Undefined symbols in libiperf when building for ARMv6

[jpalus]

Context

• Version of iperf3: 3.16

• Hardware: ARMv6

• Operating system (and distribution, if any): PLD Linux

Bug Report

• Expected Behavior

libiperf does not have unresolved symbols.

• Actual Behavior

libiperf has unresolved symbols related to 64-bit atomics:

	__atomic_store_8
	__atomic_load_8
	__atomic_fetch_add_8

• Steps to Reproduce

1. Compile iperf targetting ARMv6

• Possible Solution

Link libatomic

[bmah888]

Thanks for the issue and the PR!

[jpalus]

Just for reference sample reproducer with podman and alpine (feel free to replace with docker and your favorite 32-bit x86 distribution):

$ podman run --rm -i --arch i386 docker.io/alpine sh <<EOF
apk add gcc musl-dev make
cd /tmp
wget -O - https://github.com/esnet/iperf/releases/download/3.16/iperf-3.16.tar.gz | tar zxf -
cd iperf-3.16
./configure CFLAGS="-march=i386"
make -j$(nproc)
EOF

Gives:

...
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_store_8'
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_fetch_add_8'
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_load_8'
collect2: error: ld returned 1 exit status
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_store_8'
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_fetch_add_8'
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_load_8'
make[2]: *** [Makefile:893: t_uuid] Error 1
make[2]: *** Waiting for unfinished jobs....
collect2: error: ld returned 1 exit status
make[2]: *** [Makefile:869: iperf3] Error 1
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_store_8'
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_fetch_add_8'
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_load_8'
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_store_8'
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_fetch_add_8'
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_load_8'
collect2: error: ld returned 1 exit status
collect2: error: ld returned 1 exit status
make[2]: *** [Makefile:885: t_timer] Error 1
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_store_8'
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_fetch_add_8'
/usr/lib/gcc/i586-alpine-linux-musl/13.2.1/../../../../i586-alpine-linux-musl/bin/ld: ./.libs/libiperf.so: undefined reference to `__atomic_load_8'
make[2]: *** [Makefile:877: t_api] Error 1
collect2: error: ld returned 1 exit status
make[2]: *** [Makefile:889: t_units] Error 1
make[2]: Leaving directory '/tmp/iperf-3.16/src'
make[1]: Leaving directory '/tmp/iperf-3.16/src'
make[1]: *** [Makefile:720: all] Error 2
make: *** [Makefile:398: all-recursive] Error 1

Similarly with #1612 fix applied:

$ podman run --rm -i --arch i386 docker.io/alpine sh <<EOF
apk add gcc musl-dev make patch autoconf automake libtool
cd /tmp
wget -O - https://github.com/esnet/iperf/releases/download/3.16/iperf-3.16.tar.gz | tar zxf -
cd iperf-3.16
wget -O - https://github.com/esnet/iperf/pull/1612.patch | patch -p1
aclocal
autoconf
automake
./configure CFLAGS="-march=i386"
make -j$(nproc)
EOF

Builds fine.