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P2334R1 Add support for preprocessing directives elifdef and elifndef #4992

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Oct 15, 2021
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P2334R1 Add support for preprocessing directives elifdef and elifndef #4992

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27 changes: 16 additions & 11 deletions source/preprocessor.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -80,7 +80,9 @@

\begin{bnf}\obeyspaces
\nontermdef{elif-group}\br
\terminal{\# elif } constant-expression new-line \opt{group}
\terminal{\# elif } constant-expression new-line \opt{group}\br
\terminal{\# elifdef } constant-expression new-line \opt{group}\br
\terminal{\# elifndef} constant-expression new-line \opt{group}
\end{bnf}

\begin{bnf}\obeyspaces
Expand Down Expand Up @@ -399,7 +401,9 @@
\end{floattable}

\pnum
The \tcode{\#ifdef} and \tcode{\#ifndef} directives, and
The
\tcode{\#ifdef}, \tcode{\#ifndef}, \tcode{\#elifdef}, and \tcode{\#elifndef}
directives, and
the \tcode{defined} conditional inclusion operator,
shall treat \xname{has_include} and \xname{has_cpp_attribute}
as if they were the names of defined macros.
Expand Down Expand Up @@ -491,20 +495,21 @@
\pnum
Preprocessing directives of the forms
\begin{ncsimplebnf}\obeyspaces
\terminal{\# ifdef } identifier new-line \opt{group}\br
\terminal{\# ifdef } identifier new-line \opt{group}\br
\indextext{\idxcode{\#ifdef}}%
\terminal{\# ifndef } identifier new-line \opt{group}
\terminal{\# ifndef } identifier new-line \opt{group}\br
\indextext{\idxcode{\#ifndef}}%
\terminal{\# elifdef } identifier new-line \opt{group}\br
\indextext{\idxcode{\#elifdef}}%
\terminal{\# elifndef} identifier new-line \opt{group}
\indextext{\idxcode{\#elifndef}}%
\end{ncsimplebnf}
check whether the identifier is or is not currently defined as a macro name.
Their conditions are equivalent to
\tcode{\#if}
\tcode{defined}
\grammarterm{identifier}
and
\tcode{\#if}
\tcode{!defined}
\grammarterm{identifier}
\tcode{\#if} \tcode{defined} \grammarterm{identifier},
\tcode{\#if} \tcode{!defined} \grammarterm{identifier},
\tcode{\#elif} \tcode{defined} \grammarterm{identifier}, and
\tcode{\#elif} \tcode{!defined} \grammarterm{identifier},
respectively.

\pnum
Expand Down