In the BlueZ build, we apparently use stricter Warn to Error checking than what is currently set up for ELL. I got my son a new Raspberry PI, and the first thing he tried to build was ELL and BlueZ... On THAT PATFORM ONLY, Raspbian (Raspbian 10 (buster)) with kernel 4.19, we get failures building ell/dbus.c. Everything builds correctly in the ELL tree, using standard bootstrap-configure, however when using -Werror=cast-align, I get the following (see below) build issues in dbus.c, genl.c, dhcp-transport.c, plus a few unit tests... In BlueZ these errors show up with the *default* build procedure: So my question for Marcel is: Do we need the alignment check in BlueZ? And for Denis and Marcel, Do we care if there are alignment warnings in ELL? Here is a dump of the make output after: $ export CFLAGS=-Werror=cast-align $ ./bootstrap-configure pi@raspberrypi:~/ell $ make -k make --no-print-directory all-am CC ell/genl.lo ell/genl.c: In function ‘l_genl_attr_next’: ell/genl.c:1677:5: error: cast increases required alignment of target type [-Werror=cast-align] (struct nlattr*)(((char*)(nla)) + \ ^ ell/genl.c:1738:20: note: in expansion of macro ‘NLA_NEXT’ attr->next_data = NLA_NEXT(nla, attr->next_len); ^~~~~~~~ cc1: all warnings being treated as errors make[1]: *** [Makefile:1864: ell/genl.lo] Error 1 CC ell/dbus.lo In file included from ell/dbus.c:38: ell/dbus.c: In function ‘classic_free’: ell/util.h:40:3: error: cast increases required alignment of target type [-Werror=cast-align] (type *)((char *) __mptr - offsetof(type, member)); \ ^ ell/dbus.c:582:3: note: in expansion of macro ‘l_container_of’ l_container_of(dbus, struct l_dbus_classic, super); ^~~~~~~~~~~~~~ ell/dbus.c: In function ‘classic_recv_message’: ell/util.h:40:3: error: cast increases required alignment of target type [-Werror=cast-align] (type *)((char *) __mptr - offsetof(type, member)); \ ^ ell/dbus.c:661:3: note: in expansion of macro ‘l_container_of’ l_container_of(dbus, struct l_dbus_classic, super); ^~~~~~~~~~~~~~ ell/dbus.c: In function ‘classic_add_match’: ell/util.h:40:3: error: cast increases required alignment of target type [-Werror=cast-align] (type *)((char *) __mptr - offsetof(type, member)); \ ^ ell/dbus.c:812:3: note: in expansion of macro ‘l_container_of’ l_container_of(dbus, struct l_dbus_classic, super); ^~~~~~~~~~~~~~ ell/dbus.c: In function ‘classic_remove_match’: ell/util.h:40:3: error: cast increases required alignment of target type [-Werror=cast-align] (type *)((char *) __mptr - offsetof(type, member)); \ ^ ell/dbus.c:836:3: note: in expansion of macro ‘l_container_of’ l_container_of(dbus, struct l_dbus_classic, super); ^~~~~~~~~~~~~~ cc1: all warnings being treated as errors make[1]: *** [Makefile:1864: ell/dbus.lo] Error 1 CC ell/dhcp-transport.lo In file included from ell/dhcp-transport.c:44: ell/dhcp-transport.c: In function ‘_dhcp_default_transport_broadcast’: ell/util.h:40:3: error: cast increases required alignment of target type [-Werror=cast-align] (type *)((char *) __mptr - offsetof(type, member)); \ ^ ell/dhcp-transport.c:203:3: note: in expansion of macro ‘l_container_of’ l_container_of(s, struct dhcp_default_transport, super); ^~~~~~~~~~~~~~ ell/dhcp-transport.c: In function ‘_dhcp_default_transport_send’: ell/util.h:40:3: error: cast increases required alignment of target type [-Werror=cast-align] (type *)((char *) __mptr - offsetof(type, member)); \ ^ ell/dhcp-transport.c:246:3: note: in expansion of macro ‘l_container_of’ l_container_of(s, struct dhcp_default_transport, super); ^~~~~~~~~~~~~~ ell/dhcp-transport.c: In function ‘_dhcp_default_transport_bind’: ell/util.h:40:3: error: cast increases required alignment of target type [-Werror=cast-align] (type *)((char *) __mptr - offsetof(type, member)); \ ^ ell/dhcp-transport.c:316:3: note: in expansion of macro ‘l_container_of’ l_container_of(s, struct dhcp_default_transport, super); ^~~~~~~~~~~~~~ ell/dhcp-transport.c: In function ‘_dhcp_default_transport_open’: ell/util.h:40:3: error: cast increases required alignment of target type [-Werror=cast-align] (type *)((char *) __mptr - offsetof(type, member)); \ ^ ell/dhcp-transport.c:454:3: note: in expansion of macro ‘l_container_of’ l_container_of(s, struct dhcp_default_transport, super); ^~~~~~~~~~~~~~ ell/dhcp-transport.c: In function ‘_dhcp_default_transport_close’: ell/util.h:40:3: error: cast increases required alignment of target type [-Werror=cast-align] (type *)((char *) __mptr - offsetof(type, member)); \ ^ ell/dhcp-transport.c:476:3: note: in expansion of macro ‘l_container_of’ l_container_of(s, struct dhcp_default_transport, super); ^~~~~~~~~~~~~~ cc1: all warnings being treated as errors make[1]: *** [Makefile:1864: ell/dhcp-transport.lo] Error 1 CC unit/test-genl-msg.o unit/test-genl-msg.c: In function ‘parse_set_station’: unit/test-genl-msg.c:63:10: error: cast increases required alignment of target type [-Werror=cast-align] nlmsg = (struct nlmsghdr *) set_station_request; ^ unit/test-genl-msg.c: In function ‘parse_set_rekey_offload’: unit/test-genl-msg.c:159:10: error: cast increases required alignment of target type [-Werror=cast-align] nlmsg = (struct nlmsghdr *) set_rekey_offload_request; ^ unit/test-genl-msg.c: In function ‘parse_libnl_nested’: unit/test-genl-msg.c:287:10: error: cast increases required alignment of target type [-Werror=cast-align] nlmsg = (struct nlmsghdr *) libnl_nested; ^ cc1: all warnings being treated as errors make[1]: *** [Makefile:1848: unit/test-genl-msg.o] Error 1 CC unit/test-dbus-watch.o In file included from ./ell/ell.h:23, from unit/test-dbus-watch.c:30: unit/test-dbus-watch.c: In function ‘test_add_match’: ./ell/util.h:40:3: error: cast increases required alignment of target type [-Werror=cast-align] (type *)((char *) __mptr - offsetof(type, member)); \ ^ unit/test-dbus-watch.c:111:3: note: in expansion of macro ‘l_container_of’ l_container_of(dbus, struct filter_test_state, dbus); ^~~~~~~~~~~~~~ unit/test-dbus-watch.c: In function ‘test_remove_match’: ./ell/util.h:40:3: error: cast increases required alignment of target type [-Werror=cast-align] (type *)((char *) __mptr - offsetof(type, member)); \ ^ unit/test-dbus-watch.c:127:3: note: in expansion of macro ‘l_container_of’ l_container_of(dbus, struct filter_test_state, dbus); ^~~~~~~~~~~~~~ cc1: all warnings being treated as errors make[1]: *** [Makefile:1848: unit/test-dbus-watch.o] Error 1 make[1]: Target 'all-am' not remade because of errors. make: *** [Makefile:1199: all] Error 2 pi@raspberrypi:~/ell $