10.15.1 Exceptions

Exceptions in Poke are values of type Exception, which is a struct defined like this:

deftype Exception =
  struct
  {
    int<32> code;
    string msg;
  };

where code identifies the type of the exception, and msg is supposed to be a textual description of the exceptional situation.

You can use codes 255 and higher for your own exceptions. For example:

raise Exception { code = 255; msg = "double upset event" };

Exception codes in the range 0..254 are reserved for poke. These are used in predefined exceptions which are standard, and have specific meanings:

E_generic

Generic error.

E_out_of_bounds

Out of bounds exception. This can be raised when accessing containers, like arrays and strings.

E_eof

End of file exception. This can be raised when mapping in the IO space.

E_elem

Invalid element exception. This is can be raised when accessing union fields that do not exist.

E_constraint

Constraint violation exception. This is raised when a constraint exception fails while mapping or constructing a struct.

E_conv

Conversion exception. This can be raised while casting values.

E_map_bounds

Out of map bounds exception. This can be raised while modifying a mapped value in a way it would violate its declared boundary (like the size of a mapped array.)

E_map

No map exception. This is raised when trying to map a not mapped value.

E_div_by_zero

Division by zero exception.

E_no_ios

No IOS exception. This is raised when the IO space is accessed but there is no IO space.

E_no_return

No return exception. This is raised when the end of a void function is reached.

E_io

Generic IO exception.

E_io_flags

Invalid flags were tried while opening an IO device.

The exception codes of the standard exceptions are available in the form of EC_* variables. For example, this how you would raise an IO error with a particular message:

raise Exception { code = EC_io,
                   msg = "fluzo capacitator overheat impedes IO" }