This bug was suddently triggered by Appveyor compilation and seems to make sense.
[-] CC argtable3.c
inlined from 'arg_cat_option' at argtable3.c:4208:13,
inlined from 'arg_print_syntax' at argtable3.c:4392:9:
argtable3.c:4149:11: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
4149 | *dest = 0;
| ~~~~~~^~~
argtable3.c: In function 'arg_print_syntax':
argtable3.c:4381:14: note: at offset 200 to object 'syntax' with size 200 declared here
4381 | char syntax[200] = "";
| ^~~~~~
8a9c7d2efc