dest

The article also suggests using strncat for this: dest[0] = '\0'; strncat(dest, src, size);.

I found it more comprehensive than wget's recursive mode, but I haven't compared it to rsync --link-dest.

I've even seen things like strncpy(dest, src, strlen(src)); which is certainly no safer than strcpy().

How are you doing dest unreachable/ttl exceeded without this, for example?

I verified this using 'frame' in gdb using the source (RSP) and dest addresses.

For example, doing a strcpy(dest, dest + 1) will work in most cases, but if done on 64-bit Linux with a CPU that has sse4 optimizations, you will get random corruption on certain string lengths.

Don't worry about the instruction, worry about dest, src.

Much better to break it up into many threads, something like: rsync -av /source/giant/tree/subdir1 /dest/giant/tree/subdir1 rsync -av /source/giant/tree/subdir2 /dest/giant/tree/subdir2 rsync -av /source/giant/tree/subdir3 /dest/giant/tree/subdir3 That alone probably would have dramatically sped things up, BUT you do still have your speed of light issues.

This: strncpy(dest, source, size); can be replaced by this: dest[0] = '\0'; strncat(dest, source, size); which will leave the destination properly null-terminated.

Thus there was some communication between my IP & dest IP at some time, and is in a log if routers keep logs (or any other device that is physically connected to the same physical path that my packets took) Sounds like TOR hidden services don't create breadcrumbs like this then.

Backups: check out rsync's "--link-dest" option.

> You won't find data-dependent branches or look-ups in straightforward implementations of Curve25519 As it was pointed out already starting since Pentium 4, for example, the same assembly instruction "add dest, src" might take a different time depending on the value of dest and src.

I would make a less-strict statement that "Undefined behavior should be reserved for cases where there might be some advantage for an implementation to do it a different way." For memcpy it's never safe for it to access the byte at "src+len" (it could be past the end of mapped memory) nor is it safe to write to "dest+len" So if len==0 it should follow that it won't access either src[0] or dest[0].

Some examples: ((mut () env (assoc env:foo 1))); equivalent to (define foo 1) ((mut () env (assoc env:my-define (mut (dest src) env (assoc env dest src))))); this is actually how `define` is defined ((mut () env (map))) ((+ 1 1)); throws exception "undefined symbol +" because previous line emptied the environment The "everything takes env" bit is inspired by J.