11.3 Raise Statements
1
[A raise_statement raises
an exception.]
Syntax
2/2
{
AI95-00361-01}
raise_statement ::= raise;
| raise exception_name [with string_expression]; raise [exception_name];Legality Rules
3
The
name, if any, in a
raise_statement shall denote an exception.
{re-raise statement} A
raise_statement with no
exception_name
(that is, a
re-raise statement) shall be within a handler, but
not within a body enclosed by that handler.
Name Resolution Rules
3.1/2
{
AI95-00361-01}
The expression, if any,
in a raise_statement, is expected to be of
type String. Dynamic Semantics
4/2
{
AI95-00361-01}
{raise (an exception)} To
raise an exception is to raise a new occurrence of that exception[,
as explained in
11.4].
{execution
(raise_statement with an exception_name) [partial]} For
the execution of a
raise_statement with an
exception_name, the named exception
is raised.
[If a string_expression
is present, the expression is evaluated and
its value is associated with the exception occurrence.] {execution
(re-raise statement) [partial]} For the
execution of a re-raise statement, the exception occurrence that caused
transfer of control to the innermost enclosing handler is raised [again].
4.a.1/2
Proof: {
AI95-00361-01}
The definition of Exceptions.Exception_Message
includes a statement that the string is returned (see 11.4.1).
We describe the use of the string here so that we don't have an unexplained
parameter in this subclause.
4.a
Implementation Note: For a re-raise statement,
the implementation does not create a new Exception_Occurrence, but instead
propagates the same Exception_Occurrence value. This allows the original
cause of the exception to be determined.
Examples
5
Examples of raise
statements:
6/2
{
AI95-00433-01}
raise Ada.IO_Exceptions.Name_Error; --
see A.13
raise Queue_Error with "Buffer Full"; -- see 9.117
raise; -- re-raise the current exception
Wording Changes from Ada 83
7.a
The fact that the name
in a raise_statement has to denote an exception
is not clear from RM83. Clearly that was the intent, since the italicized
part of the syntax rules so indicate, but there was no explicit rule.
RM83-1.5(11) doesn't seem to give the italicized parts of the syntax
any force.
Extensions to Ada 95
7.b/2
{
AI95-00361-01}
{extensions to Ada 95} The
syntax of a raise_statement is extended to
include a string message. This is more convenient than calling Exceptions.Exception_Message
(exception_name'Identity, string_expression),
and should encourage the use of message strings when raising exceptions.
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