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<H1> 13.14 Freezing Rules</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> This clause defines a place in the program text
where each declared entity becomes ``frozen.'' A use of an entity, such
as a reference to it by name, or (for a type) an expression of the type,
causes freezing of the entity in some contexts, as described below. The
Legality Rules forbid certain kinds of uses of an entity in the region
of text where it is frozen. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="Normal"> <A NAME="I4503"></A><A NAME="I4504"></A>The <I>freezing</I>
of an entity occurs at one or more places (<I>freezing points</I>) in
the program text where the representation for the entity has to be fully
determined. Each entity is frozen from its first freezing point to the
end of the program text (given the ordering of compilation units defined
in <A HREF="RM-10-1-4.html">10.1.4</A>). </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3/1</FONT></DIV>
<DIV Class="Normal"> <A NAME="I4505"></A>The end of a <FONT FACE="Arial, Helvetica">declarative_part</FONT>,
<FONT FACE="Arial, Helvetica">protected_body</FONT>, or a declaration
of a library package or generic library package, causes <I>freezing</I>
of each entity declared within it, except for incomplete types. <A NAME="I4506"></A>A
noninstance body other than a renames-as-body causes freezing of each
entity declared before it within the same <FONT FACE="Arial, Helvetica">declarative_part</FONT>.
</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>4/1</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> <A NAME="I4507"></A>A
construct that (explicitly or implicitly) references an entity can cause
the <I>freezing</I> of the entity, as defined by subsequent paragraphs.
<A NAME="I4508"></A>At the place where a construct causes freezing, each
<FONT FACE="Arial, Helvetica">name</FONT>, <FONT FACE="Arial, Helvetica">expression</FONT>,
<FONT FACE="Arial, Helvetica">implicit_dereference</FONT>, or <FONT FACE="Arial, Helvetica">range</FONT>
within the construct causes freezing: </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<UL Class="Bulleted" Style="margin-bottom: 0.3em"><LI TYPE=DISC><A NAME="I4509"></A>The occurrence of a <FONT FACE="Arial, Helvetica">generic_instantiation</FONT>
causes freezing; also, if a parameter of the instantiation is defaulted,
the <FONT FACE="Arial, Helvetica">default_expression</FONT> or <FONT FACE="Arial, Helvetica">default_name</FONT>
for that parameter causes freezing.</LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<UL Class="Bulleted" Style="margin-bottom: 0.3em"><LI TYPE=DISC><A NAME="I4510"></A>The occurrence of an <FONT FACE="Arial, Helvetica">object_declaration</FONT>
that has no corresponding completion causes freezing. </LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC><A NAME="I4511"></A>The declaration of a record extension
causes freezing of the parent subtype. </LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>8/1</FONT></DIV>
<DIV Class="Normal"> <A NAME="I4512"></A>A static expression causes
freezing where it occurs. <A NAME="I4513"></A>An object name or nonstatic
expression causes freezing where it occurs, unless the name or expression
is part of a <FONT FACE="Arial, Helvetica">default_expression</FONT>,
a <FONT FACE="Arial, Helvetica">default_name</FONT>, or a per-object
expression of a component's <FONT FACE="Arial, Helvetica">constraint</FONT>,
in which case, the freezing occurs later as part of another construct.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8.1/1</FONT></DIV>
<DIV Class="Normal"> <A NAME="I4514"></A>An implicit call freezes
the same entities that would be frozen by an explicit call. This is true
even if the implicit call is removed via implementation permissions.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8.2/1</FONT></DIV>
<DIV Class="Normal"> <A NAME="I4515"></A>If an expression is implicitly
converted to a type or subtype <I>T</I>, then at the place where the
expression causes freezing, <I>T</I> is frozen.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>9</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> The following rules
define which entities are frozen at the place where a construct causes
freezing: </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>10</FONT></DIV>
<UL Class="Bulleted" Style="margin-bottom: 0.3em"><LI TYPE=DISC><A NAME="I4516"></A>At the place where an expression causes
freezing, the type of the expression is frozen, unless the expression
is an enumeration literal used as a <FONT FACE="Arial, Helvetica">discrete_choice</FONT>
of the <FONT FACE="Arial, Helvetica">array_aggregate</FONT> of an <FONT FACE="Arial, Helvetica">enumeration_representation_clause</FONT>.
</LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>11</FONT></DIV>
<UL Class="Bulleted" Style="margin-bottom: 0.3em"><LI TYPE=DISC><A NAME="I4517"></A>At the place where a <FONT FACE="Arial, Helvetica">name</FONT>
causes freezing, the entity denoted by the <FONT FACE="Arial, Helvetica">name</FONT>
is frozen, unless the <FONT FACE="Arial, Helvetica">name</FONT> is a
<FONT FACE="Arial, Helvetica">prefix</FONT> of an expanded name; <A NAME="I4518"></A>at
the place where an object <FONT FACE="Arial, Helvetica">name</FONT> causes
freezing, the nominal subtype associated with the <FONT FACE="Arial, Helvetica">name</FONT>
is frozen. </LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>11.1/1</FONT></DIV>
<UL Class="Bulleted" Style="margin-bottom: 0.3em"><LI TYPE=DISC><A NAME="I4519"></A>At the place where an <FONT FACE="Arial, Helvetica">implicit_dereference</FONT>
causes freezing, the nominal subtype associated with the <FONT FACE="Arial, Helvetica">implicit_dereference</FONT>
is frozen.</LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>12</FONT></DIV>
<UL Class="Bulleted" Style="margin-bottom: 0.3em"><LI TYPE=DISC><A NAME="I4520"></A>At the place where a <FONT FACE="Arial, Helvetica">range</FONT>
causes freezing, the type of the <FONT FACE="Arial, Helvetica">range</FONT>
is frozen. </LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>13</FONT></DIV>
<UL Class="Bulleted" Style="margin-bottom: 0.3em"><LI TYPE=DISC><A NAME="I4521"></A>At the place where an <FONT FACE="Arial, Helvetica">allocator</FONT>
causes freezing, the designated subtype of its type is frozen. If the
type of the <FONT FACE="Arial, Helvetica">allocator</FONT> is a derived
type, then all ancestor types are also frozen. </LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>14</FONT></DIV>
<UL Class="Bulleted" Style="margin-bottom: 0.3em"><LI TYPE=DISC><A NAME="I4522"></A>At the place where a callable entity
is frozen, each subtype of its profile is frozen. If the callable entity
is a member of an entry family, the index subtype of the family is frozen.
<A NAME="I4523"></A>At the place where a function call causes freezing,
if a parameter of the call is defaulted, the <FONT FACE="Arial, Helvetica">default_expression</FONT>
for that parameter causes freezing. </LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>15</FONT></DIV>
<UL Class="Bulleted" Style="margin-bottom: 0.3em"><LI TYPE=DISC><A NAME="I4524"></A>At the place where a subtype is frozen,
its type is frozen. <A NAME="I4525"></A><A NAME="I4526"></A>At the place
where a type is frozen, any expressions or <FONT FACE="Arial, Helvetica">name</FONT>s
within the full type definition cause freezing; the first subtype, and
any component subtypes, index subtypes, and parent subtype of the type
are frozen as well. <A NAME="I4527"></A><A NAME="I4528"></A>For a specific
tagged type, the corresponding class-wide type is frozen as well. For
a class-wide type, the corresponding specific type is frozen as well.
</LI></UL>
<H4 ALIGN=CENTER>Legality Rules</H4>
<DIV Class="Paranum"><FONT SIZE=-2>16</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> The explicit declaration
of a primitive subprogram of a tagged type shall occur before the type
is frozen (see <A HREF="RM-3-9-2.html">3.9.2</A>). </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>17</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> A type shall be
completely defined before it is frozen (see <A HREF="RM-3-11-1.html">3.11.1</A>
and <A HREF="RM-7-3.html">7.3</A>).</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>18</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> The completion
of a deferred constant declaration shall occur before the constant is
frozen (see <A HREF="RM-7-4.html">7.4</A>).</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>19/1</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> An operational
or representation item that directly specifies an aspect of an entity
shall appear before the entity is frozen (see <A HREF="RM-13-1.html">13.1</A>).
</DIV>
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