\overline outside of math mode

\end{document}


Your question was essentially answered by egreg but there wasn't much explanation and this is a little too long to put as a comment.

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\documentclass{article}
\newsavebox\TBox
\def\textoverline#1{\savebox\TBox{#1}%
\makebox[0pt][l]{#1}\rule[1.1\ht\TBox]{\wd\TBox}{0.4pt}}
\begin{document}

\textoverline{foo}
\textoverline{\textit{foo\"A}}
\tiny\textoverline{bar}

\end{document}

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