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construct/include/ircd/exception.h

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11 KiB
C++

// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.
#pragma once
#define HAVE_IRCD_EXCEPTION_H
/// Forward declarations for boost::system because it is not included here.
namespace boost::system
{
struct error_code;
struct error_category;
struct system_error;
namespace errc {}
}
namespace ircd
{
struct exception; // Root exception
// util
bool system_category(const std::error_category &) noexcept;
bool system_category(const std::error_code &) noexcept;
bool system_category(const boost::system::error_code &) noexcept;
bool is(const std::error_code &, const std::errc &) noexcept;
bool is(const boost::system::error_code &, const std::errc &) noexcept;
std::error_code make_error_code(const int &code = errno) noexcept;
std::error_code make_error_code(const std::error_code &) noexcept;
std::error_code make_error_code(const std::system_error &) noexcept;
std::error_code make_error_code(const boost::system::error_code &) noexcept;
std::error_code make_error_code(const boost::system::system_error &) noexcept;
std::system_error make_system_error(const int &code = errno);
std::system_error make_system_error(const std::errc &);
std::system_error make_system_error(const std::error_code &);
std::system_error make_system_error(const boost::system::error_code &);
std::system_error make_system_error(const boost::system::system_error &);
template<class... args> std::exception_ptr make_system_eptr(args&&...);
template<class... args> [[noreturn]] void throw_system_error(args&&...);
template<class E, class... args> std::exception_ptr make_exception_ptr(args&&...);
string_view string(const mutable_buffer &, const std::error_code &);
string_view string(const mutable_buffer &, const std::system_error &);
string_view string(const mutable_buffer &, const boost::system::error_code &);
string_view string(const mutable_buffer &, const boost::system::system_error &);
std::string string(const std::error_code &);
std::string string(const std::system_error &);
std::string string(const boost::system::error_code &);
std::string string(const boost::system::system_error &);
}
/// The root exception type.
///
/// All exceptions in the project inherit from this type. We generally don't
/// have catch blocks on this type. Instead we use `ircd::error` to catch
/// project-specific exceptions. This gives us just a little more indirection
/// to play with before inheriting from std::exception.
///
/// Not all exceptions are from project developer's code, such as
/// `std::out_of_range`, etc. It's not necessarily bad to just catch
/// `std::exception` and we do it often enough, but be considerate.
///
/// Remember: Not all exceptions have to inherit from `std::exception` either.
/// We have only one example of this: ctx::terminated. To be sure nothing can
/// possibly get through you can `catch(...)` but with extreme care that you
/// are not discarding a termination which will hang the `ircd::ctx` you're on.
///
/// !!!
/// NOTE: CONTEXT SWITCHES CANNOT OCCUR INSIDE CATCH BLOCKS UNLESS YOU USE THE
/// MITIGATION TOOLS PROVIDED IN `ircd::ctx` WHICH RESULT IN THE LOSS OF THE
/// ABILITY TO RETHROW THE EXCEPTION (i.e `throw` statement). BEST PRACTICE
/// IS TO RETURN CONTROL FROM THE CATCH BLOCK BEFORE CONTEXT SWITCHING.
/// !!!
struct ircd::exception
:virtual std::exception
{
static constexpr const size_t &BUFSIZE
{
512UL
};
IRCD_OVERLOAD(generate_skip)
IRCD_OVERLOAD(hide_name)
protected:
char buf[BUFSIZE];
ssize_t generate(const char *const &name, const string_view &fmt, const va_rtti &ap) noexcept;
ssize_t generate(const string_view &fmt, const va_rtti &ap) noexcept;
public:
const char *what() const noexcept override;
exception(generate_skip_t = {}) noexcept;
exception(exception &&) = delete;
exception(const exception &) = delete;
exception &operator=(exception &&) = delete;
exception &operator=(const exception &) = delete;
~exception() noexcept;
};
/// Exception generator convenience macro
///
/// If you want to create your own exception type, you have found the right
/// place! This macro allows creating an exception in the the hierarchy.
///
/// To create an exception, invoke this macro in your header. Examples:
///
/// IRCD_EXCEPTION(ircd::exception, my_exception)
/// IRCD_EXCEPTION(my_exception, my_specific_exception)
///
/// Then your catch sequence can look like the following:
///
/// catch(const my_specific_exception &e)
/// {
/// log("something specifically bad happened: %s", e.what());
/// }
/// catch(const my_exception &e)
/// {
/// log("something generically bad happened: %s", e.what());
/// }
/// catch(const ircd::exception &e)
/// {
/// log("unrelated bad happened: %s", e.what());
/// }
/// catch(const std::exception &e)
/// {
/// log("unhandled bad happened: %s", e.what());
/// }
///
/// Remember: the order of the catch blocks is important.
///
#define IRCD_EXCEPTION(parent, name) \
struct name \
:parent \
{ \
template<class... args> \
[[gnu::noinline]] \
name(hide_name_t, const string_view &fmt, args&&... ap) noexcept \
:parent{generate_skip} \
{ \
generate(fmt, ircd::va_rtti{std::forward<args>(ap)...}); \
} \
\
template<class... args> \
[[gnu::noinline]] \
name(hide_name_t, const string_view &fmt = " ") noexcept \
:parent{generate_skip} \
{ \
generate(fmt, ircd::va_rtti{}); \
} \
\
template<class... args> \
[[gnu::noinline]] \
name(const string_view &fmt, args&&... ap) noexcept \
:parent{generate_skip} \
{ \
generate(#name, fmt, ircd::va_rtti{std::forward<args>(ap)...}); \
} \
\
template<class... args> \
[[gnu::noinline]] \
name(const string_view &fmt = " ") noexcept \
:parent{generate_skip} \
{ \
generate(#name, fmt, ircd::va_rtti{}); \
} \
\
[[using gnu: flatten, always_inline]] \
name(generate_skip_t) noexcept \
:parent{generate_skip} \
{ \
} \
};
/// Hides the name of the exception when generating a string
#define IRCD_EXCEPTION_HIDENAME(parent, name) \
struct name \
:parent \
{ \
template<class... args> \
[[gnu::noinline]] \
name(const string_view &fmt, args&&... ap) noexcept \
:parent{generate_skip} \
{ \
generate(fmt, ircd::va_rtti{std::forward<args>(ap)...}); \
} \
\
template<class... args> \
[[gnu::noinline]] \
name(const string_view &fmt = " ") noexcept \
:parent{generate_skip} \
{ \
generate(fmt, ircd::va_rtti{}); \
} \
\
[[using gnu: flatten, always_inline]] \
name(generate_skip_t = {}) noexcept \
:parent{generate_skip} \
{ \
} \
};
namespace ircd
{
/// Root error exception type. Inherit from this.
/// List your own exception somewhere else (unless you're overhauling libircd).
/// example, in your namespace:
///
/// IRCD_EXCEPTION(ircd::error, error)
///
IRCD_EXCEPTION(exception, error) // throw ircd::error("something bad")
IRCD_EXCEPTION(error, user_error) // throw ircd::user_error("something silly")
}
template<class E,
class... args>
inline std::exception_ptr
ircd::make_exception_ptr(args&&... a)
try
{
throw E{std::forward<args>(a)...};
}
catch(const E &)
{
return std::current_exception();
};
template<class... args>
inline void
ircd::throw_system_error(args&&... a)
{
throw make_system_error(std::forward<args>(a)...);
}
template<class... args>
inline std::exception_ptr
ircd::make_system_eptr(args&&... a)
{
return std::make_exception_ptr(make_system_error(std::forward<args>(a)...));
}
[[gnu::always_inline]]
inline
ircd::exception::exception(generate_skip_t)
noexcept
{
buf[0] = '\0';
}