# hyperref and theorems counted by subsection- “pdftex warning (ext4) destination with same identifier”

I have got some problems with hyperref and theorems labeled by subsections: To get the theorems labeled correctly I manually reset the thm counter also at the beginning of new sections. But then I get problems with hyperref. Take for example

\documentclass[a4paper, 11pt] {article}
\usepackage{hyperref}

\newtheorem{thm}{Theorem}[subsection]
\newtheorem{prop}[thm]{Proposition}

\makeatletter
\makeatother

\begin{document}
\section{One}
\subsection{Oneone} \label{ss11}
\begin{prop} \label{p1}
\end{prop}

\subsection{twoone}
\begin{prop} \label{p2}
\end{prop}

Ref \ref{p1} and \ref{p2}.
\end{document}


This gives the warning:

pdfTeX warning (ext4): destination with the same identifier (name{thm.1.1}) has been already used, duplicate ignored


I have already browsed the web and found some similar issue here but the answer does not apply in my case due to the \@addtoreset line.

Note that the problem does not occur if I either remove the \@addtoreset{thm}{section} or if there is just one subsection.

Thank you very much!

You need to make the internal counter of hyperref for thm \theHthm unique. E.g.

\documentclass[a4paper, 11pt] {article}
\usepackage{hyperref}

\newtheorem{thm}{Theorem}[subsection]
\newtheorem{prop}[thm]{Proposition}

\makeatletter
\renewcommand\theHthm{\thesection.\thethm}
\makeatother

\begin{document}
\section{One}
\subsection{Oneone} \label{ss11}
\begin{prop} \label{p1}
\end{prop}

\subsection{twoone}
\begin{prop} \label{p2}
\end{prop}

Ref \ref{p1} and \ref{p2}.
\end{document}