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P1874R1 Dynamic Initialization Order of Non-Local Variables in Modules #3438

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Nov 20, 2019
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P1874R1 Dynamic Initialization Order of Non-Local Variables in Modules #3438

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37 changes: 24 additions & 13 deletions source/basic.tex
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Expand Up @@ -6343,31 +6343,42 @@
variable template specialization has ordered initialization.
\end{note}

\pnum
A declaration \tcode{D} is
\defn{appearance-ordered} before a declaration \tcode{E} if
\begin{itemize}
\item \tcode{D} appears in the same translation unit as \tcode{E}, or
\item the translation unit containing \tcode{E}
has an interface dependency on the translation unit containing \tcode{D},
\end{itemize}
in either case prior to \tcode{E}.
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It's not clear what we're talking about in this last phrase, especially when applied to the 2nd bullet. Can this be clarified?

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This is intentionally handwaving around our not having precise wording for this constraint; the same handwaving occurs in [module.reach]p1. Filed #3502 to track this.


\pnum
Dynamic initialization of non-local variables \tcode{V} and \tcode{W}
with static storage duration are ordered as follows:
\begin{itemize}
\item
If \tcode{V} and \tcode{W} have
ordered initialization and \tcode{V} is defined before \tcode{W} within
a single translation unit, the initialization of \tcode{V} is sequenced
before the initialization of \tcode{W}.

\item
If \tcode{V} has partially-ordered initialization, \tcode{W} does not have
unordered initialization, and \tcode{V} is defined before \tcode{W} in
every translation unit in which \tcode{W} is defined, then
If \tcode{V} and \tcode{W} have ordered initialization and
the definition of \tcode{V}
is appearance-ordered before the definition of \tcode{W}, or
if \tcode{V} has partially-ordered initialization,
\tcode{W} does not have unordered initialization, and
for every definition \tcode{E} of \tcode{W}
there exists a definition \tcode{D} of \tcode{V}
such that \tcode{D} is appearance-ordered before \tcode{E}, then
\begin{itemize}
\item
if the program starts a thread\iref{intro.multithread}
other than the main thread\iref{basic.start.main},
if the program does not start a thread\iref{intro.multithread}
other than the main thread\iref{basic.start.main}
or \tcode{V} and \tcode{W} have ordered initialization and
they are defined in the same translation unit,
the initialization of \tcode{V}
strongly happens before
is sequenced before
the initialization of \tcode{W};
\item
otherwise,
the initialization of \tcode{V}
is sequenced before
strongly happens before
the initialization of \tcode{W}.
\end{itemize}

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