What is the canonical way to redefine the \emph command

Question

Question says it all. What is the best way to redefine the \emph command to be bold font and upright?

Answer 1

Since \emph uses \em, I would redefine \em.

Here's such a redefinition which preserves the ability to toggle between bold and normal, if nested:

\makeatletter
\DeclareRobustCommand{\em}{%
  \@nomath\em \if b\expandafter\@car\f@series\@nil
  \normalfont \else \bfseries \fi}
\makeatother

Test of nesting behavior of \emph:

Question: \emph{What is the way to redefine the \emph{\textbackslash emph} command?}

Answer 2

According to p. 194 of the LaTeX2e sources, \emph is defined as

\DeclareTextFontCommand{\emph}{\em}

So I suggest to redefine it as follows:

\DeclareTextFontCommand{\emph}{\bfseries}