Re: [PATCH 2/3] t/helper/test-delta: segfault on OOB access

> > If we want to detect this kind of thing in tests, we should probably be
> > relying on tools like ASan, which would cover all mmaps.
> >
> > It would be nice if there was a low-cost way to detect this in
> > production use, but it looks like this replaces mmap with
> > read_in_full(), which I think is a non-starter for most uses.
> 
> I think even with ASAN, you'd still need read_in_full() or an mmap()
> wrapper that fiddles with the ASAN shadow, because mmap() always maps
> whole pages:
> 
> $ cat mmap-read-asan-blah.c
> #include <sys/mman.h>
> #include <stdlib.h>
> int main(void) {
>   volatile char *p = mmap(NULL, 1, PROT_READ|PROT_WRITE,
> MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
>   p[200] = 1;
> }
> $ gcc -o mmap-read-asan-blah mmap-read-asan-blah.c -fsanitize=address
> $ ./mmap-read-asan-blah
> $