Jens Geyer created THRIFT-4562:
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Summary: Calling wrong exception CTOR leads to "call failed:
unknown result" instead of the real exception being thrown
Key: THRIFT-4562
URL: https://issues.apache.org/jira/browse/THRIFT-4562
Project: Thrift
Issue Type: Bug
Components: Delphi - Compiler
Reporter: Jens Geyer
h2. Problem
# In contrast to other languages, there is no real way to prevent Delphi from
inheriting unwanted CTORs.
# The generated code initializes an "exception factory" helper object used for
serializing the exception info over the wire. This helper object is
instantiated in two cases:
** a) in the CTORs that are defined in the exception class
** b) when a property setter is called on that instance
h2. Example
The following IDL:
{code:java}
exception ApiException {
1: string Msg
2: ErrorCode Error
}
{code}
results in this Delphi code:
{code:java}
TApiException = class(TException)
// ... some unrelevant details omitted ...
public
constructor Create; overload;
constructor Create( const AMsg: System.string; AError: TErrorCode); overload;
// ... more code ...
end;
{code}
Due to the inheritance from {{TException}} and finally {{System.Exception}}, a
bunch of other CTORs is inherited, such as:
{code:java}
constructor Create(const Msg: string);
{code}
>From this, a situation may arise, in which the developer instantiates the
>instance by calling one of the inherited CTORs (which do not intialize the
>Factory helper object), then raising the exception without assigning any other
>values via property setter.
Under these circumstances, the Factory helper object is left at its default
value of {{nil}}, hence no suitable information is written to the wire. As a
direct result, being unable to deserialize anything useful on return, the
client code will run into the default catcher code which raises an generic
TApplicationException with {{MissingResult}} code and the "call failed: unknown
result" message.
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