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lumiera_/src/lib/error.hpp
Ichthyostega 9cb0a9b680 Library: discontinue setting error flag from Exceptions (see #1341) 
While seemingly subtle, this is a ''deep change.''
Up to now, the project attempted to maintain two mutually disjoint
systems of error reporting: C-style error flags and C++ exceptions.
Most notably, an attempt was made to keep both error states synced.

During the recent integration efforts, this increasingly turned out
as an obstacle and source for insidious problems (like deadlocks).


As a resolve, hereby the relation of both systems is **clarified**:
 * C-style error flags shall only be set and used by C code henceforth
 * C++ exceptions can (optionally) be thrown by retrieving the C-style error code
 * but the opposite is now ''discontinued'' : Exceptions ''do not set'' the error flag anymore
2023-10-01 20:11:45 +02:00

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/*
ERROR.hpp - Lumiera Exception Interface (C++)
Copyright (C) Lumiera.org
2008,2010 Hermann Vosseler <Ichthyostega@web.de>
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of
the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/** @file error.hpp
** Lumiera error handling (C++ interface).
** This header declares the Lumiera exception hierarchy,
** plus some of the most commonly used error flag values.
** Within Lumiera, C-style error states and C++-style exceptions
** are tightly integrated. Creating an exception sets the error flag,
** and there are helpers available to throw an exception automatically
** when a unclear error state is detected.
**
** @see error-state.c
** @see error.hpp
**
*/
#ifndef LUMIERA_ERROR_HPP_
#define LUMIERA_ERROR_HPP_
#define _STDBOOL_H // prevent <atomic> from including stdbool.h
#include "include/logging.h"
#include "include/lifecycle.h"
#include "lib/error.h"
#include <exception>
#include <string>
namespace lumiera {
using std::string;
using CStr = const char*;
#define LERR_(_NAME_) LUMIERA_ERROR_##_NAME_
/** error-ID for unspecified exceptions */
LUMIERA_ERROR_DECLARE(EXCEPTION);
/**
* Interface and Base definition for all Lumiera Exceptions.
* Provides common operations for getting an diagnostic message
* and to obtaining the _root cause_ message, i.e. the message
* from the first exception encountered in a chain of exceptions.
*/
class Error
: public std::exception
{
lumiera_err const id_; ///< an LUMIERA_ERROR id, which is set as errorstate on construction
string msg_; ///< friendly message intended for users (to be localised)
string desc_; ///< detailed description of the error situation for the developers
mutable string what_; ///< buffer for generating the detailed description on demand
const string cause_; ///< description of first exception encountered in the chain
public:
virtual ~Error () noexcept { }; ///< this is an interface
Error (string description=""
,lumiera_err const id =LERR_(EXCEPTION)) noexcept;
Error (std::exception const& cause
,string description=""
,lumiera_err const id =LERR_(EXCEPTION)) noexcept;
Error (Error &&) = default;
Error (Error const&) = default;
Error& operator= (Error &&) = delete;
Error& operator= (Error const&) = delete;
/** std::exception interface : yield a diagnostic message */
virtual CStr
what () const noexcept override;
/** the internal Lumiera-error-ID
* (was set as C-errorstate in ctor) */
lumiera_err
getID () const noexcept
{
return id_;
}
/** extract the message to be displayed for the user */
string const&
getUsermsg () const noexcept
{
return msg_;
}
/** If this exception was caused by a chain of further exceptions,
* return the description of the first one registered in this throw sequence.
* This works only if every exceptions thrown as a consequence of another exception
* is properly constructed by passing the original exception to the constructor
* @return the description string, maybe empty (if there is no known root cause)
*/
string const&
rootCause () const noexcept
{
return cause_;
}
/** replace the previous or default friendly message for the user.
* @note to be localised / translated.
*/
Error&
setUsermsg (string const& newMsg) noexcept
{
msg_ = newMsg;
return *this;
}
/** give additional developer info. Typically used at intermediate handlers to add context. */
Error&
prependInfo (string const& text) noexcept
{
desc_.insert (0, text);
return *this;
}
private:
static const string
extractCauseMsg (std::exception const&) noexcept;
};
/* === Exception sub-categories === */
namespace error {
/** global function for handling unknown exceptions
* encountered at functions declaring not to throw
* this kind of exception. Basically, any such event
* can be considered a severe design flaw; we can just
* add some diagnostics prior to halting.
*/
void lumiera_unexpectedException () noexcept;
/** throw an error::Fatal indicating "assertion failure" */
void assertion_terminate (const string& location);
/* constants to be used as error IDs */
LUMIERA_ERROR_DECLARE (LOGIC ); ///< contradiction to internal logic assumptions detected
LUMIERA_ERROR_DECLARE (FATAL ); ///< unable to cope with, internal logic floundered
LUMIERA_ERROR_DECLARE (CONFIG ); ///< execution aborted due to misconfiguration
LUMIERA_ERROR_DECLARE (STATE ); ///< unforeseen internal state
LUMIERA_ERROR_DECLARE (FLAG ); ///< non-cleared lumiera errorstate from C code
LUMIERA_ERROR_DECLARE (INVALID ); ///< invalid input or parameters encountered
LUMIERA_ERROR_DECLARE (EXTERNAL ); ///< failure in external service the application relies on
LUMIERA_ERROR_DECLARE (ASSERTION); ///< assertion failure
/* generic error situations */
LUMIERA_ERROR_DECLARE (LIFECYCLE); ///< Lifecycle assumptions violated
LUMIERA_ERROR_DECLARE (WRONG_TYPE); ///< runtime type mismatch
LUMIERA_ERROR_DECLARE (ITER_EXHAUST); ///< end of sequence reached
LUMIERA_ERROR_DECLARE (CAPACITY); ///< predefined fixed storage capacity
LUMIERA_ERROR_DECLARE (INDEX_BOUNDS); ///< index out of bounds
LUMIERA_ERROR_DECLARE (BOTTOM_VALUE); ///< invalid or NIL value
LUMIERA_ERROR_DECLARE (UNCONNECTED); ///< missing connection
LUMIERA_ERROR_DECLARE (UNIMPLEMENTED);///< unimplemented feature
/**
* Derived specific exceptions within Lumiera's exception hierarchy.
*/
template<lumiera_err const& eID, class PAR =Error>
class LumieraError
: public PAR
{
public:
LumieraError (std::string description=""
,lumiera_err const id=eID) noexcept
: PAR{description, id? id:eID}
{ }
LumieraError (std::exception const& cause
,std::string description=""
,lumiera_err const id=eID) noexcept
: PAR{cause, description, id? id:eID}
{ }
};
//----CLASS-------------------ID--------------PARENT------
using Logic = LumieraError<LERR_(LOGIC)>;
using Fatal = LumieraError<LERR_(FATAL), Logic>;
using State = LumieraError<LERR_(STATE)>;
using Flag = LumieraError<LERR_(FLAG), State>;
using Invalid = LumieraError<LERR_(INVALID)>;
using Config = LumieraError<LERR_(CONFIG), Invalid>;
using External = LumieraError<LERR_(EXTERNAL)>;
/** install our own handler for undeclared exceptions. Will be
* called automatically ON_BASIC_INIT when linking exception.cpp */
void install_unexpectedException_handler();
/** @return error detail-info if currently set, a default message else */
CStr detailInfo();
} // namespace error
/**
* Check the lumiera error state, which maybe was set by C-code.
* @throw Errorflag exception to signal an detected lumiera error
* @note specific error code and information is enclosed in
* the raised exception; the error state is \em not cleared.
*/
inline void
throwOnError()
{
if (lumiera_err errorFlag =lumiera_error())
{
throw error::Flag( error::detailInfo()
, errorFlag);
} }
/** Check the lumiera error state and throw a specific exception
* in case a non-cleared errorflag is detected. No-op else.
* @throw instance of the lumiera::Error subclass provided as
* template parameter, containing an lumiera::error::Flag
* as root cause to denote the detected error-flag state.
*/
template<class EX>
inline void
maybeThrow (string description ="")
{
if (lumiera_err errorFlag =lumiera_error())
{
throw EX (error::Flag{error::detailInfo(), errorFlag}
,description);
} }
} // namespace lumiera
/**************************************************//**
* convenience shortcut for a sequence of catch blocks
* just logging and consuming an error. Typically
* this sequence will be used within destructors,
* which, by convention, must not throw
*/
#define ERROR_LOG_AND_IGNORE(_FLAG_,_OP_DESCR_) \
catch (std::exception& problem) \
{ \
const char* errID = lumiera_error(); \
WARN (_FLAG_, "%s failed: %s", _OP_DESCR_, problem.what()); \
TRACE (debugging, "Error flag was: %s", errID);\
} \
catch (...) \
{ \
const char* errID = lumiera_error(); \
ERROR (_FLAG_, "%s failed with unknown exception; " \
"error flag is: %s" \
, _OP_DESCR_, errID?errID:"??"); \
}
/******************************************************//**
* convenience shortcut to catch and absorb any exception,
* then returning a default value instead. This scheme is
* typically used within signal handlers in the GTK UI,
* since GTK (written in C) can not propagate exceptions
*/
#define ON_EXCEPTION_RETURN(_VAL_,_OP_DESCR_) \
catch (std::exception& problem) \
{ \
const char* errID = lumiera_error(); \
WARN (stage, "%s (Signal Handler) failed: %s",\
_OP_DESCR_, problem.what()); \
TRACE (debugging, "Error flag was: %s", errID); \
return (_VAL_); \
} \
catch (...) \
{ \
const char* errID = lumiera_error(); \
ERROR (stage, "(Signal Handler) %s failed with " \
"unknown exception; error flag is: %s" \
, _OP_DESCR_, errID?errID:"??"); \
return (_VAL_); \
}
/**************************************************//**
* if NoBug is used, redefine some macros
* to rather throw Lumiera Errors instead of aborting
*/
#if 0 ///////////////////////////////////TODO disabled for now. NoBug aborts are hard and may hold some locks. There are hooks to allow throwing from NoBug TODO use them....
#ifdef NOBUG_ABORT
#undef NOBUG_ABORT
#define LUMIERA_NOBUG_LOCATION \
std::string (NOBUG_BASENAME(__FILE__)) +":"+ NOBUG_STRINGIZE(__LINE__) + ", function " + __func__
#define NOBUG_ABORT \
lumiera::error::assertion_terminate (LUMIERA_NOBUG_LOCATION);
#endif
#endif
#endif // LUMIERA_ERROR_HPP_
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