Compilation fails on gcc 11 and gcc 10

[voltbit]

Hello, the project fails to build with the following output:

cd src && make all
make[1]: Entering directory '/tmp/redis-proxy/src'
Makefile:175: warning: overriding recipe for target '.make-prerequisites'
Makefile:161: warning: ignoring old recipe for target '.make-prerequisites'
    CC Makefile.dep
Makefile:175: warning: overriding recipe for target '.make-prerequisites'
Makefile:161: warning: ignoring old recipe for target '.make-prerequisites'
rm -rf redis-cluster-proxy *.o *.gcda *.gcno *.gcov lcov-html Makefile.dep
(cd ../deps && make distclean)
make[2]: Entering directory '/tmp/redis-proxy/deps'
(cd hiredis && make clean) > /dev/null || true
(rm -f .make-*)
make[2]: Leaving directory '/tmp/redis-proxy/deps'
(rm -f .make-*)
echo STD=-std=c11 -pedantic -DREDIS_STATIC='' >> .make-settings
echo WARN=-Wall -W -Wno-missing-field-initializers -Wno-format-security >> .make-settings
echo OPT=-O2 >> .make-settings
echo MALLOC=libc >> .make-settings
echo CFLAGS= >> .make-settings
echo LDFLAGS= >> .make-settings
echo REDIS_CLUSTER_PROXY_CFLAGS= >> .make-settings
echo REDIS_CLUSTER_PROXY_LDFLAGS= >> .make-settings
echo PREV_FINAL_CFLAGS=-std=c11 -pedantic -DREDIS_STATIC='' -Wall -W -Wno-missing-field-initializers -Wno-format-security -O2 -g -ggdb   -I../deps/hiredis >> .make-settings
echo PREV_FINAL_LDFLAGS=  -g -ggdb -rdynamic >> .make-settings
(cd ../deps && make hiredis)
make[2]: Entering directory '/tmp/redis-proxy/deps'
(cd hiredis && make clean) > /dev/null || true
(rm -f .make-*)
(echo "" > .make-cflags)
(echo "" > .make-ldflags)
MAKE hiredis
cd hiredis && make static
make[3]: Entering directory '/tmp/redis-proxy/deps/hiredis'
cc -std=c11 -pedantic -c -O3 -fPIC   -Wall -W -Wstrict-prototypes -Wwrite-strings -g -ggdb net.c
cc -std=c11 -pedantic -c -O3 -fPIC   -Wall -W -Wstrict-prototypes -Wwrite-strings -g -ggdb hiredis.c
cc -std=c11 -pedantic -c -O3 -fPIC   -Wall -W -Wstrict-prototypes -Wwrite-strings -g -ggdb sds.c
cc -std=c11 -pedantic -c -O3 -fPIC   -Wall -W -Wstrict-prototypes -Wwrite-strings -g -ggdb async.c
cc -std=c11 -pedantic -c -O3 -fPIC   -Wall -W -Wstrict-prototypes -Wwrite-strings -g -ggdb read.c
ar rcs libhiredis.a net.o hiredis.o sds.o async.o read.o
make[3]: Leaving directory '/tmp/redis-proxy/deps/hiredis'
make[2]: Leaving directory '/tmp/redis-proxy/deps'
    CC adlist.o
    CC ae.o
    CC anet.o
    CC cluster.o
cluster.c: In function ‘clusterNodeAuth’:
cluster.c:994:19: warning: ‘strncpy’ output truncated before terminating nul copying 26 bytes from a string of the same length [-Wstringop-truncation]
  994 |         if (*err) strncpy(*err, errmsg, errlen);
      |                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    CC commands.o
    CC config.o
    CC crc16.o
    CC debug.o
debug.c: In function ‘_proxyAssert’:
debug.c:784:18: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
  784 |     *((char*)-1) = 'x';
      |     ~~~~~~~~~~~~~^~~~~
    CC dict.o
    CC endianconv.o
    CC help.o
    CC logger.o
    CC memtest.o
    CC protocol.o
    CC proxy.o
In file included from proxy.c:21:
proxy.c: In function ‘mergeReplies’:
logger.h:38:28: warning: ‘%s’ directive argument is null [-Wformat-overflow=]
   38 | #define proxyLogDebug(...) proxyLog(LOGLEVEL_DEBUG, __VA_ARGS__)
      |                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
proxy.c:1215:17: note: in expansion of macro ‘proxyLogDebug’
 1215 |                 proxyLogDebug("Child reply:\n%s\np:\n%s\nendl:\n%s",
      |                 ^~~~~~~~~~~~~
proxy.c:1215:65: note: format string is defined here
 1215 |                 proxyLogDebug("Child reply:\n%s\np:\n%s\nendl:\n%s",
      |                                                                 ^~
proxy.c: In function ‘proxyCommand’:
proxy.c:1096:61: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
 1096 |         if (strcasecmp("segfault", type) == 0) *((char*)-1) = 'x';
      |                                                ~~~~~~~~~~~~~^~~~~
    CC rax.o
    CC release.o
    CC reply_order.o
    CC siphash.o
    CC sds.o
    CC util.o
    CC zmalloc.o
    LINK redis-cluster-proxy
/usr/bin/ld: logger.o:/tmp/redis-proxy/src/sds.h:37: multiple definition of `SDS_NOINIT'; config.o:/tmp/redis-proxy/src/sds.h:37: first defined here
/usr/bin/ld: reply_order.o:/tmp/redis-proxy/src/sds.h:37: multiple definition of `SDS_NOINIT'; config.o:/tmp/redis-proxy/src/sds.h:37: first defined here
/usr/bin/ld: sds.o:/tmp/redis-proxy/src/sds.h:37: multiple definition of `SDS_NOINIT'; config.o:/tmp/redis-proxy/src/sds.h:37: first defined here
/usr/bin/ld: util.o:/tmp/redis-proxy/src/sds.h:37: multiple definition of `SDS_NOINIT'; config.o:/tmp/redis-proxy/src/sds.h:37: first defined here
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:179: redis-cluster-proxy] Error 1
make[1]: Leaving directory '/tmp/redis-proxy/src'
make: *** [Makefile:4: all] Error 2

Build environments:

gcc (GCC) 11.1.0
Linux 5.10.61-1-MANJARO

and

alpine linux 3.14
10.3.1_git20210424-r2

See:
https://bugs.gentoo.org/707210
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=957751
redis/redis#6691