Re: Bison Skeleton: irksome GPL license.

[Hans Åberg]

> On 18 Apr 2018, at 15:56, Kaz Kylheku <address@hidden> wrote:
> 
> What I'm saying is that Flex 2.5.35 in an Ubuntu installation I'm
> using has this behavior:
> 
>  /* comment */
>  %{
>  #include "header.h"
>  %}
>  /* ... */
> 
> The header comment is propagated to the lex.yy.c file. It's not at the top
> of the file; it follows some preamble material. Then a #line 1 directive
> appears, followed by that comment.

Yes, I see that. Perhaps it is bug in Bison: there is no #line 1.

>>> That little GNU license blurb is still a problem there. A pre-built y.tab.c
>>> file could end up being packaged as a distributed file: say, for the
>>> convenience of users who don't have a Yacc installed.
>> The license applies to stuff in the skeleton M4 file that is copied
>> over, so it should be there.
> 
> Unfortunately, it doesn't clarify what it applies to; it appears to
> apply to the entire file.
> 
> It should delineate exactly which lines it applies to. Otherwise it
> is not appropriate. For instance, "The following copyright notice
> applies only to that portion of this which occurs between the symbols
> START_BISON_SKELETON and END_BISON_SKELETON".
> 
> If it is necessary to preserve that notice in a derived work such
> as y.tab.c, it follows that it must be preserved in the derived work
> y.tab.o also.

Most copyright notices don't specify exactly what is copyrighted.

>>> What I've done is added a sed filter to my build rule which basically
>>> takes that notice out of the y.tab.c right after the file is
>>> generated.
>> That wouldn't be legal: your copyright does not override the one for
>> the skeleton file contents.
> 
> It's perfectly legal; I'm allowed to do anything with that code,
> including compiling it into a proprietary executable program whose
> image contains no copyright strings.
> 
> I'm not taking away the copyright itself; just the mistaken notice.
> 
> Most importantly, I'm also not redistributing any portion of Bison.
> I'm redistributing a program, which has a Makefile, which removes
> some cruft from y.tab.c after making it with the user's installation
> of Bison.
> 
> If someone mistakenly picks up that y.tab.c into some tarball
> and redistributes it (not my action, theirs) my work is protected
> from being tainted by a misapplied license.
> The onus is on that redistributor to ensure that everything has
> the appropriate notice. I don't intend y.tab.c to be redistributed;
> for all I care, it can be regenerated each time parser.y is
> newer than parser.o, and deleted immediately after parser.o is
> produced; it's just worse that way for debugging purposes.

It is common to distribute the parser .c file as it is written to be platform 
independent, and there may be a problem with the Yacc/Bison installation. In 
such case, it would appropriate to have the notice for the M4 contents as well.