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After compiling my LaTeX document, the log file contains the message:

LaTeX Warning: There were undefined references.

How can I tell which lines and/or labels prompted this warning?

PS This question has already been asked in this comment by some other user, and the reply was that the person asking the question should ask it in a separate post, but I haven't been able to find any post that addresses this question.

Evan Aad
  • 11,066

1 Answers1

2

The message There were undefined references is one of the last things printed on screen to catch your attention to the issue. However, scrolling up to the console output or the log file will show the line number where the undefined reference was found. The file

\documentclass{article}
\begin{document}
\section{foo}\label{foo}
This is section \ref{fo}
\end{document}

returns

LaTeX Warning: Reference `fo' on page 1 undefined on input line 4.

[1{/var/lib/texmf/fonts/map/pdftex/updmap/pdftex.map}] (./mwe.aux)


LaTeX Warning: There were undefined references.

Of course, if after the undefined reference there are many pages, possibly with figures, you might have to scroll back a lot.

If you \input external files then you must keep in mind that the quoted line number always refers to the current file. Assume that we have a file foo.tex

\section{foo}\label{foo}
This is section \ref{fo}

and the main file main.tex reads

\documentclass{article}
\begin{document}
Text text.
\input{foo}
\end{document}

then the log will contain

This is pdfTeX, Version 3.14159265-2.6-1.40.18 (TeX Live 2017/TeX Live for SUSE Linux) (preloaded format=pdflatex 2019.9.25)  9 APR 2021 14:59
entering extended mode
 restricted \write18 enabled.
 %&-line parsing enabled.
**main.tex
(./main.tex
LaTeX2e <2017-04-15>

% [ ... other stuff ... ]


(./foo.tex


LaTeX Warning: Reference `fo' on page 1 undefined on input line 2.


) [1


{/var/lib/texmf/fonts/map/pdftex/updmap/pdftex.map}] (./mwe.aux)


LaTeX Warning: There were undefined references.


)
% [ ... other stuff ...]

Here the line number refers to the external file: watch out for the string (./foo.tex which means that this is the currently open file. The corresponding closing parenthesis ) is shown just after the warning; the final closing parenthesis refers to the main file (the corresponding opening one is on the 6th line).

campa
  • 31,130