Re: [PATCH] bind.2, mount_setattr.2, openat2.2, perf_event_open.2, pidfd_send_signal.2, recvmmsg.2, seccomp_unotify.2, select_tut.2, sendmmsg.2, set_thread_area.2, sysctl.2, bzero.3, getaddrinfo.3, getaddrinfo_a.3, getutent.3, mbrtowc.3, mbsinit.3, rtime.3, rtnetlink.3, strptime.3, NULL.3const, size_t.3type, void.3type, aio.7, netlink.7, unix.7: Prefer bzero(3) over memset(3)

Paul Eggert <eggert@xxxxxxxxxxx> · Thu, 5 Jan 2023 12:55:51 -0800

On 2023-01-05 12:48, Adhemerval Zanella Netto via Libc-alpha wrote:

On 05/01/23 16:37, Alejandro Colomar via Libc-alpha wrote:
bzero(3) is simpler to use, and can avoid silly mistakes that are hard
to spot.  memset(3), while it is necessary in a few very-specific cases,
should be avoided when the memory is to be zeroed.

POSIX and ISO can say otherwise, but it doesn't make any sense to
recommend using memset(3) over bzero(3).

bzero is deprecated by POSIX.1-2001, removed by POSIX.1-2008, and on glibc
implementation now calls memset (previously some architecture added ifunc
redirection to optimized bzero to avoid the extra function call, it was
removed from all architectures).

Also, GCC for some time also replaces bzero with memset so there is no gain
in actually call bzero (check glibc commit 9403b71ae97e3f1a91c796ddcbb4e6f044434734).

In addition, gcc -Wall warns if you mistakenly pass 0 as memset's 3rd 
arg, which undercuts the argument that bzero avoids silly mistakes.