Use of #pragma pack breaks standard library functionality

[br-privacore]

In types.h you use various "#pragma pack" statements, but unfortunately you do not use push and pop, so the last #pragma pack(4) is enabled for other files included after types.h. This is obviously very dangerous if you are not aware of it.

In Hostdb.cc you include gb-include.h, which includes types.h. Further down the code you include sys/types.h and ifaddrs.h. The strucs in these files are impacted by the open #pragma pack(4) :-(

The ugly hack to "swap ints" in the getLocalIps function is a direct result of a problem caused by this open #pragma pack. It modifies the layout of the ifaddrs struct, causing you to use a misaligned address pointer.

Move the include of the two system files up above the gb-include.h file, and you can remove the swapInts function and have the ifa_addr work as expected.

The correct fix of types.h (and zlib.h) would be to use #pragma pack(push, 4) and #pragma pack(pop), but who knows what that will break now that #pragma pack(4) has been "standard" in all files.

Try this code:
printf("offsetof struct ifaddrs.ifa_next: %zu\n", offsetof(struct ifaddrs, ifa_next));
printf("offsetof struct ifaddrs.ifa_name: %zu\n", offsetof(struct ifaddrs, ifa_name));
printf("offsetof struct ifaddrs.ifa_flags: %zu\n", offsetof(struct ifaddrs, ifa_flags));
printf("offsetof struct ifaddrs.ifa_addr: %zu\n", offsetof(struct ifaddrs, ifa_addr));
printf("offsetof struct ifaddrs.ifa_netmask: %zu\n", offsetof(struct ifaddrs, ifa_netmask));

With no types.h included:
offsetof struct ifaddrs.ifa_next: 0
offsetof struct ifaddrs.ifa_name: 8
offsetof struct ifaddrs.ifa_flags: 16
offsetof struct ifaddrs.ifa_addr: 24
offsetof struct ifaddrs.ifa_netmask: 32

With types.h included (or just #pragma pack(4) specified):
offsetof struct ifaddrs.ifa_next: 0
offsetof struct ifaddrs.ifa_name: 8
offsetof struct ifaddrs.ifa_flags: 16
offsetof struct ifaddrs.ifa_addr: 20
offsetof struct ifaddrs.ifa_netmask: 28

Notice the ifa_addr offset ...

Partial fix in our fork: privacore@f360546

[isj-privacore]

Solved in our fork in commit privacore@e4323f3
but for that you also need: privacore@3f8e094
privacore@1f63050
privacore@ce5a6cf
privacore@ef3b8a3
privacore@e57fb2f
privacore@b825365
privacore@f6efc87
privacore@7f6b3e4
privacore@8072189