Boost logo

Boost :

Subject: Re: [boost] Legal problem with Stackoverflow contribution under the "Creative Commons Attribution Share Alike 3.0" license
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2018-02-20 19:07:26

>> Let me repeat: the only reason that my use of SO code snippets was
>> noticed is because I added a comment linking back to the original.
> Current generation software designed to find copyright and IP code infringement
> in source code do not need the author to put notices in the source code. They
> can even find instances of infringement where the author deliberately acted to
> obscure the infringement, by, for example, changing variables or hiding
> critical code in small functions or macros or etc.

I am more familiar with this than most. You can rewrite code into a
different programming language and it may still infringe. Simply
rewriting a routine will not make infringement magically disappear,
despite most programmers thinking this to be the case that if it isn't
exactly the same, it's not infringing.

But in any case all this is moot. No copyright is being infringed in any
case due to the AFC test, which for the record I applied before choosing
to reuse this snippet, as I do for all snippets I reuse from
StackOverflow. This eliminates problems with IP ownership, which is why
I do it.

I am not incompetent at my job or as a software engineer. I do not make
choices on IP in ignorance or laziness. Unlike most engineers, I
actively read case law as a hobby. In a different life I would have
entered law. I know what I am talking about, and I would have wished to
have been trusted on my opinion on this.

But okay, let's take the long road on this, as my expert opinion clearly
carries zero weight here.

> You obviously didn't act to obscure anything. But Dominique has said such
> software has flagged the code. Enough said. The rational path is to just
> rewrite the code and move on. Honest mistakes happen in code all the time.

No, he said that his legal team flagged it. And that's because it has a
source attributing comment. Had I not commented on its source, nothing
would have been flagged by his legal team. Like all the other
stackoverflow reuse, it would have slipped by without comment.

Here is the "problem" routine in full:

ULONGLONG MyTickCount64(void)
    static volatile DWORD count = 0xFFFFFFFF;
    DWORD previous_count, current_tick32, previous_count_zone,
    ULONGLONG current_tick64;

    previous_count = InterlockedCompareExchange(&count, 0, 0);
    current_tick32 = GetTickCount();

    if (previous_count == 0xFFFFFFFF)
        // count has never been written
        DWORD initial_count;
        initial_count = current_tick32 >> 28;
        previous_count = InterlockedCompareExchange(&count,
initial_count, 0xFFFFFFFF);

        current_tick64 = initial_count;
        current_tick64 <<= 28;
        current_tick64 += current_tick32 & 0x0FFFFFFF;
        return current_tick64;

    previous_count_zone = previous_count & 15;
    current_tick32_zone = current_tick32 >> 28;

    if (current_tick32_zone == previous_count_zone)
        // The top four bits of the 32-bit tick count haven't changed
since count was last written.
        current_tick64 = previous_count;
        current_tick64 <<= 28;
        current_tick64 += current_tick32 & 0x0FFFFFFF;
        return current_tick64;

    if (current_tick32_zone == previous_count_zone + 1 ||
(current_tick32_zone == 0 && previous_count_zone == 15))
        // The top four bits of the 32-bit tick count have been
incremented since count was last written.
        InterlockedCompareExchange(&count, previous_count + 1,
        current_tick64 = previous_count + 1;
        current_tick64 <<= 28;
        current_tick64 += current_tick32 & 0x0FFFFFFF;
        return current_tick64;

    // Oops, we weren't called often enough, we're stuck
    return 0xFFFFFFFF;

Let's apply, so
stage 1 is Abstraction into individual operations which is what
copyright is actually on, not the specific textual form as most
programmer think:

1. Persist a count variable across calls of the function.

2. If count is not initialised, store the top four bits of the 32 bit
count, and exit.

3. Are the top four bits of the 32 bit count same as last time we were
called? If so, exit.

4. Update the persisted count variable with the new top four bits of the
32 bit count, and adjust the value returned to account for the 32 bit
wrap so it is accurate.

5. If the top four bits overflowed since the last time we were called,
return a failure.

Now apply the Filtration stage where we remove (i) elements dictated by
efficiency, (ii) elements dictated by external factors, and (iii)
elements taken from the public domain:

1. This is standard programming, and so in the public domain. Remove.

2. The call to fetch the 32 bit count and use of atomics is dictated by
external factors. Remove. The only remaining item is the choice of top
four bits.

3. All standard programming. Remove.

4. All standard programming and external factors. Remove.

5. Returning from a function is standard programming. Remove. That
leaves those top four bits again.

The final part of Filtration stage is whether the choice of four bits is
an element dictated by efficiency. Two bits wouldn't allow detection of
overflow. Six bits is overkill and detracts from efficiency. So we can
remove the choice of four bits.

Finally we move onto the Comparison stage: compare what is remaining
after the previous two stages to see if copyright has been infringed.
Except, as I just proved, **there is nothing remaining**. So therefore
copyright cannot have been infringed by the AFC legal test. The routine
is not different from what any skilled programmer would have written if
implementing the same thing. Therefore no copyright applies. This use is
fair use under US law, de minimis under other jurisdictions.

*Every programmer* should be applying the AFC test to any code they
study if they are replicating any of its behaviour. Otherwise they may
quite easily infringe on copyright. Simply rewriting a routine does not
help. Using a different programming language does not help. Replacing
one routine with another which does the exact same thing does not help.

I stand by my claim that no copyright violation has occurred here. There
is nothing to hold copyright upon. I look forward to seeing what the SFC
lawyers say regarding this specific instance (feel free to send them a
copy of the above discussion).


ned Productions Limited Consulting

Boost list run by bdawes at, gregod at, cpdaniel at, john at