Hi Dwight, > Le 17 déc. 2020 à 00:09, Dwight Guth <[email protected]> a > écrit : > > I have reproduced this error with Bison 3.7.4, but it is also present > in versions as old as 3.0.4, the oldest version I have tried.
Wow... > Note that the terminal output mentions that C is a useless > nonterminal, but if C is removed from the grammar, the error > disappears. While I am aware that the problem could be solved by > simply removing the useless nonterminal from the grammar (and have > been able to reproduce this behavior on my real-world example), the > real-world grammar is autogenerated and it would be nice if this just > worked and the useless nonterminal was ignored. Regardless, I figured > an assertion error is probably not an appropriate failure mode, so I > wanted to report the error to you. Yes, this is definitely not expected, thanks a lot for the (complete) report! > We have plans to modify our grammar generator on our end to fix the > issue in the way I described above, so this is not terribly high > priority for us, since by the time bison releases trickle out into > Linux distros, we will have already worked around the issue. But I > have seen this same error message in other contexts in the past, so > it's possible we may run into it again in a situation where it will be > harder for us to simply work around it, so a fix would still be > helpful to us long-term. I will not work on this immediately (I expect this one to be tricky, and I have ongoing business in Bison I'd like to finish first), but this is definitely in the TODO list. > I should have already completed a copyright assignment form that is > applicable for changes to Bison, and am happy to follow any steps you > have in mind in order to incorporate this minimized test into your > test suite. Just let me know what you need. I believe your test case is small enough so that we can call it "trivial" (although, I agree, finding it was not), and therefore I can use it as a contributions of yours that does not require paperwork. If, however, you'd like to contribute to Bison (for instance there's a bug report about IELR that has just arrived :-), you'll have to sign these papers. Cheers!
