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* ir.texi: Improve documentation for TARGET_EXPR.

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From-SVN: r29688
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Mark Mitchell 1999-09-28 07:40:15 +00:00 committed by Mark Mitchell
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2 changed files with 20 additions and 10 deletions
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gcc/cp/ChangeLog
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@ -1,3 +1,7 @@
1999-09-28 Mark Mitchell <mark@codesourcery.com>
* ir.texi: Improve documentation for TARGET_EXPR.
1999-09-27 Nathan Sidwell <nathan@acm.org>
Augment stringification of trees.

26
gcc/cp/ir.texi
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@ -1624,7 +1624,7 @@ These nodes represent @code{throw} expressions. The single operand is
an expression for the code that should be executed to throw the
exception. However, there is one implicit action not represented in
that expression; namely the call to @code{__throw}. This function takes
no arguments. If @code{setjmp}/@code{longjmp} exceptiosn are used, the
no arguments. If @code{setjmp}/@code{longjmp} exceptions are used, the
function @code{__sjthrow} is called instead. The normal G++ back-end
uses the function @code{emit_throw} to generate this code; you can
examine this function to see what needs to be done.
@ -1811,17 +1811,23 @@ is a @code{VAR_DECL} for the temporary variable. The second operand is
the initializer for the temporary. The initializer is evaluated, and
copied (bitwise) into the temporary.
Often, a @code{TARGET_EXPR} occurs on the right-hand side of an
assignment, or as the second operand to a comma-expression which is
itself the right-hand side of an assignment, etc. In this case, we say
that the @code{TARGET_EXPR} is ``normal''; otherwise, we say it is
``orphaned''. For a normal @code{TARGET_EXPR} the temporary variable
should be treated as an alias for the left-hand side of the assignment,
rather than as a new temporary variable.
The third operand to the @code{TARGET_EXPR}, if present, is a
cleanup-expression (i.e., destructor call) for the temporary. If this
expression is not copied into some other location (i.e., if it is not
the right-hand side of an assignment, or the second operand to a
comma-expression which is itself the right-hand side of an assignment,
etc.), then this expression must be executed when the statement
containing this expression is complete. These cleanups must always be
executed in the order opposite to that in which they were encountered.
Note that if a temporary is created on one branch of a conditional
operator (i.e., in the second or third operand to a @code{COND_EXPR}),
the cleanup must be run only if that branch is actually executed.
expression is orphaned, then this expression must be executed when the
statement containing this expression is complete. These cleanups must
always be executed in the order opposite to that in which they were
encountered. Note that if a temporary is created on one branch of a
conditional operator (i.e., in the second or third operand to a
@code{COND_EXPR}), the cleanup must be run only if that branch is
actually executed.
See @code{STMT_IS_FULL_EXPR_P} for more information about running these
cleanups.