Build error on aarch64: cc1: note: unrecognized command-line option ‘-Wno-unused-command-line-argument’ may have been intended to silence earlier diagnostics

[vochong]

On RPI4b/aarch64/gcc version 11.2. and either with or without -DNO_DEFAULT_ROUTES, I encountered the following error. However, if I added the flag -O2, no such error was seen.

src/vpn.c: At top level:
cc1: note: unrecognized command-line option ‘-Wno-unused-command-line-argument’ may have been intended to silence earlier diagnostics
strip dsvpn

Full log:

$ env OPTFLAGS=-DNO_DEFAULT_ROUTES make
cc $(cat ".cflags") -DNO_DEFAULT_ROUTES -Iinclude -o dsvpn src/vpn.c src/charm.c src/os.c
In function ‘event_loop’,
    inlined from ‘doit’ at src/vpn.c:487:12,
    inlined from ‘main’ at src/vpn.c:628:9:
src/vpn.c:457:29: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
  457 |                     rbuf[i] = rbuf[len_with_header + i];
      |                     ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
src/vpn.c: In function ‘main’:
src/vpn.c:11:19: note: at offset 2 into destination object ‘len’ of size 2
   11 |     unsigned char len[2];
      |                   ^~~
In function ‘event_loop’,
    inlined from ‘doit’ at src/vpn.c:487:12,
    inlined from ‘main’ at src/vpn.c:628:9:
src/vpn.c:457:29: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
  457 |                     rbuf[i] = rbuf[len_with_header + i];
      |                     ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
src/vpn.c: In function ‘main’:
src/vpn.c:11:19: note: at offset 3 into destination object ‘len’ of size 2
   11 |     unsigned char len[2];
      |                   ^~~
In function ‘event_loop’,
    inlined from ‘doit’ at src/vpn.c:487:12,
    inlined from ‘main’ at src/vpn.c:628:9:
src/vpn.c:457:29: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
  457 |                     rbuf[i] = rbuf[len_with_header + i];
      |                     ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
src/vpn.c: In function ‘main’:
src/vpn.c:11:19: note: at offset 4 into destination object ‘len’ of size 2
   11 |     unsigned char len[2];
      |                   ^~~
In function ‘event_loop’,
    inlined from ‘doit’ at src/vpn.c:487:12,
    inlined from ‘main’ at src/vpn.c:628:9:
src/vpn.c:457:29: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
  457 |                     rbuf[i] = rbuf[len_with_header + i];
      |                     ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
src/vpn.c: In function ‘main’:
src/vpn.c:11:19: note: at offset 5 into destination object ‘len’ of size 2
   11 |     unsigned char len[2];
      |                   ^~~
src/vpn.c: At top level:
cc1: note: unrecognized command-line option ‘-Wno-unused-command-line-argument’ may have been intended to silence earlier diagnostics
strip dsvpn

gcc version 11.2.0 (GCC) Linux rpi4b 5.15.36-1-MANJARO-ARM-RPI #1 SMP PREEMPT Thu Apr 28 17:35:21 UTC 2022 aarch64 GNU/Linux