oracular (3) error_handler.3erl.gz

NAME

       error_handler - Default system error handler.

DESCRIPTION

       This module defines what happens when certain types of errors occur.

EXPORTS

       raise_undef_exception(Module, Function, Args) -> no_return()

              Types:

                 Module = Function = atom()
                 Args = list()
                    A (possibly empty) list of arguments Arg1,..,ArgN

              Raises an undef exception with a stacktrace, indicating that Module:Function/N is undefined.

       undefined_function(Module, Function, Args) -> any()

              Types:

                 Module = Function = atom()
                 Args = list()
                    A (possibly empty) list of arguments Arg1,..,ArgN

              This  function is called by the runtime system if a call is made to Module:Function(Arg1,.., ArgN)
              and Module:Function/N is undefined. Notice that this function  is  evaluated  inside  the  process
              making the original call.

              This  function  first  attempts to autoload Module. If that is not possible, an undef exception is
              raised.

              If it is possible to load Module and function Function/N is exported, it is called.

              Otherwise,  if  function   '$handle_undefined_function'/2   is   exported,   it   is   called   as
              '$handle_undefined_function'(Function, Args).

          Warning:
              Defining  '$handle_undefined_function'/2 in ordinary application code is highly discouraged. It is
              very easy to make subtle errors that can take a long time to debug. Furthermore, none of the tools
              for    static    code   analysis   (such   as   Dialyzer   and   Xref)   supports   the   use   of
              '$handle_undefined_function'/2 and no such support will be added. Only  use  this  function  after
              having  carefully considered other, less dangerous, solutions. One example of potential legitimate
              use is creating stubs for other sub-systems during testing and debugging.

              Otherwise an undef exception is raised.

       undefined_lambda(Module, Fun, Args) -> term()

              Types:

                 Module = atom()
                 Fun = function()
                 Args = list()
                    A (possibly empty) list of arguments Arg1,..,ArgN

              This function is evaluated if a call is made to Fun(Arg1,.., ArgN) when the  module  defining  the
              fun is not loaded. The function is evaluated inside the process making the original call.

              If  Module  is  interpreted,  the  interpreter  is invoked and the return value of the interpreted
              Fun(Arg1,.., ArgN) call is returned.

              Otherwise, it returns, if possible, the value of apply(Fun, Args) after  an  attempt  is  made  to
              autoload Module. If this is not possible, the call fails with exit reason undef.

NOTES

       The  code  in  error_handler  is  complex.  Do  not change it without fully understanding the interaction
       between the error handler, the init process of the code server, and the I/O mechanism of the code.

       Code changes that seem small can cause a deadlock, as unforeseen consequences can occur. The use of input
       is dangerous in this type of code.