forked from Alepha/Alepha
First draft of more streamlined tagged Exceptions.
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329
Exception.h
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329
Exception.h
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static_assert( __cplusplus > 2020'00 );
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#pragma once
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#include <Alepha/Alepha.h>
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#include <cstdlib>
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#include <string>
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#include <exception>
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#include <string_view>
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#include <typeindex>
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namespace Alepha::Hydrogen
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{
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namespace detail::exceptions::inline exports
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{
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/*!
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* @file
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*
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* Exception grades.
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*
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* In Alepha, there are several "grades" of exception types which can be thrown. The grade of
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* an exception is "branded" into its name as the last word in camel case.
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*
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* * `Throwable`: All exceptions inherit from this interface. Catching this will
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* catch anything which is part of this system. Normally you just ignore this grade.
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*
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* * `Notification`: When a thread is cancelled using interrupts, all exceptions thrown
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* to do so are derived from this type. Alepha threads are setup to catch and discard
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* exceptions of this grade in the thread start function.
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*
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* * `Exception`: This is the exception grade you would typically want to recover from.
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* Catch this grade, typically. They should contain sufficient information in their
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* data pack to facilitate a proper programmatic recovery. All exceptions of this grade
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* will also have `std::exception` as one of its bases, thus code which is unaware of
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* Alepha exceptions, but handles basic standard exceptions cleanly, will work just fine.
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*
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* * `Error`: This exception grade represents a form of moderately-unrecoverable condition.
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* The `Error` grade typically indicates a condition that prevents the current thread or
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* program state from being easily transitioned to a recovered state. However, a very
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* large state transform, such as a top-of-thread-callstack handler, may be able to
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* recover. For example, no more available operating system file handles. Tearing down
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* several client handlers in a multi-client server might alleviate this condition.
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*
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* * `Violation`: This exception grade represents an impossible to recover from condition.
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* Think of the handler for `Violation` as-if it were a `[[noreturn]]` function. Catch
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* handlers for this grade should only clean up resources which might cause persistent
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* state corruption. A program probably SHOULD ignore these and allow a core dump to
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* be emitted. An example of this might be: Runtime detection of dereference of a
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* raw pointer set to `nullptr`. This would typically indicate some kind of program
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* bug. `Violation::~Violation` is setup to call `abort()` when called.
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*/
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class Throwable
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{
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public:
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virtual ~Throwable()= default;
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virtual const char *message() const noexcept= 0;
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template< typename Target >
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const Target &
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as() const
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{
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if( not is_a< const Target * >() )
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{
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// TODO: Structured exception recovery here...
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}
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return dynamic_cast< const Target & >( *this );
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}
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template< typename Target >
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bool
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is_a() const noexcept
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{
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return dynamic_cast< const Target * >( this );
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}
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};
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class AnyTaggedThrowable
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: virtual public Throwable
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{
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public:
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virtual std::type_index tag() const noexcept= 0;
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};
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template< typename Tag >
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class TaggedThrowable
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: virtual public AnyTaggedThrowable
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{
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public:
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std::type_index
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tag() const noexcept final
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{
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return typeid( std::type_identity< Tag > );
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}
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};
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template< typename ... Bases >
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struct bases : virtual public Bases... {};
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// `Notification`s are "events" or "interrupts" that
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// if ignored will gracefully terminate the current
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// thread, but not halt the program.
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class Notification : public virtual Throwable {};
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class AnyTaggedNotification
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: public virtual bases< Notification, AnyTaggedThrowable > {};
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template< typename tag >
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class TaggedNotification
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: public virtual bases< TaggedThrowable< tag >, AnyTaggedNotification > {};
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using Interrupt= Notification;
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using AnyTaggedInterrupt= AnyTaggedNotification;
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template< typename tag >
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using TaggedInterrupt= TaggedNotification< tag >;
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// `Exception`s are recoverable at any point.
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class ExceptionBridgeInterface
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{
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public:
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virtual ~ExceptionBridgeInterface()= default;
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virtual const char *what() const noexcept= 0;
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};
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class Exception : virtual public bases< Throwable >, virtual private ExceptionBridgeInterface { public: using ExceptionBridgeInterface::what; };
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class AnyTaggedException : virtual public bases< Exception, AnyTaggedThrowable > {};
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template< typename tag >
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class TaggedException : virtual public bases< TaggedThrowable< tag >, AnyTaggedException > {};
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// `Error`s are only really recoverable by terminating
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// the major procedure underway. Like terminating the
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// entire thread or similar. Essentially, arbitrarily
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// localized recovery is impossible.
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class Error: virtual public bases< Throwable > {};
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class AnyTaggedError : virtual public bases< Error, AnyTaggedThrowable > {};
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template< typename tag >
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class TaggedError : virtual bases< AnyTaggedError, TaggedThrowable< tag > > {};
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// `Violation`s are unrecoverable events which happen to
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// the process. They are impossible to recover from.
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// Handlers for this should be treated almost like
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// `[[noreturn]]` functions. Mostly one would catch
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// this class if they intended to perform a bit of local
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// persistent state sanitization and then continue the
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// unwind process
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class Violation
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: virtual public bases< Throwable >
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{
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private:
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bool active= true;
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public:
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~Violation() override { if( not active ) abort(); }
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Violation( const Violation © )= delete;
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Violation( Violation © ) : active( copy.active ) { copy.active= false; }
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};
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class AnyTaggedViolation : virtual public bases< Violation, AnyTaggedThrowable > {};
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template< typename tag >
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class TaggedViolation : virtual public bases< AnyTaggedViolation, TaggedThrowable< tag > > {};
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template< typename T >
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concept DerivedFromException= std::is_base_of_v< Exception, T >;
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class NamedResourceThrowable
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: public virtual bases< Throwable >
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{
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public:
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virtual std::string_view resourceName() const noexcept= 0;
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};
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class AnyTaggedNamedResourceThrowable
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: virtual public bases< NamedResourceThrowable, AnyTaggedThrowable > {};
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template< typename tag >
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class TaggedNamedResourceThrowable
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: virtual public bases< AnyTaggedNamedResourceThrowable, TaggedThrowable< tag > > {};
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class NamedResourceNotification
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: public virtual bases< Notification, NamedResourceThrowable > {};
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class AnyTaggedNamedResourceNotification
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: public virtual bases< NamedResourceNotification, AnyTaggedNotification, AnyTaggedNamedResourceThrowable > {};
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template< typename tag >
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class TaggedNamedResourceNotification
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: public virtual bases< AnyTaggedNamedResourceNotification, TaggedNotification< tag >, TaggedNamedResourceThrowable< tag > > {};
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class NamedResourceException
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: public virtual bases< Exception, NamedResourceThrowable > {};
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class AnyTaggedNamedResourceException
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: public virtual bases< NamedResourceException, AnyTaggedException, AnyTaggedNamedResourceThrowable > {};
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template< typename tag >
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class TaggedNamedResourceException
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: public virtual bases< AnyTaggedNamedResourceException, TaggedException< tag >, TaggedNamedResourceThrowable< tag > > {};
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class NamedResourceError
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: public virtual bases< Error, NamedResourceThrowable > {};
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class AnyTaggedNamedResourceError
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: public virtual bases< NamedResourceError, AnyTaggedError, AnyTaggedNamedResourceThrowable > {};
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template< typename tag >
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class TaggedNamedResourceError
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: public virtual bases< AnyTaggedNamedResourceError, TaggedError< tag >, TaggedNamedResourceThrowable< tag > > {};
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class NamedResourceViolation
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: public virtual bases< Violation, NamedResourceThrowable > {};
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class AnyTaggedNamedResourceViolation
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: public virtual bases< NamedResourceViolation, AnyTaggedViolation, AnyTaggedNamedResourceThrowable > {};
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template< typename tag >
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class TaggedNamedResourceViolation
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: public virtual bases< AnyTaggedNamedResourceViolation, TaggedViolation< tag >, TaggedNamedResourceThrowable< tag > > {};
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class AllocationThrowable
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: public virtual bases< Throwable >
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{
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public:
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virtual std::size_t allocationAmount() const noexcept= 0;
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};
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class AnyTaggedAllocationThrowable
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: public virtual bases< AllocationThrowable, AnyTaggedThrowable > {};
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template< typename tag >
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class TaggedAllocationThrowable
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: public virtual bases< AnyTaggedAllocationThrowable, TaggedThrowable< tag > > {};
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class AllocationException
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: virtual public bases< Exception, AllocationThrowable > {};
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class AnyTaggedAllocationException
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: virtual public bases< AllocationException, AnyTaggedAllocationThrowable, AnyTaggedException > {};
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template< typename tag >
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class TaggedAllocationException
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: virtual public bases< AnyTaggedAllocationException, TaggedAllocationThrowable< tag >, TaggedException< tag > > {};
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class AllocationError
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: virtual public bases< Error, AllocationThrowable > {};
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class AnyTaggedAllocationError
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: virtual public bases< AllocationError, AnyTaggedAllocationThrowable, AnyTaggedError > {};
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template< typename tag >
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class TaggedAllocationError
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: virtual public bases< AnyTaggedAllocationError, TaggedAllocationThrowable< tag >, TaggedError< tag > > {};
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class AllocationViolation
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: virtual public bases< Violation, AllocationThrowable > {};
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class AnyTaggedAllocationViolation
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: virtual public bases< AllocationViolation, AnyTaggedAllocationThrowable, AnyTaggedViolation > {};
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template< typename tag >
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class TaggedAllocationViolation
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: virtual public bases< AnyTaggedAllocationViolation, TaggedAllocationThrowable< tag >, TaggedViolation< tag > > {};
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class MessageStorage
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: virtual public Throwable
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{
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private:
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std::string storage;
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public:
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explicit MessageStorage( std::string storage ) : storage( std::move( storage ) ) {}
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const char *message() const noexcept { return storage.c_str(); }
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};
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class AllocationAmountStorage
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: virtual public AllocationThrowable
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{
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private:
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std::size_t storage;
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public:
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std::size_t allocationAmount() const noexcept final { return storage; }
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};
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class AllocationExceptionBridge
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: virtual public std::bad_alloc, public virtual ExceptionBridgeInterface, virtual public Exception
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{
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public:
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const char *what() const noexcept override { return message(); }
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};
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class RegularExceptionBridge
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: virtual public std::exception, public virtual ExceptionBridgeInterface, virtual public Exception
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{
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public:
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const char *what() const noexcept override { return message(); }
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};
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template< typename Kind >
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auto
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build_exception( std::string message )
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{
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if constexpr( false ) {}
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else if constexpr( std::is_base_of_v< AllocationException, Kind > )
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{
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class Exception
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: virtual public Kind, virtual private AllocationExceptionBridge, virtual private MessageStorage, virtual private AllocationAmountStorage
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{
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public:
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explicit Exception( std::string message ) : MessageStorage( std::move( message ) ) {}
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};
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return Exception{ std::move( message ) };
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}
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else if constexpr( std::is_base_of_v< Exception, Kind > )
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{
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class Exception
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: virtual public Kind, virtual private RegularExceptionBridge, virtual private MessageStorage
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{
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public:
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explicit Exception( std::string message ) : MessageStorage( std::move( message ) ) {}
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};
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return Exception{ std::move( message ) };
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}
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else if constexpr( true )
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{
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class Thrown
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: virtual public Kind, virtual private MessageStorage
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{
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explicit Thrown( std::string message ) : MessageStorage( std::move( message ) ) {}
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};
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return Thrown{ std::move( message ) };
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}
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}
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}
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inline namespace exports {}
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namespace exports::inline exceptions
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{
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using namespace detail::exceptions::exports;
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}
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}
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