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The following document will not compile (using xelatex, biber) if the package gb4e is activated. If you comment out the gb4e package it works fine:

\documentclass{article}
\usepackage{fontspec}
\setromanfont{Times New Roman}
% \usepackage{gb4e} % <-- FAILS WITH THIS PACKAGE ACTIVATED

\usepackage[nopar]{lipsum} % for dummy text
\usepackage[american]{babel}
\usepackage[authordate,isbn=false,backend=biber]{biblatex-chicago}  

\begin{filecontents}{\jobname.bib}
@book{Saussure1995,
    Author = {Ferdinand de Saussure},
    Origyear = {1916},
    Publisher = {Payot},
    Title = {Cours de Linguistique Générale},
    Year = {1995}}
\end{filecontents}
\addbibresource{\jobname.bib}

\begin{document}
\section*{Les Présentations}
\lipsum[1] \autocite{Saussure1995}   
\printbibliography
\end{document}

Any help would be greatly appreciated.

Michael Dunn
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  • Welcome to TeX.sx! It seems that loading gb4e after biblatex fixes the problem, at least with the MWE. – egreg Mar 07 '13 at 13:50
  • Thanks, the oldest trick in the book! Frustratingly however although it works in my MWE, it doesn't help my real document. I'll look at it some more. – Michael Dunn Mar 07 '13 at 14:08
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    That's what I feared. You can try putting \noautomath just after loading gb4e, which disables the special usage of _ that, I believe, is responsible for the incompatibility. – egreg Mar 07 '13 at 14:20
  • Amazing, that worked! I can reproduce the error in the MWE if I use underscores in labels of the references, e.g. Saussure_1916. – Michael Dunn Mar 07 '13 at 14:23

1 Answers1

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In the gb4e.sty package one finds this comment:

    %  This file allows _ and ^ to be used in ordinary text, hence must be
    %  loaded AFTER any file that uses them in their TeX meaning. Hence
    %  cgloss(n).sty is loaded early in this file.  This feature is known to
    %  cause some problems with other packages, but is maintained for backward 
    %  compatibility. If you have problems, you can try disabling it by
    %  placing the command \noautomath immediately after loading the gb4e package.
    %  [Added 2009/12/28]

The definition it gives of the active underscore is

% \automath     Make _ and ^ work outside math mode
% \noautomath   Restore normal sub/superscript behavior

{ % Temporarily change catcodes
  \catcode`\_=\active
  \catcode`\^=\active

  \global\def\automath{%
    \catcode`\_=\active
    \catcode`\^=\active
    \def_##1{\gb@ifnextchar^{\automath@two_{##1}}{\ensuremath{\sb{##1}}}}%
    \def^##1{\gb@ifnextchar_{\automath@two^{##1}}{\ensuremath{\sp{##1}}}}}
}
\def\automath@two#1#2#3#4{\ensuremath{#1{#2}\relax #3{#4}}}
% Restore default catcodes for ^, _
\def\noautomath{\catcode`\_=8 \catcode`\^=7 }

which is, in my opinion, bad. Indeed the package authors thought it better to provide a way for disabling it. In any case, when \automath is enabled (which it is by default), the underscore cannot be used in labels.

So my best advice is doing

\usepackage{gb4e}
\noautomath
egreg
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