error: passing an object that undergoes default argument promotion to 'va_start' has undefined behavior [-Werror,-Wvarargs]

Hi,i have issue with your source code libdatovka. I compiled on my FreeBSD 13.1 and clang

FreeBSD clang version 13.0.0 (git@github.com:llvm/llvm-project.git llvmorg-13.0.0-0-gd7b669b3a303)
Target: x86_64-unknown-freebsd13.1
Thread model: posix
InstalledDir: /usr/bin

gmake[3]: Entering directory '/media/ST3000DM007-1WY10G_ZTT0SM4Q_p1/code/FreeBSD-Ports/libdatovka/work/libdatovka-0.2.1/src'
/bin/sh ../libtool  --tag=CC   --mode=compile cc -DHAVE_CONFIG_H -I. -I..  -I/usr/local/include/libxml2 -I/usr/local/include -DLOCALEDIR=\"/usr/local/share/locale\" -I../include -isystem /usr/local/include -I/usr/local/include -I/usr/local/include -I/usr/local/include -O2 -pipe -I/usr/local/include -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing  -Werror -std=c99 -Wall -MT libdatovka_la-cdecode.lo -MD -MP -MF .deps/libdatovka_la-cdecode.Tpo -c -o libdatovka_la-cdecode.lo `test -f 'cdecode.c' || echo './'`cdecode.c
libtool: compile:  cc -DHAVE_CONFIG_H -I. -I.. -I/usr/local/include/libxml2 -I/usr/local/include -DLOCALEDIR=\"/usr/local/share/locale\" -I../include -isystem /usr/local/include -I/usr/local/include -I/usr/local/include -I/usr/local/include -O2 -pipe -I/usr/local/include -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing -Werror -std=c99 -Wall -MT libdatovka_la-cdecode.lo -MD -MP -MF .deps/libdatovka_la-cdecode.Tpo -c cdecode.c  -fPIC -DPIC -o .libs/libdatovka_la-cdecode.o
libtool: compile:  cc -DHAVE_CONFIG_H -I. -I.. -I/usr/local/include/libxml2 -I/usr/local/include -DLOCALEDIR=\"/usr/local/share/locale\" -I../include -isystem /usr/local/include -I/usr/local/include -I/usr/local/include -I/usr/local/include -O2 -pipe -I/usr/local/include -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing -Werror -std=c99 -Wall -MT libdatovka_la-cdecode.lo -MD -MP -MF .deps/libdatovka_la-cdecode.Tpo -c cdecode.c -o libdatovka_la-cdecode.o >/dev/null 2>&1
mv -f .deps/libdatovka_la-cdecode.Tpo .deps/libdatovka_la-cdecode.Plo
/bin/sh ../libtool  --tag=CC   --mode=compile cc -DHAVE_CONFIG_H -I. -I..  -I/usr/local/include/libxml2 -I/usr/local/include -DLOCALEDIR=\"/usr/local/share/locale\" -I../include -isystem /usr/local/include -I/usr/local/include -I/usr/local/include -I/usr/local/include -O2 -pipe -I/usr/local/include -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing  -Werror -std=c99 -Wall -MT libdatovka_la-cencode.lo -MD -MP -MF .deps/libdatovka_la-cencode.Tpo -c -o libdatovka_la-cencode.lo `test -f 'cencode.c' || echo './'`cencode.c
libtool: compile:  cc -DHAVE_CONFIG_H -I. -I.. -I/usr/local/include/libxml2 -I/usr/local/include -DLOCALEDIR=\"/usr/local/share/locale\" -I../include -isystem /usr/local/include -I/usr/local/include -I/usr/local/include -I/usr/local/include -O2 -pipe -I/usr/local/include -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing -Werror -std=c99 -Wall -MT libdatovka_la-cencode.lo -MD -MP -MF .deps/libdatovka_la-cencode.Tpo -c cencode.c  -fPIC -DPIC -o .libs/libdatovka_la-cencode.o
libtool: compile:  cc -DHAVE_CONFIG_H -I. -I.. -I/usr/local/include/libxml2 -I/usr/local/include -DLOCALEDIR=\"/usr/local/share/locale\" -I../include -isystem /usr/local/include -I/usr/local/include -I/usr/local/include -I/usr/local/include -O2 -pipe -I/usr/local/include -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing -Werror -std=c99 -Wall -MT libdatovka_la-cencode.lo -MD -MP -MF .deps/libdatovka_la-cencode.Tpo -c cencode.c -o libdatovka_la-cencode.o >/dev/null 2>&1
mv -f .deps/libdatovka_la-cencode.Tpo .deps/libdatovka_la-cencode.Plo
/bin/sh ../libtool  --tag=CC   --mode=compile cc -DHAVE_CONFIG_H -I. -I..  -I/usr/local/include/libxml2 -I/usr/local/include -DLOCALEDIR=\"/usr/local/share/locale\" -I../include -isystem /usr/local/include -I/usr/local/include -I/usr/local/include -I/usr/local/include -O2 -pipe -I/usr/local/include -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing  -Werror -std=c99 -Wall -MT libdatovka_la-isds.lo -MD -MP -MF .deps/libdatovka_la-isds.Tpo -c -o libdatovka_la-isds.lo `test -f 'isds.c' || echo './'`isds.c
libtool: compile:  cc -DHAVE_CONFIG_H -I. -I.. -I/usr/local/include/libxml2 -I/usr/local/include -DLOCALEDIR=\"/usr/local/share/locale\" -I../include -isystem /usr/local/include -I/usr/local/include -I/usr/local/include -I/usr/local/include -O2 -pipe -I/usr/local/include -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing -Werror -std=c99 -Wall -MT libdatovka_la-isds.lo -MD -MP -MF .deps/libdatovka_la-isds.Tpo -c isds.c  -fPIC -DPIC -o .libs/libdatovka_la-isds.o
isds.c:1645:18: error: passing an object that undergoes default argument promotion to 'va_start' has undefined behavior [-Werror,-Wvarargs]
    va_start(ap, option);
                 ^
isds.c:1633:69: note: parameter of type 'const isds_option' is declared here
isds_error isds_set_opt(struct isds_ctx *context, const isds_option option,
                                                                    ^