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<H1> C.5 Pragma Discard_Names</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> [A <FONT FACE="Arial, Helvetica">pragma</FONT>
Discard_Names may be used to request a reduction in storage used for
the names of certain entities.] </DIV>
<H4 ALIGN=CENTER>Syntax</H4>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="SyntaxIndented" Style="margin-bottom: 0.2em">The form of
a <FONT FACE="Arial, Helvetica">pragma</FONT> Discard_Names is as follows:
</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DIV Class="SyntaxIndented"> <B>pragma</B> <A NAME="I6688"></A>Discard_Names[([On
=> ] <A NAME="I6689"></A><FONT FACE="Arial, Helvetica">local_name</FONT>)];</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<DIV Class="SyntaxIndented">A <FONT FACE="Arial, Helvetica">pragma</FONT>
Discard_Names is allowed only immediately within a <FONT FACE="Arial, Helvetica">declarative_part</FONT>,
immediately within a <FONT FACE="Arial, Helvetica">package_specification</FONT>,
or as a configuration pragma. </DIV>
<H4 ALIGN=CENTER>Legality Rules</H4>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<DIV Class="Normal"> The <FONT FACE="Arial, Helvetica">local_name</FONT>
(if present) shall denote a non-derived enumeration [first] subtype,
a tagged [first] subtype, or an exception. The pragma applies to the
type or exception. Without a <FONT FACE="Arial, Helvetica">local_name</FONT>,
the pragma applies to all such entities declared after the pragma, within
the same declarative region. Alternatively, the pragma can be used as
a configuration pragma. If the pragma applies to a type, then it applies
also to all descendants of the type. </DIV>
<H4 ALIGN=CENTER>Static Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<DIV Class="Normal"> <A NAME="I6690"></A><A NAME="I6691"></A>If a <FONT FACE="Arial, Helvetica">local_name</FONT>
is given, then a <FONT FACE="Arial, Helvetica">pragma</FONT> Discard_Names
is a representation pragma.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<DIV Class="Normal"> If the pragma applies to an enumeration type,
then the semantics of the Wide_Image and Wide_Value attributes are implementation
defined for that type; [the semantics of Image and Value are still defined
in terms of Wide_Image and Wide_Value.] In addition, the semantics of
Text_IO.Enumeration_IO are implementation defined. If the pragma applies
to a tagged type, then the semantics of the Tags.Expanded_Name function
are implementation defined for that type. If the pragma applies to an
exception, then the semantics of the Exceptions.Exception_Name function
are implementation defined for that exception.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Implementation defined: </B>The
semantics of pragma Discard_Names.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>The Width
attribute is still defined in terms of Image.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7.c</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>The semantics of S'Wide_Image
and S'Wide_Value are implementation defined for any subtype of an enumeration
type to which the pragma applies. (The pragma actually names the first
subtype, of course.) </FONT></DIV>
<H4 ALIGN=CENTER>Implementation Advice</H4>
<DIV Class="Paranum"><FONT SIZE=-2>8</FONT></DIV>
<DIV Class="Normal"> If the pragma applies to an entity, then the implementation
should reduce the amount of storage used for storing names associated
with that entity. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Reason: </B>A typical implementation
of the Image attribute for enumeration types is to store a table containing
the names of all the enumeration literals. Pragma Discard_Names allows
the implementation to avoid storing such a table without having to prove
that the Image attribute is never used (which can be difficult in the
presence of separate compilation).</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>We did not specify the semantics
of the Image attribute in the presence of this pragma because different
semantics might be desirable in different situations. In some cases,
it might make sense to use the Image attribute to print out a useful
value that can be used to identify the entity given information in compiler-generated
listings. In other cases, it might make sense to get an error at compile
time or at run time. In cases where memory is plentiful, the simplest
implementation makes sense: ignore the pragma. Implementations that are
capable of avoiding the extra storage in cases where the Image attribute
is never used might also wish to ignore the pragma.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8.c</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>The same applies to the Tags.Expanded_Name
and Exceptions.Exception_Name functions. </FONT></DIV>
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