Multiple authors with different primary affiliation, but same additional affiliation

Question

I am writing a paper with 2 authors that have different primary affiliations. However, they both have a common additional affiliation. Currently, this is what I do:

%%%% Proceedings format for most of ACM conferences (with the exceptions listed below) and all ICPS volumes.
\documentclass[sigconf]{acmart}

\usepackage{booktabs} % For formal tables

\setcopyright{rightsretained}

% DOI
\acmDOI{10.475/123_4}

% ISBN
\acmISBN{123-4567-24-567/08/06}

%Conference
\acmConference[THIS '17]{Some ACM Conference}{July 2017}{Anywhere, USA} 
\acmYear{2017}
\copyrightyear{2017}

\acmPrice{15.00}

\begin{document}
\title{My Title}

\author{Author One}
\additionalaffiliation{%
  \institution{Secondary Organization}
  \city{Commonville}
  \state{State}
}
\affiliation{%
  \institution{My Company}
  \streetaddress{1234 Here Ave}
  \city{Location}
  \state{State}
  \postcode{12345}
}
\email{[email protected]}

\author{Author Two}
\additionalaffiliation{%
  \institution{Secondary Organization}
  \city{Commonville}
  \state{State}
}
\affiliation{%
  \institution{Other Company}
  \streetaddress{5678 There St}
  \city{Place} 
  \state{State} 
  \postcode{67890}
}
\email{[email protected]}

%\author{Author Two\footnotemark[1]} % Next attempt: use this line instead of \author{Author Two} and \additionalaffiliation

\begin{abstract}
Here is my abstract
\end{abstract}

\keywords{this, that, another}

\maketitle

\end{document}

Unfortunately, this creates two separate footnotes that say the exact same thing: "Also with Secondary Organization." Is there any way to just use one symbol next to both names so that they reference the same footnote?

I've also tried:

\author{Author Two\footnotemark[1]}

for the second author's name instead of using \additionalaffiliation again. This does produce the desired effect, but with a side effect too. Elsewhere in the document, when the authors are referenced, it outputs:

Author One, Author Two[1].

Answer 1

Here's a solution. I've made a new command \addauthornote which takes a single argument, a number corresponding to the n-th additional affiliation. This will add the footnote mark corresponding to that additional affiliation and add it to the current author.

Here's a complete example using 4 authors with 2 additional affiliations.

%%%% Proceedings format for most of ACM conferences (with the exceptions listed below) and all ICPS volumes.
\documentclass[sigconf]{acmart}
\makeatletter

% Use this command to add an existing supplemental affiliation to an author
% \addauthornote{1} adds n-th additional affiliation mark.   
\newcommand\addauthornote[1]{%
  \if@ACM@anonymous\else
    \g@addto@macro\addresses{\@addauthornotemark{#1}}%
  \fi}

\newcommand\@addauthornotemark[1]{\let\@tmpcnta\c@footnote
   \setcounter{footnote}{#1}\addtocounter{footnote}{-1}
    \g@addto@macro\@currentauthors{\footnotemark\relax\let\c@footnote\@tmpcnta}}

\makeatother
\usepackage{booktabs} % For formal tables

\setcopyright{rightsretained}

% DOI
\acmDOI{10.475/123_4}

% ISBN
\acmISBN{123-4567-24-567/08/06}

%Conference
\acmConference[THIS '17]{Some ACM Conference}{July 2017}{Anywhere, USA} 
\acmYear{2017}
\copyrightyear{2017}

\acmPrice{15.00}

\begin{document}
\title{My Title}

\author{Author One}
\additionalaffiliation{%
  \institution{Author 1 Secondary Organization}
  \city{Commonville}
  \state{State}
}
\affiliation{%
  \institution{My Company}
  \streetaddress{1234 Here Ave}
  \city{Location}
  \state{State}
  \postcode{12345}
}
\email{[email protected]}

\author{Author Two}
\additionalaffiliation{%
  \institution{Author 2 Secondary Organization}
  \city{Commonville}
  \state{State}
}
\affiliation{%
  \institution{My Company}
  \streetaddress{1234 Here Ave}
  \city{Location}
  \state{State}
  \postcode{12345}
}
\email{[email protected]}

\author{Author Three}
\addauthornote{2}

\affiliation{%
  \institution{Other Company}
  \streetaddress{5678 There St}
  \city{Place} 
  \state{State} 
  \postcode{67890}
}


\email{[email protected]}

\author{Author Four}
\addauthornote{1}

\affiliation{%
  \institution{Other Company}
  \streetaddress{5678 There St}
  \city{Place} 
  \state{State} 
  \postcode{67890}
}


\email{[email protected]}


\begin{abstract}
Here is my abstract
\end{abstract}

\keywords{this, that, another}

\maketitle

\end{document}