Problem with defernumbers and biber

[plk]

I wonder if one of the real TeX experts can look at this? Given:

\documentclass{article}
\usepackage[backend=biber,style=numeric-comp,defernumbers]{biblatex}
\begin{document}
\newrefsection[biblatex-examples.bib]
\cite{bertram,companion}
\printbibliography
\end{document}

and the sequence latex,biber,latex

the .aux file contains incorrectly:

\abx@aux@number{2}{bertram}{1}{3}
\abx@aux@number{3}{companion}{1}{4}

instead of

\abx@aux@number{2}{bertram}{1}{1}
\abx@aux@number{3}{companion}{1}{2}

Running latex once more fixes it. This is odd. It seems that in biblatex2.sty,

blx@labelnumber@\the\c@refsection

is being incremented twice for some reason and then this is written to the .aux, causing the the second latex after biber to pick up a number one higher than it should and the label is incorrect in the output. Running latex once more and it's fine thereafter. I suspect it's something fairly simple but I can't see it ...

[aboruvka]

I haven't looked at this one in earnest yet. If it's any consolation a more severe variant of this issue goes back to at least 1.7. With that release the "rerun LaTeX" message is persistent and the labelnumbers get incremented indefinitely.

[plk]

There are only a few places in the 2.0 code (4 I think) where a "+1" occurs and two of them are to increment this counter. One of them increments when it reads the .aux line mentioned above but the issue is before that, when it first writes the .aux. I can't really work out how on earth it corrects itself after the third latex run unless it's not reading the .aux file at that point.

[aboruvka]

Can you test this one again - preferably with dev 2.3? I went through the logs and I get rerun LaTeX warnings for the first two LaTeX runs after biber. As long as the first run that does not invoke this warning gives the correct aux output, I don't think this should be consider an issue.

[plk]

Good point. I tried this with 2.3 and it's as you say. There are no re-run messages when the .aux file has settled down to the correct value. I just noticed that p. 116 of the 2.3 PDF doc explicitly says that defernumbers requires 2 runs after bibtex. This clearly applies to any backend so I'll update the docs and close this. There seems to be no issue with biblatex 2.3, itis behaving as documented.