LaTeX error · Fatal errors

TeX capacity exceeded, sorry

The error in the log

This is how the message appears in the .log file (and in the compile output). The line starting with l. is the line number where TeX noticed the problem; the real mistake is there or just before it.

! TeX capacity exceeded, sorry [input stack size=10000].
\ref #1->(\ref {#1
                  })
l.5 See Section~\ref{sec:intro}

Why it happens

• A command redefined to call itself: \renewcommand{\ref}[1]{(\ref{#1})} or \renewcommand{\emph}[1]{\textbf{\emph{#1}}}.
• Two macros that call each other, or a loop whose stop condition is never reached.
• A fragile command in a moving argument (section title, caption) that expands into itself, often with old packages.
• A genuinely large job: huge TikZ or pgfplots figures, very long tables, or thousands of labels (reported as main memory, save size or hash size).

How to fix it

Read the line just under the error: it shows the macro that was expanding, here \ref. If you redefined that command, keep a copy of the original with \let and use the copy inside the new definition.

For memory problems with large figures, externalize them (\usetikzlibrary{external} with \tikzexternalize) or compile with LuaLaTeX, whose memory grows as needed.

Broken: reproduces the error

\documentclass{article}
\renewcommand{\ref}[1]{(\ref{#1})}
\begin{document}
\section{Intro}\label{sec:intro}
See Section~\ref{sec:intro}.
\end{document}

Fixed: compiles cleanly

\documentclass{article}
\let\oldref\ref
\renewcommand{\ref}[1]{(\oldref{#1})}
\begin{document}
\section{Intro}\label{sec:intro}
See Section~\ref{sec:intro}.
\end{document}

Related errors

• Command \x already defined – \newcommand used a name that a package or LaTeX already defines.
• Emergency stop – The run was aborted; the reason is in the line after it or in the error just above.
• Dimension too large – A length went above TeX's maximum of 16383.99999pt (about 5.75 m); usually TikZ or pgfplots data.
• All LaTeX errors and warnings – The full list, grouped by cause

Frequently Asked Questions

Can I just increase TeX memory?

Only if the document is really that large. Limits such as main_memory can be raised in texmf.cnf, but an infinite loop will exhaust any amount of memory, so first check whether a command calls itself. "input stack size" almost always means recursion.

How do I redefine a command using its old definition?

Copy it first with \let\oldcmd\cmd, then use \oldcmd in the new definition: \renewcommand{\cmd}[1]{...\oldcmd{#1}...}. For commands with optional arguments use \NewCommandCopy (LaTeX 2020 and later) instead of \let.

Why does this happen with large TikZ or pgfplots figures?

Each figure is built in TeX memory before it is written out. Many plot points can exceed main memory. Reduce samples=, externalize the figures, or compile with LuaLaTeX.