$ gcc -g -O0 -nostdlib main.c ident.S
$ valgrind ./a.out
==1147== Memcheck, a memory error detector
==1147== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==1147== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info
==1147== Command: ./a.out
==1147== 
==1147== Invalid write of size 4
==1147==    at 0x400113: ???
==1147==  Address 0x7fb0039e0 is not stack'd, malloc'd or (recently) free'd
==1147== 
Illegal instruction (core dumped) 
$ cat main.c
int
_start(int argc, char **argv)
{
        int a[10];

        a[argc + 20] = 0; // toast
}
$ cat ident.S
.section ".note.netbsd.ident", "a", @note
.long 2f-1f
.long 4f-3f
.long 1
1: .asciz "NetBSD"
2: .p2align 2
3: .long 700000001
4: .p2align 2