compiler warning

[perkelix]

dhcpcd 10.3.1 building with GCC 15:

cc -g -O2 -Werror=implicit-function-declaration -ffile-prefix-map=/home/perkelix/Projects/Salsa/dhcpcd=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -g -Wall -Wextra -Wundef -Wmissing-prototypes -Wmissing-declarations -Wmissing-format-attribute -Wnested-externs -Winline -Wcast-align -Wcast-qual -Wpointer-arith -Wreturn-type -Wswitch -Wshadow -Wcast-qual -Wwrite-strings -Wformat=2 -Wpointer-sign -Wmissing-noreturn -Wredundant-decls -Wconversion -Wstrict-overflow -std=c99 -Wdate-time -D_FORTIFY_SOURCE=2 -I/include -DHAVE_CONFIG_H -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -DINET -DARP -DARPING -DIPV4LL -DINET6 -DDHCP6 -DAUTH -DPRIVSEP -DPLUGIN_DEV -I.. -I../src -I./crypt -I../vendor -c dev.c -o dev.o
if-linux.c: In function ‘if_address’:
if-linux.c:1279:17: warning: writing 16 bytes into a region of size 12 [-Wstringop-overflow=]
1279 | memcpy(RTA_DATA(rta), data, alen);
| ^
if-linux.c:1584:25: note: at offset [4, 16] into destination object ‘hdr’ of size 16
1584 | struct nlmsghdr hdr;
| ^~~
cc -g -O2 -Werror=implicit-function-declaration -ffile-prefix-map=/home/perkelix/Projects/Salsa/dhcpcd=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -g -Wall -Wextra -Wundef -Wmissing-prototypes -Wmissing-declarations -Wmissing-format-attribute -Wnested-externs -Winline -Wcast-align -Wcast-qual -Wpointer-arith -Wreturn-type -Wswitch -Wshadow -Wcast-qual -Wwrite-strings -Wformat=2 -Wpointer-sign -Wmissing-noreturn -Wredundant-decls -Wconversion -Wstrict-overflow -std=c99 -Wdate-time -D_FORTIFY_SOURCE=2 -I/include -DHAVE_CONFIG_H -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -DINET -DARP -DARPING -DIPV4LL -DINET6 -DDHCP6 -DAUTH -DPRIVSEP -DPLUGIN_DEV -I.. -I../src -I./crypt -I../vendor -c privsep.c -o privsep.o
if-linux.c: In function ‘if_address6’:
if-linux.c:1279:17: warning: writing 16 bytes into a region of size 12 [-Wstringop-overflow=]
1279 | memcpy(RTA_DATA(rta), data, alen);
| ^
if-linux.c:1584:25: note: at offset [4, 16] into destination object ‘hdr’ of size 16
1584 | struct nlmsghdr hdr;
| ^~~
cc -g -O2 -Werror=implicit-function-declaration -ffile-prefix-map=/home/perkelix/Projects/Salsa/dhcpcd=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -g -Wall -Wextra -Wundef -Wmissing-prototypes -Wmissing-declarations -Wmissing-format-attribute -Wnested-externs -Winline -Wcast-align -Wcast-qual -Wpointer-arith -Wreturn-type -Wswitch -Wshadow -Wcast-qual -Wwrite-strings -Wformat=2 -Wpointer-sign -Wmissing-noreturn -Wredundant-decls -Wconversion -Wstrict-overflow -std=c99 -Wdate-time -D_FORTIFY_SOURCE=2 -I/include -DHAVE_CONFIG_H -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -DINET -DARP -DARPING -DIPV4LL -DINET6 -DDHCP6 -DAUTH -DPRIVSEP -DPLUGIN_DEV -I.. -I../src -I./crypt -I../vendor -c privsep-root.c -o privsep-root.o

[rsmarples]

This looks like a false positive to me because we use a structure which adds space to the end. Maybe we can use a union instead to tell the compiler better.