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< font size = "7" > System Library</ font >
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< td >< a href = "../../../index.htm" > Boost Home</ a > < a href = "index.html" >
Library Home</ a > Tutorial < a href = "reference.html" >
Reference</ a ></ td >
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< i >< b > Contents</ b ></ i ></ td >
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< td width = "100%" bgcolor = "#E8F5FF" >
< a href = "#Introduction" > Introduction</ a >< br >
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< a href = "#Macros" > Macros</ a >< br >
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< a href = "#Deprecated-names" > Deprecated names</ a >< br >
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< a href = "#Breaking-changes" > Breaking changes</ a >< br >
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< a href = "#Header-error_code" > Header < boost/system/error_code.hpp> </ a >< br >
< a href = "#Class-error_category" > Class < code > error_category</ code ></ a >< br >
< a href = "#Class-error_category-synopsis" > Class < code > error_category</ code > synopsis</ a >< br >
< a href = "#Class-error_category-virtual-members" > Class < code > error_category</ code > virtual members</ a >< br >
< a href = "#Class-error_category-non-virtual-members" > Class < code > error_category</ code > non-virtual members</ a >< br >
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< a href = "#Class-error_category-non-member-functions" > Class < code > error_category</ code >
non-member functions</ a >< br >
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< a href = "#Class-error_category-predefined-objects" > Class < code > error_category</ code > predefined objects</ a >< br >
< a href = "#Class-error_code" > Class < code > error_code</ code ></ a >< br >
< a href = "#Class-error_code-synopsis" > Class < code > error_code</ code > synopsis</ a >< br >
< a href = "#Class-error_code-constructors" > Class < code > error_code</ code > constructors</ a >< br >
< a href = "#Class-error_code-modifiers" > Class < code > error_code</ code > modifiers</ a >< br >
< a href = "#Class-error_code-observers" > Class < code > error_code</ code > observers</ a >< br >
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< a href = "#Class-error_condition" > Class < code > error_condition</ code ></ a >< br >
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< a href = "#Class-error_condition-synopsis" > Class < code > error_condition</ code > synopsis</ a >< br >
< a href = "#Class-error_condition-constructors" > Class < code > error_condition</ code > constructors</ a >< br >
< a href = "#Class-error_condition-modifiers" > Class < code > error_condition</ code > modifiers</ a >< br >
< a href = "#Class-error_condition-observers" > Class < code > error_condition</ code > observers</ a >< br >
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< a href = "#throws-object" >< code > throws</ code > object</ a >< br >
< a href = "#Semantics-of-throws" > Semantics of < code > throws</ code > object</ a >< br >
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< a href = "#Non-member-functions" > Non-member functions</ a >< br >
< a href = "#Header-system_error" > Header < boost/system/system_error.hpp> </ a >< br >
< a href = "#Class-system_error" > Class < code > system_error</ code ></ a >< br >
</ td >
</ tr >
</ table >
< h2 >< a name = "Introduction" > Introduction</ a ></ h2 >
< p > This reference documentation describes components that
programs may use to report error conditions originating from the operating
system or other low-level application program interfaces.</ p >
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< p > Boost.System library components never change the value of < code >
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errno</ code > .</ p >
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< h2 >< a name = "Macros" > Macros</ a ></ h2 >
< p > Users may defined the following macros if desired. Sensible defaults are
provided, so users may ignore these macros if they prefer.</ p >
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< tr >
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< td height = "16" >< b >< i > Macro Name</ i ></ b ></ td >
< td height = "16" >< b >< i > Default</ i ></ b ></ td >
< td height = "16" >< b >< i > Effect if defined</ i ></ b ></ td >
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</ tr >
< tr >
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< td valign = "top" height = "64" >< code > BOOST_SYSTEM_DYN_LINK</ code ></ td >
< td valign = "top" height = "64" > Defined if < code > BOOST_ALL_DYN_LINK</ code > is defined,
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otherwise not defined.</ td >
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< td valign = "top" height = "64" > Boost.System library is dynamically linked. If not defined,
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static linking is assumed.</ td >
</ tr >
< tr >
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< td valign = "top" height = "47" >< code > BOOST_SYSTEM_NO_LIB</ code ></ td >
< td valign = "top" height = "47" > Defined if < code > BOOST_ALL_NO_LIB</ code > is defined,
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otherwise not defined.</ td >
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< td valign = "top" height = "47" > Boost.System library does not use the Boost auto-link
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facility.</ td >
</ tr >
< tr >
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< td valign = "top" height = "32" >< code > BOOST_SYSTEM_NO_DEPRECATED</ code ></ td >
< td valign = "top" height = "32" > Not defined.</ td >
< td valign = "top" height = "32" > Deprecated features are excluded.</ td >
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</ tr >
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</ table >
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< h2 >< a name = "Deprecated-names" > Deprecated names</ a ></ h2 >
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< p > In the process of adding Boost.System to C++0x standard library, the C++
committee changed some
names. To ease transition, Boost.System deprecates the old
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names, but continues to provide them unless macro < code > BOOST_SYSTEM_NO_DEPRECATED</ code >
is defined.</ p >
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< tr >
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< td >< b >< i > Old usage, now deprecated</ i ></ b ></ td >
< td >< b >< i > Replacement</ i ></ b ></ td >
</ tr >
< tr >
< td >< code > get_generic_category()</ code ></ td >
< td >< code > generic_category()</ code ></ td >
</ tr >
< tr >
< td >< code > get_system_category()</ code ></ td >
< td >< code > system_category()</ code ></ td >
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</ tr >
< tr >
< td >< code > namespace posix</ code ></ td >
< td >< code > namespace errc</ code ></ td >
</ tr >
< tr >
< td >< code > namespace posix_error</ code ></ td >
< td >< code > namespace errc</ code ></ td >
</ tr >
< tr >
< td >< code > enum posix_errno</ code ></ td >
< td >< code > enum errc_t</ code ></ td >
</ tr >
< tr >
< td >< code > get_posix_category()</ code ></ td >
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< td >< code > generic_category()</ code ></ td >
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</ tr >
< tr >
< td >< code > posix_category</ code ></ td >
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< td >< code > generic_category()</ code ></ td >
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</ tr >
< tr >
< td >< code > errno_ecat</ code ></ td >
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< td >< code > generic_category()</ code ></ td >
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</ tr >
< tr >
< td >< code > native_ecat</ code ></ td >
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< td >< code > system_category()</ code ></ td >
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</ tr >
</ table >
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< h2 >< a name = "Breaking-changes" > Breaking changes</ a ></ h2 >
< p > Two static consts are replaced by functions. These are breaking changes best
fixed by globally adding () to these names to turn them into function calls.</ p >
< table border = "1" cellpadding = "5" cellspacing = "1" style = "border-collapse: collapse" bordercolor = "#111111" >
< tr >
< td >< b >< i > Old usage, now broken</ i ></ b ></ td >
< td >< b >< i > Replacement</ i ></ b ></ td >
</ tr >
< tr >
< td >< code > generic_category</ code ></ td >
< td >< code > generic_category()</ code ></ td >
</ tr >
< tr >
< td >< code > system_category</ code ></ td >
< td >< code > system_category()</ code ></ td >
</ tr >
</ table >
< p > User-defined BOOST_POSIX_API and BOOST_WINDOWS_API macros are no longer supported.</ p >
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< h2 >< a name = "Header-error_code" > Header < boost/system/error_code.hpp> </ a ></ h2 >
< h3 > < boost/system/error_code.hpp> synopsis</ h3 >
< blockquote >
< pre > namespace boost
{
namespace system
{
class < a href = "#Class-error_category" > error_category</ a > ;
class < a href = "#Class-error_code" > error_code</ a > ;
class < a href = "#Class-error_condition" > error_condition</ a > ;
// "Concept" helpers
template< class T = "" >
struct is_error_code_enum { static const bool value = false; };
template< class T = "" >
struct is_error_condition_enum { static const bool value = false; };
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// generic error_conditions
namespace errc
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{
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enum errc_t
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{
success = 0,
address_family_not_supported, //EAFNOSUPPORT
address_in_use, //EADDRINUSE
address_not_available, //EADDRNOTAVAIL
already_connected, //EISCONN
argument_list_too_long, //E2BIG
argument_out_of_domain, //EDOM
bad_address, //EFAULT
bad_file_descriptor, //EBADF
bad_message, //EBADMSG
broken_pipe, //EPIPE
connection_aborted, //ECONNABORTED
connection_already_in_progress, //EALREADY
connection_refused, //ECONNREFUSED
connection_reset, //ECONNRESET
cross_device_link, //EXDEV
destination_address_required, //EDESTADDRREQ
device_or_resource_busy, //EBUSY
directory_not_empty, //ENOTEMPTY
executable_format_error, //ENOEXEC
file_exists, //EEXIST
file_too_large, //EFBIG
filename_too_long, //ENAMETOOLONG
function_not_supported, //ENOSYS
host_unreachable, //EHOSTUNREACH
identifier_removed, //EIDRM
illegal_byte_sequence, //EILSEQ
inappropriate_io_control_operation,//ENOTTY
interrupted, //EINTR
invalid_argument, //EINVAL
invalid_seek, //ESPIPE
io_error, //EIO
is_a_directory, //EISDIR
message_size, //EMSGSIZE
network_down, //ENETDOWN
network_reset, //ENETRESET
network_unreachable, //ENETUNREACH
no_buffer_space, //ENOBUFS
no_child_process, //ECHILD
no_link, //ENOLINK
no_lock_available, //ENOLCK
no_message_available, //ENODATA
no_message, //ENOMSG
no_protocol_option, //ENOPROTOOPT
no_space_on_device, //ENOSPC
no_stream_resources, //ENOSR
no_such_device_or_address, //ENXIO
no_such_device, //ENODEV
no_such_file_or_directory, //ENOENT
no_such_process, //ESRCH
not_a_directory, //ENOTDIR
not_a_socket, //ENOTSOCK
not_a_stream, //ENOSTR
not_connected, //ENOTCONN
not_enough_memory, //ENOMEM
not_supported, //ENOTSUP
operation_canceled, //ECANCELED
operation_in_progress, //EINPROGRESS
operation_not_permitted, //EPERM
operation_not_supported, //EOPNOTSUPP
operation_would_block, //EWOULDBLOCK
owner_dead, //EOWNERDEAD
permission_denied, //EACCES
protocol_error, //EPROTO
protocol_not_supported, //EPROTONOSUPPORT
read_only_file_system, //EROFS
resource_deadlock_would_occur, //EDEADLK
resource_unavailable_try_again, //EAGAIN
result_out_of_range, //ERANGE
state_not_recoverable, //ENOTRECOVERABLE
stream_timeout, //ETIME
text_file_busy, //ETXTBSY
timed_out, //ETIMEDOUT
too_many_files_open_in_system, //ENFILE
too_many_files_open, //EMFILE
too_many_links, //EMLINK
too_many_synbolic_link_levels, //ELOOP
value_too_large, //EOVERFLOW
wrong_protocol_type //EPROTOTYPE
};
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} // namespace errc
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template< > struct is_error_condition_enum< posix::posix_errno > < errc::errc_t>
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{ static const bool value = true; };
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// < a href = "#Non-member-functions" > non-member functions</ a >
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bool operator==( const error_code & lhs, const error_code & rhs );
bool operator==( const error_code & code, const error_condition & condition );
bool operator==( const error_condition & condition, const error_code & code );
bool operator==( const error_condition & lhs, const error_condition & rhs );
bool operator!=( const error_code & lhs, const error_code & rhs );
bool operator!=( const error_code & code, const error_condition & condition );
bool operator!=( const error_condition & condition, const error_code & code );
bool operator!=( const error_condition & lhs, const error_condition & rhs );
bool operator< ( const error_code & lhs, const error_code & rhs );
bool operator< ( const error_condition & lhs, const error_condition & rhs );
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error_code make_error_code( errc::errc_t e );
error_condition make_error_condition( errc::errc_t e );
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template < class charT, class traits>
std::basic_ostream< charT,traits>&
operator<< ( basic_ostream< charT,traits>& os, const error_code & ec );
size_t hash_value( const error_code & ec );
}
}</ pre >
</ blockquote >
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< p > The value of each< code > errc_t</ code > constant shall be the same as the
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value of the < code > < cerrno> </ code > macro shown in the above synopsis.</ p >
< p > Users may specialize < code > is_error_code_enum</ code > and < code >
is_error_condition_enum</ code > templates to indicate that a type is eligible for
class < code > error_code</ code > and < code > error_condition</ code > automatic
conversions respectively.</ p >
< h2 >< a name = "Class-error_category" > Class < code > error_category</ code ></ a ></ h2 >
< p > The class < code > error_category</ code > defines the base class for types used
to identify the source and encoding of a particular category of error code.</ p >
< p >< i > [Note:</ i > Classes may be derived from < code > error_category</ code >
to support additional categories of errors. < i > --end note]</ i ></ p >
< p > The class < code > error_category</ code > serves as a base class for types used
to identify the source and encoding of a particular category of error code.
Classes may be derived from < code > error_category</ code > to support categories of
errors in addition to those defined in the Boost System library. Such classes
shall behave as specified in this subclause. [< i > Note:</ i > < code > error_category</ code >
objects are passed by reference, and two such objects are equal if they have the
same address. This means that applications using custom < code > error_category</ code >
types should create a single object of each such type. < i > —end note</ i > ]</ p >
< h3 >< a name = "Class-error_category-synopsis" > Class < code > error_category</ code > synopsis</ a ></ h3 >
< blockquote >
< pre > namespace boost
{
namespace system
{
class error_category : public noncopyable
{
public:
virtual ~error_category();
virtual const char * name() const = 0;
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virtual string message( int ev ) const = 0;
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virtual error_condition default_error_condition( int ev ) const;
virtual bool equivalent( int code, const error_condition & condition ) const;
virtual bool equivalent( const error_code & code, int condition ) const;
bool operator==( const error_category & rhs ) const;
bool operator!=( const error_category & rhs ) const;
bool operator< ( const error_category & rhs ) const;
};
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const error_category & system_category();
const error_category & generic_category();
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}
}</ pre >
</ blockquote >
< h3 >< a name = "Class-error_category-virtual-members" > Class < code > error_category</ code > virtual members</ a ></ h3 >
< p > Classes derived from < code > error_category</ code > shall behave as specified in
this subclause.</ p >
< pre > virtual const char * name() const=0;</ pre >
< blockquote >
< p >< i > Returns: </ i > a string naming the error category.</ p >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
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< pre > virtual string message( int ev ) const=0;</ pre >
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< blockquote >
< p >< i > Returns:</ i > A string that describes the error denoted by
< code > ev</ code > .</ p >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< p >< code > virtual error_condition default_error_condition( int ev ) const;</ code ></ p >
< blockquote >
< p >< i > Returns:</ i > < code > error_condition( ev, *this )</ code > .</ p >
< blockquote >
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< p dir = "ltr" > [< i > --Note:</ i > Derived classes will typically convert < code > ev</ code >
to some portable < code > error_category</ code > , such as < code > generic_category()</ code > ,
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and return it as an < code > error_condition</ code > for that category. < i > --end
note</ i > ]</ p >
</ blockquote >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< p >< code > virtual bool equivalent( int code, const error_condition &
condition )
const;</ code ></ p >
< blockquote >
< p >< i > Returns:</ i > < code > default_error_condition( code ) == condition</ code > .</ p >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< p >< code > virtual bool equivalent( const error_code & code, int condition ) const;</ code ></ p >
< blockquote >
< p >< i > Returns:</ i > < code > *this == code.category() && code.value() == condition</ code > .</ p >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< h3 >< a name = "Class-error_category-non-virtual-members" > Class < code > error_category</ code > non-virtual members</ a ></ h3 >
< p >< code > bool operator==( const error_category & rhs ) const;</ code ></ p >
< blockquote >
< p >< i > Returns:</ i > < code > this == & rhs</ code > .</ p >
</ blockquote >
< p >< code > bool operator!=( const error_category & rhs ) const;</ code ></ p >
< blockquote >
< p >< i > Returns:</ i > < code > this != & rhs</ code > .</ p >
</ blockquote >
< pre > bool operator< ( const error_category & rhs ) const;</ pre >
< blockquote >
< p >< i > Returns:</ i > < code > std::less< const error_category*> ()( this, & rhs )</ code > .</ p >
< blockquote >
< p >< i > [Note:</ i > < code > std::less</ code > provides a total ordering for
pointers. < i > --end note]</ i ></ p >
</ blockquote >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
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< h3 >< a name = "Class-error_category-non-member-functions" > Class < code > error_category</ code >
non-member functions</ a ></ h3 >
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< pre > const error_category & system_category();</ pre >
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< blockquote >
< p >< i > Returns:</ i > A reference to a < code > error_category</ code > object
identifying errors originating from the operating system.</ p >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
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< pre > const error_category & generic_category();</ pre >
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< blockquote >
< p >< i > Returns:</ i > A reference to a < code > error_category</ code > object
identifying portable error conditions.</ p >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
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< h2 >< a name = "Class-error_code" > Class < code >
error_code</ code ></ a ></ h2 >
< p > The class < code > error_code</ code > describes an object used to hold error code
values, such as those originating from the operating< br >
system or other low-level application program interfaces. < i > [ Note: </ i > Class
< code > error_code</ code > is an adjunct to error reporting by< br >
exception. < i > —end note ]</ i ></ p >
< h3 >< a name = "Class-error_code-synopsis" > Class < code >
error_code</ code > synopsis</ a ></ h3 >
< blockquote >
< pre > namespace boost
{
namespace system
{
class error_code {
public:
// constructors:
error_code();
error_code( val, const error_category & cat );
template < class < code > ErrorCodeEnum</ code > >
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error_code(< code > ErrorCodeEnum</ code > e );
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// modifiers:
void assign( int val, const error_category & cat );
template< typename < code > ErrorCodeEnum</ code > >
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error_code & operator=( < code > ErrorCodeEnum</ code > val );;
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void clear();
// observers:
int value() const;
cont error_category & category() const;
error_condition default_error_condition() const;
string message() const;
operator unspecified-bool-type() const;
private:
int val_; // < i > exposition only</ i >
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const error_category * cat_; // < i > exposition only</ i >
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};
}
}</ pre >
</ blockquote >
< h3 >< a name = "Class-error_code-constructors" > Class < code >
error_code</ code > constructors</ a ></ h3 >
< pre > error_code();</ pre >
< blockquote >
< p >< i > Effects: </ i > Constructs an object of type < code > error_code</ code > .</ p >
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< p >< i > Postconditions:</ i > < code > val_ == 0 && cat_ == & system_category()</ code > .</ p >
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< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< pre > error_code( int val, const error_category & cat );</ pre >
< blockquote >
< p >< i > Effects: </ i > Constructs an object of type < code > error_code</ code > .</ p >
< p >< i > Postconditions:</ i > < code > val_ == val && cat_ == & cat</ code > .</ p >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< pre > template < class < code > ErrorCodeEnum</ code > >
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error_code(< code > ErrorCodeEnum</ code > val );</ pre >
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< blockquote >
< p >< i > Effects: </ i > Constructs an object of type < code > error_code</ code > .</ p >
< p >< i > Postconditions:</ i > < code > *this == make_error_code( val )</ code > .</ p >
< p >< i > Throws:</ i > Nothing.</ p >
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< p >< i > Remarks:</ i > This constructor shall not participate in overload
resolution unless < code > is_error_code_enum< ErrorCodeEnum> ::value</ code > is
< code > true</ code > .</ p >
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</ blockquote >
< h3 >< a name = "Class-error_code-modifiers" > Class < code >
error_code</ code > modifiers</ a ></ h3 >
< pre > void assign( int val, const error_category & cat );</ pre >
< blockquote >
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< p >< i > Postconditions:</ i > < code > val_ == val && cat_ == & cat</ code > .</ p >
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< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< pre > template< typename < code > ErrorCodeEnum</ code > >
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error_code & operator=( < code > ErrorCodeEnum</ code > val );</ pre >
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< blockquote >
< p >< i > Postconditions:</ i > < code > *this == make_error_code( val )</ code > .</ p >
< p >< i > Throws:</ i > Nothing.</ p >
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< p >< i > Remarks:</ i > This operator shall not participate in overload resolution
unless < code > is_error_code_enum< ErrorCodeEnum> ::value</ code > is < code > true</ code > .</ p >
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</ blockquote >
< p >< code > void clear();</ code ></ p >
< blockquote >
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< p >< i > postcondition:</ i > < code > value() == 0 && category() ==
system_category()</ code ></ p >
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</ blockquote >
< h3 >< a name = "Class-error_code-observers" > Class < code >
error_code</ code > observers</ a ></ h3 >
< p >< code > int value() const;</ code ></ p >
< blockquote >
< p >< i > Returns:</ i > < code > val_</ code > .</ p >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
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< p >< code > const error_category & category() const;</ code ></ p >
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< blockquote >
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< p >< i > Returns:</ i > < code > *cat_</ code > .</ p >
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< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< pre > error_condition default_error_condition() const;</ pre >
< blockquote >
< p >< i > Returns:</ i > < code > category().default_error_condition( value())</ code > .</ p >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< p >< code > string message() const;</ code ></ p >
< blockquote >
< p >< i > Returns:</ i > < code > category().message( value())</ code > .</ p >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< p >< code > operator < i > unspecified-bool-type</ i > () const;</ code ></ p >
< blockquote >
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< p >< i > Returns:</ i > if < code > value() != 0</ code > , returns a value that will evaluate
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< code > true</ code > in a boolean context; otherwise, returns a value that will
evaluate < code > false</ code > in a boolean context. The value type returned shall
not be convertible to < code > int</ code > .</ p >
< p >< i > Throws:</ i > nothing.</ p >
< p >< i > [Note: </ i > This conversion can be used in contexts where a < code > bool</ code >
is expected ( e.g., an < code > if</ code > condition ); however, implicit conversions
( e.g., to < code > int</ code > ) that can occur with < code > bool</ code > are not
allowed, eliminating some sources of user error. One possible implementation
choice for this type is pointer-to-member. < i > --end note ]</ i ></ p >
</ blockquote >
< h2 >< a name = "Class-error_condition" > Class < code > error_condition</ code ></ a ></ h2 >
< p > The class < code > error_condition</ code > describes an object used to hold
values identifying error conditions. < i > [ Note: </ i >< code > error_condition</ code >
values are portable abstractions, while < code > error_code</ code > values are
implementation specific. < i > --end note ]</ i ></ p >
< h3 >< a name = "Class-error_condition-synopsis" > Class < code > error_condition</ code > synopsis</ a ></ h3 >
< blockquote >
< pre > namespace boost
{
namespace system
{
class error_condition
{
public:
// constructors:
error_condition();
error_condition( int val, const error_category & cat );
template < class ErrorConditionEnum>
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error_condition( errorConditionEnum val );
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// modifiers:
void assign( int val, const error_category & cat );
template< typename ErrorConditionEnum>
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error_condition & operator=( ErrorConditionEnum val );
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void clear();
// observers:
int value() const;
const error_category & category() const;
string message() const;
operator unspecified-bool-type () const;
private:
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int val_; // < i > exposition only</ i >
const error_category * cat_; // < i > exposition only</ i >
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};
}
}</ pre >
</ blockquote >
< h3 >< a name = "Class-error_condition-constructors" > Class < code > error_condition</ code >
constructors</ a ></ h3 >
< pre > error_condition(); </ pre >
< blockquote >
< p >< i > Effects:</ i > Constructs an object of type < code > error_condition</ code > .</ p >
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< p >< i > Postconditions:</ i > < code > val_ == 0 and cat_ == & generic_category()</ code > .</ p >
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< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
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< pre > error_condition( int val, const error_category & cat );</ pre >
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< blockquote >
< p >< i > Effects: </ i > Constructs an object of type error_condition.</ p >
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< p >< i > Postconditions:</ i > < code > val_ == val and cat_ == & cat</ code > .</ p >
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< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< pre > template < class ErrorConditionEnum>
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error_condition( ErrorConditionEnum e );</ pre >
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< blockquote >
< p >< i > Effects:</ i > Constructs an object of type < code > error_condition</ code > .</ p >
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< p >< i > Postconditions:</ i > < code > *this == make_error_condition(e)</ code > .</ p >
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< p >< i > Throws:</ i > Nothing.</ p >
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< p >< i > Remarks:</ i > This constructor shall not participate in overload
resolution unless < code > is_error_condition_enum< ErrorConditionEnum> ::value</ code >
is < code > true</ code > .</ p >
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</ blockquote >
< h3 >< a name = "Class-error_condition-modifiers" > Class < code > error_condition</ code >
modifiers</ a ></ h3 >
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< pre > void assign( int val, const error_category & cat ); </ pre >
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< blockquote >
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< p >< i > Postconditions:</ i > < code > val_ == val and cat_ == & cat</ code > . </ p >
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< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< pre > template< typename ErrorConditionEnum>
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error_condition & operator=( ErrorConditionEnum e );</ pre >
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< blockquote >
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< p >< i > Postconditions:</ i > < code > *this == make_error_condition( e )</ code > .</ p >
< p >< i > Returns:</ i > < code > *this</ code > .</ p >
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< p >< i > Throws:</ i > Nothing.</ p >
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< p >< i > Remarks:</ i > This operator shall not participate in overload resolution
unless < code > is_error_condition_enum< ErrorConditionEnum> ::value</ code > is
< code > true</ code > .</ p >
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</ blockquote >
< p >< code > void clear();</ code ></ p >
< blockquote >
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< p >< i > postcondition:</ i > < code > value() == 0 && category() == generic_category()</ code ></ p >
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</ blockquote >
< h3 >< a name = "Class-error_condition-observers" > Class < code > error_condition</ code >
observers</ a ></ h3 >
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< pre > int value() const;</ pre >
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< blockquote >
< p >< i > Returns:</ i > < code > val_</ code > .</ p >
< p >< i > Throws:</ i > Nothing</ p >
</ blockquote >
< pre > const error_category & category() const;</ pre >
< blockquote >
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< p >< i > Returns:</ i > < code > *cat_</ code > .</ p >
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< p > Throws: Nothing.</ p >
</ blockquote >
< pre > string message() const;</ pre >
< blockquote >
< p >< i > Returns:</ i > < code > category().message( value() )</ code > .</ p >
< p >< i > Throws:</ i > Nothing.</ p >
</ blockquote >
< pre > operator unspecified-bool-type () const;</ pre >
< blockquote >
< p >< i > Returns: </ i > If < code > value() != 0</ code > , returns a value that will
evaluate < code > true</ code > in a boolean context; otherwise, returns a value
that will evaluate < code > false</ code > . The return type shall not be
convertible to < code > int</ code > . </ p >
< p >< i > Throws:</ i > Nothing.</ p >
< p >< i > [ Note:</ i > This conversion can be used in contexts where a < code > bool</ code >
is expected ( e.g., an if condition ); however, implicit conversions ( e.g., to
< code > int</ code > ) that can occur with < code > bool</ code > are not allowed,
eliminating some sources of user error. One possible implementation choice for
this type is pointer to member. < i > --end note</ i > < i > ]</ i ></ p >
</ blockquote >
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< h2 >< a name = "throws-object" >< code > throws</ code > object</ a ></ h2 >
< pre > extern error_code throws;</ pre >
< p > The predefined < code > error_code</ code > object < code > throws</ code > is supplied
for use as a " throw on error" tag.</ p >
< h2 >< a name = "Semantics-of-throws" > Semantics of < code > throws</ code ></ a > object</ h2 >
< p > Functions that specify an argument in the form < code > error_code& ec=throws</ code > ,
with appropriate namespace qualifiers, have the following error handling
semantics:</ p >
< blockquote >
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< p >< i > Postconditions:</ i ></ p >
< blockquote >
< p > If < code > & ec != & throws</ code > and an error occurred:</ p >
< ul >
< li > < code > ec.value()</ code > returns the implementation specific error
number for the particular error that occurred.</ li >
< li >< code > ec.category()</ code > returns the < code >
< a href = "#Class-error_category" > error_category</ a ></ code > for < code > ec.value()</ code > .</ li >
</ ul >
< p > if < code > & ec != & throws</ code > and an error did not occur, < code > ec.clear()</ code > .</ p >
</ blockquote >
< p >< i > Throws:</ i ></ p >
< blockquote >
< p > If an error occurs and < code > & ec == & throws</ code > , throws an exception of type
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< code >< a href = "#Class-system_error" > system_error</ a ></ code > or of a type
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derived from < code >< a href = "#Class-system_error" > system_error</ a ></ code > . The
exception's < code > code()</ code > member function returns a reference to an
< code > error_code</ code > object with the behavior specified in < i >
Postconditions</ i > .</ p >
</ blockquote >
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</ blockquote >
< h2 >< a name = "Non-member-functions" > Non-member functions</ a ></ h2 >
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< pre > bool operator==( const error_code & lhs, const error_code & rhs );</ pre >
< blockquote >
< p >< i > Returns:</ i > < code > lhs.category() == rhs.category() && lhs.value() ==
rhs.value()</ code > .</ p >
< p >< i > Throws: </ i > Nothing.</ p >
</ blockquote >
< pre > bool operator==( const error_code & code, const error_condition & condition );
bool operator==( const error_condition & condition, const error_code & code );</ pre >
< blockquote >
< p >< i > Returns:</ i > < code > code.category().equivalent( code.value(), condition )< br >
|| condition.category().equivalent( code, condition.value() )</ code > .</ p >
< p >< i > Throws: </ i > Nothing.</ p >
</ blockquote >
< pre > bool operator==( const error_condition & lhs, const error_condition & rhs );</ pre >
< blockquote >
< p >< i > Returns:</ i > < code > lhs.category() == rhs.category() && lhs.value() ==
rhs.value()</ code > .</ p >
< p >< i > Throws: </ i > Nothing.</ p >
</ blockquote >
< pre > bool operator!=( const error_code & lhs, const error_code & rhs );</ pre >
< blockquote >
< p >< i > Returns:</ i > < code > !(lhs == rhs )</ code > .</ p >
< p >< i > Throws: </ i > Nothing.</ p >
</ blockquote >
< pre > bool operator!=( const error_code & code, const error_condition & condition );
bool operator!=( const error_condition & condition, const error_code & code );</ pre >
< blockquote >
< p >< i > Returns:</ i >< code > !( code == condition )</ code > .</ p >
< p >< i > Throws: </ i > Nothing.</ p >
</ blockquote >
< pre > bool operator!=( const error_condition & lhs, const error_condition & rhs );</ pre >
< blockquote >
< p >< i > Returns:</ i > < code > !(lhs == rhs )</ code > .</ p >
< p >< i > Throws: </ i > Nothing.</ p >
</ blockquote >
< pre > bool operator< ( const error_code & lhs, const error_code & rhs );</ pre >
< blockquote >
< p >< i > Returns:</ i > < code > lhs.category() < rhs.category()< br >
|| (lhs.category() == rhs.category() && lhs.value() < rhs.value())</ code > .</ p >
< p >< i > Throws: </ i > Nothing.</ p >
</ blockquote >
< pre > bool operator< ( const error_condition & lhs, const error_condition & rhs );</ pre >
< blockquote >
< p >< i > Returns:</ i > < code > lhs.category() < rhs.category()< br >
|| (lhs.category() == rhs.category() && lhs.value() < rhs.value())</ code > .</ p >
< p >< i > Throws: </ i > Nothing.</ p >
</ blockquote >
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< pre > error_code make_error_code( errc::errc_t e );</ pre >
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< blockquote >
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< p >< i > Returns:</ i > < code > error_code( e, generic_category())</ code > .</ p >
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</ blockquote >
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< pre > error_condition make_error_condition( errc::errc_t e );</ pre >
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< blockquote >
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< p >< i > Returns:</ i > < code > error_condition( static_cast< int> ( e ), generic_category())</ code > .</ p >
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</ blockquote >
< pre > template < class charT, class traits>
std::basic_ostream< charT,traits>&
operator<< ( basic_ostream< charT,traits>& os, const error_code & ec );</ pre >
< blockquote >
< p >< i > Effects:</ i > < code > os << ec.category().name() << ':' << ec.value()</ code > .</ p >
< p >< i > Returns:</ i > < code > os</ code > .</ p >
</ blockquote >
< pre > size_t < a name = "hash_value" > hash_value</ a > ( const error_code & ec );</ pre >
< blockquote >
< p >< i > Returns: </ i > A hash value representing < code > ec</ code > .</ p >
</ blockquote >
< h2 >< a name = "Header-system_error" > Header < boost/system/system_error.hpp> </ a ></ h2 >
< h3 >< a name = "Class-system_error" > Class < code >
system_error</ code ></ a ></ h3 >
< p > The class < code > system_error</ code > describes an exception object used to
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report errors that have an associated < code >< a href = "#Class-error_code" > error_code</ a ></ code > . Such errors typically originate from operating system or other low-level
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application program interfaces.</ p >
< blockquote >
< pre > namespace boost
{
namespace system
{
class system_error : public std::runtime_error
{
public:
system_error( error_code ec );
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system_error( error_code ec, const char * what_arg );
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system_error( error_code ec, const std::string & what_arg );
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system_error( int ev, const error_category & ecat,
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const char * what_arg );
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system_error( int ev, const error_category & ecat,
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const std::string & what_arg );
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system_error( int ev, const error_category & ecat);
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const error_code & code() const throw();
const char * what() const throw();
};
}
}</ pre >
</ blockquote >
< pre > system_error( error_code ec );</ pre >
< blockquote >
< p >< i > Effects:</ i > Constructs an object of class < code > system_error</ code > .</ p >
< p >< i > Postcondition:</ i > < code > code() == ec < br >
&& std::strcmp( this-> runtime_error::what(), "" ) == 0</ code ></ p >
</ blockquote >
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< pre > system_error( error_code ec, const char * what_arg );</ pre >
< blockquote >
< p >< i > Effects:</ i > Constructs an object of class < code > system_error</ code > .</ p >
< p >< i > Postcondition:</ i > < code > code() == ec < br >
&& std::strcmp( this-> runtime_error::what(), what_arg ) == 0</ code ></ p >
</ blockquote >
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< pre > system_error( error_code ec, const std::string & what_arg );</ pre >
< blockquote >
< p >< i > Effects:</ i > Constructs an object of class < code > system_error</ code > .</ p >
< p >< i > Postcondition:</ i > < code > code() == ec < br >
&& std::strcmp( this-> runtime_error::what(), what_arg.c_str() ) == 0</ code ></ p >
</ blockquote >
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< pre > system_error( int ev, const error_category & ecat,
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const char * what_arg );</ pre >
< blockquote >
< p >< i > Effects:</ i > Constructs an object of class < code > system_error</ code > .</ p >
< p >< i > Postcondition:</ i > < code > code() == error_code( ev, ecat )< br >
&& std::strcmp( this-> runtime_error::what(), what_arg ) == 0</ code ></ p >
</ blockquote >
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< pre > system_error( int ev, const error_category & ecat,
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const std::string & what_arg );</ pre >
< blockquote >
< p >< i > Effects:</ i > Constructs an object of class < code > system_error</ code > .</ p >
< p >< i > Postcondition:</ i > < code > code() == error_code( ev, ecat )< br >
&& std::strcmp( this-> runtime_error::what(), what_arg.c_str() ) == 0</ code ></ p >
</ blockquote >
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< pre > system_error( int ev, const error_category & ecat );</ pre >
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< blockquote >
< p >< i > Effects:</ i > Constructs an object of class < code > system_error</ code > .</ p >
< p >< i > Postcondition:</ i > < code > code() == error_code( ev, ecat )< br >
&& std::strcmp( this-> runtime_error::what(), "" ) == 0</ code ></ p >
</ blockquote >
< pre > const error_code & code() const;</ pre >
< blockquote >
< p >< i > Returns:</ i > < code > ec</ code > or < code > error_code( ev, ecat )</ code > , from
the constructor, as appropriate.</ p >
</ blockquote >
< pre > const char * what() const;</ pre >
< blockquote >
< p >< i > Returns: </ i > A string incorporating < code >
this-> runtime_error::what()</ code > and < code >
code.message()</ code > .</ p >
</ blockquote >
< hr >
< p > Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%B %d, %Y" startspan --> June 29, 2010<!--webbot bot="Timestamp" endspan i-checksum="14432" --> </ font >
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</ p >
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< p > © Copyright Beman Dawes, 2006, 2007, 2008</ p >
< p > Distributed under the Boost Software License, Version 1.0. See
< a href = "http://www.boost.org/LICENSE_1_0.txt" > www.boost.org/LICENSE_1_0.txt</ a ></ p >
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</ body >
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</ html >
