -58,4 +58,8 @@ else
 ZEROMQ_CONF_OPTS += --disable-libunwind
 endif
 
+ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
+ZEROMQ_CONF_OPTS += LIBS=-latomic
+endif

While this does fix the problem, I don't think it's the most ideal fix. Indeed, the solution should be upstreamed. Currently, zeromq configure.ac uses LIBZMQ_CHECK_ATOMIC_INTRINSICS, which is implemented in acinclude.m4, to detect the availability of atomic intrinsics.

It goes like this:

AC_DEFUN([LIBZMQ_CHECK_ATOMIC_INTRINSICS], [{
AC_MSG_CHECKING(whether compiler supports __atomic_Xxx intrinsics) AC_COMPILE_IFELSE([AC_LANG_SOURCE([
/* atomic intrinsics test */
int v = 0;
int main (int, char **)

{
    int t = __atomic_add_fetch (&v, 1, __ATOMIC_ACQ_REL);
    return t;
}
    ])],
    [AC_MSG_RESULT(yes) ; libzmq_cv_has_atomic_instrisics="yes" ; $1],
    [AC_MSG_RESULT(no)  ; libzmq_cv_has_atomic_instrisics="no"  ; $2]
    )
}])

It does only an AC_COMPILE_IFELSE(), so it succeeds on Sparc, as the need for -latomic only appears at link time.

So I believe it should be changed to test with AC_LINK_IFELSE, and if it fails, test with AC_LINK_IFELSE with -latomic, to determine

(1) If atomic intrinsics are available

(2) If -latomic is needed to use atomic intrinsics

Do you think you could have a look at implementing something like this ?

That being said, I agree that a number of other packages in Buildroot are fixed by just passing LIBS=-latomic.

Best regards,

Thomas
--
Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering
https://bootlin.com

I completely agree that the solution should be on upstream, and the current solution is easiest one but not the best one. I'll try to build a patch on the upstream and send it here.