-@c Copyright (C) 1988,1989,1992,1993,1994,1996,1998,1999,2000,2001,2002 Free Software Foundation, Inc.
+@c Copyright (C) 1988,1989,1992,1993,1994,1996,1998,1999,2000,2001,2002, 2003
+@c Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.
* Labels as Values:: Getting pointers to labels, and computed gotos.
* Nested Functions:: As in Algol and Pascal, lexical scoping of functions.
* Constructing Calls:: Dispatching a call to another function.
-* Naming Types:: Giving a name to the type of some expression.
* Typeof:: @code{typeof}: referring to the type of an expression.
* Lvalues:: Using @samp{?:}, @samp{,} and casts in lvalues.
* Conditionals:: Omitting the middle operand of a @samp{?:} expression.
* Hex Floats:: Hexadecimal floating-point constants.
* Zero Length:: Zero-length arrays.
* Variable Length:: Arrays whose length is computed at run time.
+* Empty Structures:: Structures with no members.
* Variadic Macros:: Macros with a variable number of arguments.
* Escaped Newlines:: Slightly looser rules for escaped newlines.
* Multi-line Strings:: String literals with embedded newlines.
@c the above section title wrapped and causes an underfull hbox.. i
@c changed it from "within" to "in". --mew 4feb93
-
A compound statement enclosed in parentheses may appear as an expression
in GNU C@. This allows you to use loops, switches, and local variables
within an expression.
the initial value of a static variable.
If you don't know the type of the operand, you can still do this, but you
-must use @code{typeof} (@pxref{Typeof}) or type naming (@pxref{Naming
-Types}).
+must use @code{typeof} (@pxref{Typeof}).
Statement expressions are not supported fully in G++, and their fate
there is unclear. (It is possible that they will become fully supported
returned by @code{__builtin_apply}.
@end deftypefn
-@node Naming Types
-@section Naming an Expression's Type
-@cindex naming types
-
-You can give a name to the type of an expression using a @code{typedef}
-declaration with an initializer. Here is how to define @var{name} as a
-type name for the type of @var{exp}:
-
-@example
-typedef @var{name} = @var{exp};
-@end example
-
-This is useful in conjunction with the statements-within-expressions
-feature. Here is how the two together can be used to define a safe
-``maximum'' macro that operates on any arithmetic type:
-
-@example
-#define max(a,b) \
- (@{typedef _ta = (a), _tb = (b); \
- _ta _a = (a); _tb _b = (b); \
- _a > _b ? _a : _b; @})
-@end example
-
-@cindex underscores in variables in macros
-@cindex @samp{_} in variables in macros
-@cindex local variables in macros
-@cindex variables, local, in macros
-@cindex macros, local variables in
-
-The reason for using names that start with underscores for the local
-variables is to avoid conflicts with variable names that occur within the
-expressions that are substituted for @code{a} and @code{b}. Eventually we
-hope to design a new form of declaration syntax that allows you to declare
-variables whose scopes start only after their initializers; this will be a
-more reliable way to prevent such conflicts.
-
@node Typeof
@section Referring to a Type with @code{typeof}
@findex typeof
used. For example, you can use it in a declaration, in a cast, or inside
of @code{sizeof} or @code{typeof}.
+@code{typeof} is often useful in conjunction with the
+statements-within-expressions feature. Here is how the two together can
+be used to define a safe ``maximum'' macro that operates on any
+arithmetic type and evaluates each of its arguments exactly once:
+
+@example
+#define max(a,b) \
+ (@{ typeof (a) _a = (a); \
+ typeof (b) _b = (b); \
+ _a > _b ? _a : _b; @})
+@end example
+
+@cindex underscores in variables in macros
+@cindex @samp{_} in variables in macros
+@cindex local variables in macros
+@cindex variables, local, in macros
+@cindex macros, local variables in
+
+The reason for using names that start with underscores for the local
+variables is to avoid conflicts with variable names that occur within the
+expressions that are substituted for @code{a} and @code{b}. Eventually we
+hope to design a new form of declaration syntax that allows you to declare
+variables whose scopes start only after their initializers; this will be a
+more reliable way to prevent such conflicts.
+
+@noindent
+Some more examples of the use of @code{typeof}:
+
@itemize @bullet
@item
This declares @code{y} with the type of what @code{x} points to.
pointers to @code{char}.
@end itemize
+@emph{Compatibility Note:} In addition to @code{typeof}, GCC 2 supported
+a more limited extension which permitted one to write
+
+@example
+typedef @var{T} = @var{expr};
+@end example
+
+@noindent
+with the effect of declaring @var{T} to have the type of the expression
+@var{expr}. This extension does not work with GCC 3 (versions between
+3.0 and 3.2 will crash; 3.2.1 and later give an error). Code which
+relies on it should be rewritten to use @code{typeof}:
+
+@example
+typedef typeof(@var{expr}) @var{T};
+@end example
+
+@noindent
+This will work with all versions of GCC@.
+
@node Lvalues
@section Generalized Lvalues
@cindex compound expressions as lvalues
@cindex lvalues, generalized
@cindex extensions, @code{?:}
@cindex @code{?:} extensions
+
Compound expressions, conditional expressions and casts are allowed as
lvalues provided their operands are lvalues. This means that you can take
their addresses or store values into them.
GCC can allocate complex automatic variables in a noncontiguous
fashion; it's even possible for the real part to be in a register while
-the imaginary part is on the stack (or vice-versa). None of the
-supported debugging info formats has a way to represent noncontiguous
-allocation like this, so GCC describes a noncontiguous complex
-variable as if it were two separate variables of noncomplex type.
+the imaginary part is on the stack (or vice-versa). Only the DWARF2
+debug info format can represent this, so use of DWARF2 is recommended.
+If you are using the stabs debug info format, GCC describes a noncontiguous
+complex variable as if it were two separate variables of noncomplex type.
If the variable's actual name is @code{foo}, the two fictitious
variables are named @code{foo$real} and @code{foo$imag}. You can
examine and set these two fictitious variables with your debugger.
-A future version of GDB will know how to recognize such pairs and treat
-them as a single variable with a complex type.
-
@node Hex Floats
@section Hex Floats
@cindex hex floats
struct foo d[1] = @{ @{ 1 @{ 2, 3, 4 @} @} @}; // @r{Invalid.}
@end example
+@node Empty Structures
+@section Structures With No Members
+@cindex empty structures
+@cindex zero-size structures
+
+GCC permits a C structure to have no members:
+
+@example
+struct empty @{
+@};
+@end example
+
+The structure will have size zero. In C++, empty structures are part
+of the language. G++ treats empty structures as if they had a single
+member of type @code{char}.
+
@node Variable Length
@section Arrays of Variable Length
@cindex variable-length arrays
@code{vprintf}), specify the third parameter as zero. In this case the
compiler only checks the format string for consistency. For
@code{strftime} formats, the third parameter is required to be zero.
+Since non-static C++ methods have an implicit @code{this} argument, the
+arguments of such methods should be counted from two, not one, when
+giving values for @var{string-index} and @var{first-to-check}.
In the example above, the format string (@code{my_format}) is the second
argument of the function @code{my_print}, and the arguments to check
without the attribute.
The parameter @var{string-index} specifies which argument is the format
-string argument (starting from 1).
+string argument (starting from one). Since non-static C++ methods have
+an implicit @code{this} argument, the arguments of such methods should
+be counted from two.
The @code{format-arg} attribute allows you to identify your own
functions which modify format strings, so that GCC can check the
@item visibility ("@var{visibility_type}")
@cindex @code{visibility} attribute
The @code{visibility} attribute on ELF targets causes the declaration
-to be emitted with hidden, protected or internal visibility.
+to be emitted with default, hidden, protected or internal visibility.
@smallexample
void __attribute__ ((visibility ("protected")))
int i __attribute__ ((visibility ("hidden")));
@end smallexample
-See the ELF gABI for complete details, but the short story is
+See the ELF gABI for complete details, but the short story is:
@table @dfn
+@item default
+Default visibility is the normal case for ELF. This value is
+available for the visibility attribute to override other options
+that may change the assumed visibility of symbols.
+
@item hidden
Hidden visibility indicates that the symbol will not be placed into
the dynamic symbol table, so no other @dfn{module} (executable or
Not all ELF targets support this attribute.
@item regparm (@var{number})
+@cindex @code{regparm} attribute
@cindex functions that are passed arguments in registers on the 386
On the Intel 386, the @code{regparm} attribute causes the compiler to
pass up to @var{number} integer arguments in registers EAX,
variable number of arguments will continue to be passed all of their
arguments on the stack.
+Beware that on some ELF systems this attribute is unsuitable for
+global functions in shared libraries with lazy binding (which is the
+default). Lazy binding will send the first call via resolving code in
+the loader, which might assume EAX, EDX and ECX can be clobbered, as
+per the standard calling conventions. Solaris 8 is affected by this.
+GNU systems with GLIBC 2.1 or higher, and FreeBSD, are believed to be
+safe since the loaders there save all registers. (Lazy binding can be
+disabled with the linker or the loader if desired, to avoid the
+problem.)
+
@item stdcall
@cindex functions that pop the argument stack on the 386
On the Intel 386, the @code{stdcall} attribute causes the compiler to
assume that the called function will pop off the stack space used to
pass arguments, unless it takes a variable number of arguments.
-The PowerPC compiler for Windows NT currently ignores the @code{stdcall}
-attribute.
+@item fastcall
+@cindex functions that pop the argument stack on the 386
+On the Intel 386, the @code{fastcall} attribute causes the compiler to
+pass the first two arguments in the registers ECX and EDX. Subsequent
+arguments are passed on the stack. The called function will pop the
+arguments off the stack. If the number of arguments is variable all
+arguments are pushed on the stack.
@item cdecl
@cindex functions that do pop the argument stack on the 386
pass arguments. This is
useful to override the effects of the @option{-mrtd} switch.
-The PowerPC compiler for Windows NT currently ignores the @code{cdecl}
-attribute.
-
@item longcall/shortcall
@cindex functions called via pointer on the RS/6000 and PowerPC
On the RS/6000 and PowerPC, the @code{longcall} attribute causes the
the offset to the function from the call site into the @samp{BL}
instruction directly.
-@item dllimport
-@cindex functions which are imported from a dll on PowerPC Windows NT
-On the PowerPC running Windows NT, the @code{dllimport} attribute causes
-the compiler to call the function via a global pointer to the function
-pointer that is set up by the Windows NT dll library. The pointer name
-is formed by combining @code{__imp_} and the function name.
-
-@item dllexport
-@cindex functions which are exported from a dll on PowerPC Windows NT
-On the PowerPC running Windows NT, the @code{dllexport} attribute causes
-the compiler to provide a global pointer to the function pointer, so
-that it can be called with the @code{dllimport} attribute. The pointer
-name is formed by combining @code{__imp_} and the function name.
-
-@item exception (@var{except-func} [, @var{except-arg}])
-@cindex functions which specify exception handling on PowerPC Windows NT
-On the PowerPC running Windows NT, the @code{exception} attribute causes
-the compiler to modify the structured exception table entry it emits for
-the declared function. The string or identifier @var{except-func} is
-placed in the third entry of the structured exception table. It
-represents a function, which is called by the exception handling
-mechanism if an exception occurs. If it was specified, the string or
-identifier @var{except-arg} is placed in the fourth entry of the
-structured exception table.
-
@item function_vector
@cindex calling functions through the function vector on the H8/300 processors
Use this attribute on the H8/300 and H8/300H to indicate that the specified
@item interrupt
@cindex interrupt handler functions
-Use this attribute on the ARM, AVR, M32R/D and Xstormy16 ports to indicate
+Use this attribute on the ARM, AVR, C4x, M32R/D and Xstormy16 ports to indicate
that the specified function is an interrupt handler. The compiler will
generate function entry and exit sequences suitable for use in an
interrupt handler when this attribute is present.
@item naked
@cindex function without a prologue/epilogue code
-Use this attribute on the ARM, AVR and IP2K ports to indicate that the
+Use this attribute on the ARM, AVR, C4x and IP2K ports to indicate that the
specified function do not need prologue/epilogue sequences generated by
the compiler. It is up to the programmer to provide these sequences.
and may not be reachable with the @code{bl} instruction (the compiler will
generate the much slower @code{seth/add3/jl} instruction sequence).
+@item far
+@cindex functions which handle memory bank switching
+On 68HC11 and 68HC12 the @code{far} attribute causes the compiler to
+use a calling convention that takes care of switching memory banks when
+entering and leaving a function. This calling convention is also the
+default when using the @option{-mlong-calls} option.
+
+On 68HC12 the compiler will use the @code{call} and @code{rtc} instructions
+to call and return from a function.
+
+On 68HC11 the compiler will generate a sequence of instructions
+to invoke a board-specific routine to switch the memory bank and call the
+real function. The board-specific routine simulates a @code{call}.
+At the end of a function, it will jump to a board-specific routine
+instead of using @code{rts}. The board-specific return routine simulates
+the @code{rtc}.
+
+@item near
+@cindex functions which do not handle memory bank switching on 68HC11/68HC12
+On 68HC11 and 68HC12 the @code{near} attribute causes the compiler to
+use the normal calling convention based on @code{jsr} and @code{rts}.
+This attribute can be used to cancel the effect of the @option{-mlong-calls}
+option.
+
@end table
You can specify multiple attributes in a declaration by separating them
The keyword @code{__attribute__} allows you to specify special
attributes of variables or structure fields. This keyword is followed
-by an attribute specification inside double parentheses. Ten
-attributes are currently defined for variables: @code{aligned},
-@code{mode}, @code{nocommon}, @code{packed}, @code{section},
-@code{transparent_union}, @code{unused}, @code{deprecated},
-@code{vector_size}, and @code{weak}. Some other attributes are defined
-for variables on particular target systems. Other attributes are
-available for functions (@pxref{Function Attributes}) and for types
-(@pxref{Type Attributes}). Other front ends might define more
-attributes (@pxref{C++ Extensions,,Extensions to the C++ Language}).
+by an attribute specification inside double parentheses. Some
+attributes are currently defined generically for variables.
+Other attributes are defined for variables on particular target
+systems. Other attributes are available for functions
+(@pxref{Function Attributes}) and for types (@pxref{Type Attributes}).
+Other front ends might define more attributes
+(@pxref{C++ Extensions,,Extensions to the C++ Language}).
You may also specify attributes with @samp{__} preceding and following
each keyword. This allows you to use them in header files without
in an @code{__attribute__} will still only provide you with 8 byte
alignment. See your linker documentation for further information.
+@item cleanup (@var{cleanup_function})
+@cindex @code{cleanup} attribute
+The @code{cleanup} attribute runs a function when the variable goes
+out of scope. This attribute can only be applied to auto function
+scope variables; it may not be applied to parameters or variables
+with static storage duration. The function must take one parameter,
+a pointer to a type compatible with the variable. The return value
+of the function (if any) is ignored.
+
+If @option{-fexceptions} is enabled, then @var{cleanup_function}
+will be run during the stack unwinding that happens during the
+processing of the exception. Note that the @code{cleanup} attribute
+does not allow the exception to be caught, only to perform an action.
+It is undefined what happens if @var{cleanup_function} does not
+return normally.
+
+@item common
+@itemx nocommon
+@cindex @code{common} attribute
+@cindex @code{nocommon} attribute
+@opindex fcommon
+@opindex fno-common
+The @code{common} attribute requests GCC to place a variable in
+``common'' storage. The @code{nocommon} attribute requests the
+opposite -- to allocate space for it directly.
+
+These attributes override the default chosen by the
+@option{-fno-common} and @option{-fcommon} flags respectively.
+
+@item deprecated
+@cindex @code{deprecated} attribute
+The @code{deprecated} attribute results in a warning if the variable
+is used anywhere in the source file. This is useful when identifying
+variables that are expected to be removed in a future version of a
+program. The warning also includes the location of the declaration
+of the deprecated variable, to enable users to easily find further
+information about why the variable is deprecated, or what they should
+do instead. Note that the warnings only occurs for uses:
+
+@smallexample
+extern int old_var __attribute__ ((deprecated));
+extern int old_var;
+int new_fn () @{ return old_var; @}
+@end smallexample
+
+results in a warning on line 3 but not line 2.
+
+The @code{deprecated} attribute can also be used for functions and
+types (@pxref{Function Attributes}, @pxref{Type Attributes}.)
+
@item mode (@var{mode})
@cindex @code{mode} attribute
This attribute specifies the data type for the declaration---whichever
@samp{__word__} for the mode of a one-word integer, and @samp{pointer}
or @samp{__pointer__} for the mode used to represent pointers.
-@item nocommon
-@cindex @code{nocommon} attribute
-@opindex fno-common
-This attribute specifies requests GCC not to place a variable
-``common'' but instead to allocate space for it directly. If you
-specify the @option{-fno-common} flag, GCC will do this for all
-variables.
-
-Specifying the @code{nocommon} attribute for a variable provides an
-initialization of zeros. A variable may only be initialized in one
-source file.
-
@item packed
@cindex @code{packed} attribute
The @code{packed} attribute specifies that a variable or structure field
The @code{shared} attribute is only available on Windows NT@.
+@item tls_model ("@var{tls_model}")
+@cindex @code{tls_model} attribute
+The @code{tls_model} attribute sets thread-local storage model
+(@pxref{Thread-Local}) of a particular @code{__thread} variable,
+overriding @code{-ftls-model=} command line switch on a per-variable
+basis.
+The @var{tls_model} argument should be one of @code{global-dynamic},
+@code{local-dynamic}, @code{initial-exec} or @code{local-exec}.
+
+Not all targets support this attribute.
+
@item transparent_union
This attribute, attached to a function parameter which is a union, means
that the corresponding argument may have the type of any union member,
to be possibly unused. GCC will not produce a warning for this
variable.
-@item deprecated
-The @code{deprecated} attribute results in a warning if the variable
-is used anywhere in the source file. This is useful when identifying
-variables that are expected to be removed in a future version of a
-program. The warning also includes the location of the declaration
-of the deprecated variable, to enable users to easily find further
-information about why the variable is deprecated, or what they should
-do instead. Note that the warnings only occurs for uses:
-
-@smallexample
-extern int old_var __attribute__ ((deprecated));
-extern int old_var;
-int new_fn () @{ return old_var; @}
-@end smallexample
-
-results in a warning on line 3 but not line 2.
-
-The @code{deprecated} attribute can also be used for functions and
-types (@pxref{Function Attributes}, @pxref{Type Attributes}.)
-
@item vector_size (@var{bytes})
This attribute specifies the vector size for the variable, measured in
bytes. For example, the declaration:
@item weak
The @code{weak} attribute is described in @xref{Function Attributes}.
+@end table
+@subsection M32R/D Variable Attributes
+
+One attribute is currently defined for the M32R/D.
+
+@table @code
@item model (@var{model-name})
@cindex variable addressability on the M32R/D
Use this attribute on the M32R/D to set the addressability of an object.
Medium and large model objects may live anywhere in the 32-bit address space
(the compiler will generate @code{seth/add3} instructions to load their
addresses).
-
@end table
-To specify multiple attributes, separate them by commas within the
-double parentheses: for example, @samp{__attribute__ ((aligned (16),
-packed))}.
+@subsection i386 Variable Attributes
+
+Two attributes are currently defined for i386 configurations:
+@code{ms_struct} and @code{gcc_struct}
+
+@table @code
+@item ms_struct
+@itemx gcc_struct
+@cindex @code{ms_struct} attribute
+@cindex @code{gcc_struct} attribute
+
+If @code{packed} is used on a structure, or if bit-fields are used
+it may be that the Microsoft ABI packs them differently
+than GCC would normally pack them. Particularly when moving packed
+data between functions compiled with GCC and the native Microsoft compiler
+(either via function call or as data in a file), it may be necessary to access
+either format.
+
+Currently @option{-m[no-]ms-bitfields} is provided for the Windows X86
+compilers to match the native Microsoft compiler.
+@end table
@node Type Attributes
@section Specifying Attributes of Types
@noindent
force the compiler to insure (as far as it can) that each variable whose
type is @code{struct S} or @code{more_aligned_int} will be allocated and
-aligned @emph{at least} on a 8-byte boundary. On a Sparc, having all
+aligned @emph{at least} on a 8-byte boundary. On a SPARC, having all
variables of type @code{struct S} aligned to 8-byte boundaries allows
the compiler to use the @code{ldd} and @code{std} (doubleword load and
store) instructions when copying one variable of type @code{struct S} to
declaration, the above program would abort when compiled with
@option{-fstrict-aliasing}, which is on by default at @option{-O2} or
above in recent GCC versions.
+
+@subsection i386 Type Attributes
+
+Two attributes are currently defined for i386 configurations:
+@code{ms_struct} and @code{gcc_struct}
+
+@item ms_struct
+@itemx gcc_struct
+@cindex @code{ms_struct}
+@cindex @code{gcc_struct}
+
+If @code{packed} is used on a structure, or if bit-fields are used
+it may be that the Microsoft ABI packs them differently
+than GCC would normally pack them. Particularly when moving packed
+data between functions compiled with GCC and the native Microsoft compiler
+(either via function call or as data in a file), it may be necessary to access
+either format.
+
+Currently @option{-m[no-]ms-bitfields} is provided for the Windows X86
+compilers to match the native Microsoft compiler.
@end table
To specify multiple attributes, separate them by commas within the
You may not write a clobber description in a way that overlaps with an
input or output operand. For example, you may not have an operand
describing a register class with one member if you mention that register
-in the clobber list. There is no way for you to specify that an input
+in the clobber list. Variables declared to live in specific registers
+(@pxref{Explicit Reg Vars}), and used as asm input or output operands must
+have no part mentioned in the clobber description.
+There is no way for you to specify that an input
operand is modified without also specifying it as an output
operand. Note that if all the output operands you specify are for this
purpose (and hence unused), you will then also need to specify
Global register variables may not have initial values, because an
executable file has no means to supply initial contents for a register.
-On the Sparc, there are reports that g3 @dots{} g7 are suitable
+On the SPARC, there are reports that g3 @dots{} g7 are suitable
registers, but certain library functions, such as @code{getwd}, as well
as the subroutines for division and remainder, modify g3 and g4. g1 and
g2 are local temporaries.
class a @{
public:
- sub (int i)
+ void sub (int i)
@{
printf ("__FUNCTION__ = %s\n", __FUNCTION__);
printf ("__PRETTY_FUNCTION__ = %s\n", __PRETTY_FUNCTION__);
A floating point value, as wide as a DI mode integer, usually 64 bits.
@end table
-There are no @code{V1xx} vector modes - they would be identical to the
-corresponding base mode.
-
Specifying a combination that is not valid for the current architecture
will cause gcc to synthesize the instructions using a narrower mode.
For example, if you specify a variable of type @code{V4SI} and your
to and from other datatypes of the same size).
You cannot operate between vectors of different lengths or different
-signness without a cast.
+signedness without a cast.
A port that supports hardware vector operations, usually provides a set
of built-in functions that can be used to operate on vectors. For
@findex abort
@findex abs
@findex alloca
+@findex atan
+@findex atan2
+@findex atan2f
+@findex atan2l
+@findex atanf
+@findex atanl
@findex bcmp
@findex bzero
+@findex cabs
+@findex cabsf
+@findex cabsl
+@findex calloc
+@findex ceil
+@findex ceilf
+@findex ceill
@findex cimag
@findex cimagf
@findex cimagl
@findex fabsf
@findex fabsl
@findex ffs
+@findex floor
+@findex floorf
+@findex floorl
+@findex fmod
+@findex fmodf
+@findex fmodl
@findex fprintf
@findex fprintf_unlocked
@findex fputs
@findex log
@findex logf
@findex logl
+@findex malloc
@findex memcmp
@findex memcpy
+@findex mempcpy
@findex memset
+@findex nearbyint
+@findex nearbyintf
+@findex nearbyintl
+@findex pow
+@findex powf
+@findex powl
@findex printf
@findex printf_unlocked
+@findex putchar
+@findex puts
@findex rindex
+@findex round
+@findex roundf
+@findex roundl
+@findex scanf
@findex sin
@findex sinf
@findex sinl
+@findex snprintf
+@findex sprintf
@findex sqrt
@findex sqrtf
@findex sqrtl
+@findex sscanf
+@findex stpcpy
@findex strcat
@findex strchr
@findex strcmp
@findex strcpy
@findex strcspn
+@findex strdup
@findex strlen
@findex strncat
@findex strncmp
@findex strrchr
@findex strspn
@findex strstr
+@findex tan
+@findex tanf
+@findex tanl
+@findex trunc
+@findex truncf
+@findex truncl
+@findex vprintf
+@findex vscanf
+@findex vsnprintf
+@findex vsprintf
+@findex vsscanf
GCC provides a large number of built-in functions other than the ones
mentioned above. Some of these are for internal use in the processing
@opindex ansi
@opindex std
-The functions @code{abort}, @code{exit}, @code{_Exit} and @code{_exit}
-are recognized and presumed not to return, but otherwise are not built
-in. @code{_exit} is not recognized in strict ISO C mode (@option{-ansi},
-@option{-std=c89} or @option{-std=c99}). @code{_Exit} is not recognized in
-strict C89 mode (@option{-ansi} or @option{-std=c89}). All these functions
-have corresponding versions prefixed with @code{__builtin_}, which may be
-used even in strict C89 mode.
-
-Outside strict ISO C mode, the functions @code{alloca}, @code{bcmp},
-@code{bzero}, @code{index}, @code{rindex}, @code{ffs}, @code{fputs_unlocked},
-@code{printf_unlocked} and @code{fprintf_unlocked} may be handled as
-built-in functions. All these functions have corresponding versions
+Outside strict ISO C mode (@option{-ansi}, @option{-std=c89} or
+@option{-std=c99}), the functions @code{alloca}, @code{bcmp},
+@code{bzero}, @code{_exit}, @code{ffs}, @code{fprintf_unlocked},
+@code{fputs_unlocked}, @code{index}, @code{mempcpy}, @code{printf_unlocked},
+@code{rindex}, @code{stpcpy} and @code{strdup}
+may be handled as built-in functions.
+All these functions have corresponding versions
prefixed with @code{__builtin_}, which may be used even in strict C89
mode.
-The ISO C99 functions @code{conj}, @code{conjf}, @code{conjl},
-@code{creal}, @code{crealf}, @code{creall}, @code{cimag}, @code{cimagf},
-@code{cimagl}, @code{llabs} and @code{imaxabs} are handled as built-in
-functions except in strict ISO C90 mode. There are also built-in
-versions of the ISO C99 functions @code{cosf}, @code{cosl},
-@code{expf}, @code{expl}, @code{fabsf}, @code{fabsl},
-@code{logf}, @code{logl}, @code{sinf}, @code{sinl}, @code{sqrtf}, and
-@code{sqrtl}, that are recognized in any mode since ISO C90 reserves
-these names for the purpose to which ISO C99 puts them. All these
-functions have corresponding versions prefixed with @code{__builtin_}.
-
-The ISO C90 functions @code{abs}, @code{cos}, @code{exp}, @code{fabs},
-@code{fprintf}, @code{fputs}, @code{labs}, @code{log},
-@code{memcmp}, @code{memcpy},
-@code{memset}, @code{printf}, @code{sin}, @code{sqrt}, @code{strcat},
-@code{strchr}, @code{strcmp}, @code{strcpy}, @code{strcspn},
-@code{strlen}, @code{strncat}, @code{strncmp}, @code{strncpy},
-@code{strpbrk}, @code{strrchr}, @code{strspn}, and @code{strstr} are all
-recognized as built-in functions unless @option{-fno-builtin} is
-specified (or @option{-fno-builtin-@var{function}} is specified for an
-individual function). All of these functions have corresponding
-versions prefixed with @code{__builtin_}.
+The ISO C99 functions
+@code{cabs}, @code{cabsf}, @code{cabsl},
+@code{conj}, @code{conjf}, @code{conjl},
+@code{creal}, @code{crealf}, @code{creall},
+@code{cimag}, @code{cimagf}, @code{cimagl},
+@code{_Exit}, @code{imaxabs}, @code{llabs},
+@code{nearbyint}, @code{nearbyintf}, @code{nearbyintl},
+@code{round}, @code{roundf}, @code{roundl}, @code{snprintf},
+@code{trunc}, @code{truncf}, @code{truncl},
+@code{vscanf}, @code{vsnprintf} and @code{vsscanf}
+are handled as built-in functions
+except in strict ISO C90 mode (@option{-ansi} or @option{-std=c89}).
+
+There are also built-in versions of the ISO C99 functions @code{atan2f},
+@code{atan2l}, @code{atanf}, @code{atanl}, @code{ceilf}, @code{ceill},
+@code{cosf}, @code{cosl},
+@code{expf}, @code{expl}, @code{fabsf}, @code{fabsl}, @code{floorf},
+@code{floorl}, @code{fmodf}, @code{fmodl},
+@code{logf}, @code{logl}, @code{powf}, @code{powl},
+@code{sinf}, @code{sinl}, @code{sqrtf}, @code{sqrtl},
+@code{tanf} and @code{tanl}
+that are recognized in any mode since ISO C90 reserves these names for
+the purpose to which ISO C99 puts them. All these functions have
+corresponding versions prefixed with @code{__builtin_}.
+
+The ISO C90 functions @code{abort}, @code{abs}, @code{atan}, @code{atan2},
+@code{calloc}, @code{ceil}, @code{cos}, @code{exit},
+@code{exp}, @code{fabs}, @code{floor}, @code{fmod},
+@code{fprintf}, @code{fputs}, @code{labs}, @code{log}, @code{malloc},
+@code{memcmp}, @code{memcpy}, @code{memset}, @code{pow}, @code{printf},
+@code{putchar}, @code{puts}, @code{scanf}, @code{sin}, @code{snprintf},
+@code{sprintf}, @code{sqrt}, @code{sscanf},
+@code{strcat}, @code{strchr}, @code{strcmp},
+@code{strcpy}, @code{strcspn}, @code{strlen}, @code{strncat}, @code{strncmp},
+@code{strncpy}, @code{strpbrk}, @code{strrchr}, @code{strspn}, @code{strstr},
+@code{tan}, @code{vprintf} and @code{vsprintf}
+are all recognized as built-in functions unless
+@option{-fno-builtin} is specified (or @option{-fno-builtin-@var{function}}
+is specified for an individual function). All of these functions have
+corresponding versions prefixed with @code{__builtin_}.
GCC provides built-in versions of the ISO C99 floating point comparison
macros that avoid raising exceptions for unordered operands. They have
Similar to @code{__builtin_huge_val}, except the return type is @code{float}.
@end deftypefn
-@deftypefn {Built-in Function} long double __builtin_huge_vall (void)
+@deftypefn {Built-in Function} {long double} __builtin_huge_vall (void)
Similar to @code{__builtin_huge_val}, except the return
type is @code{long double}.
@end deftypefn
Similar to @code{__builtin_inf}, except the return type is @code{float}.
@end deftypefn
-@deftypefn {Built-in Function} long double __builtin_infl (void)
+@deftypefn {Built-in Function} {long double} __builtin_infl (void)
Similar to @code{__builtin_inf}, except the return
type is @code{long double}.
@end deftypefn
+@deftypefn {Built-in Function} double __builtin_nan (const char *str)
+This is an implementation of the ISO C99 function @code{nan}.
+
+Since ISO C99 defines this function in terms of @code{strtod}, which we
+do not implement, a description of the parsing is in order. The string
+is parsed as by @code{strtol}; that is, the base is recognized by
+leading @samp{0} or @samp{0x} prefixes. The number parsed is placed
+in the significand such that the least significant bit of the number
+is at the least significant bit of the significand. The number is
+truncated to fit the significand field provided. The significand is
+forced to be a quiet NaN.
+
+This function, if given a string literal, is evaluated early enough
+that it is considered a compile-time constant.
+@end deftypefn
+
+@deftypefn {Built-in Function} float __builtin_nanf (const char *str)
+Similar to @code{__builtin_nan}, except the return type is @code{float}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {long double} __builtin_nanl (const char *str)
+Similar to @code{__builtin_nan}, except the return type is @code{long double}.
+@end deftypefn
+
+@deftypefn {Built-in Function} double __builtin_nans (const char *str)
+Similar to @code{__builtin_nan}, except the significand is forced
+to be a signaling NaN. The @code{nans} function is proposed by
+@uref{http://std.dkuug.dk/JTC1/SC22/WG14/www/docs/n965.htm,,WG14 N965}.
+@end deftypefn
+
+@deftypefn {Built-in Function} float __builtin_nansf (const char *str)
+Similar to @code{__builtin_nans}, except the return type is @code{float}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {long double} __builtin_nansl (const char *str)
+Similar to @code{__builtin_nans}, except the return type is @code{long double}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ffs (unsigned int x)
+Returns one plus the index of the least significant 1-bit of @var{x}, or
+if @var{x} is zero, returns zero.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_clz (unsigned int x)
+Returns the number of leading 0-bits in @var{x}, starting at the most
+significant bit position. If @var{x} is 0, the result is undefined.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ctz (unsigned int x)
+Returns the number of trailing 0-bits in @var{x}, starting at the least
+significant bit position. If @var{x} is 0, the result is undefined.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_popcount (unsigned int x)
+Returns the number of 1-bits in @var{x}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_parity (unsigned int x)
+Returns the parity of @var{x}, i.@:e. the number of 1-bits in @var{x}
+modulo 2.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ffsl (unsigned long)
+Similar to @code{__builtin_ffs}, except the argument type is
+@code{unsigned long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_clzl (unsigned long)
+Similar to @code{__builtin_clz}, except the argument type is
+@code{unsigned long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ctzl (unsigned long)
+Similar to @code{__builtin_ctz}, except the argument type is
+@code{unsigned long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_popcountl (unsigned long)
+Similar to @code{__builtin_popcount}, except the argument type is
+@code{unsigned long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_parityl (unsigned long)
+Similar to @code{__builtin_parity}, except the argument type is
+@code{unsigned long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ffsll (unsigned long long)
+Similar to @code{__builtin_ffs}, except the argument type is
+@code{unsigned long long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_clzll (unsigned long long)
+Similar to @code{__builtin_clz}, except the argument type is
+@code{unsigned long long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ctzll (unsigned long long)
+Similar to @code{__builtin_ctz}, except the argument type is
+@code{unsigned long long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_popcountll (unsigned long long)
+Similar to @code{__builtin_popcount}, except the argument type is
+@code{unsigned long long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_parityll (unsigned long long)
+Similar to @code{__builtin_parity}, except the argument type is
+@code{unsigned long long}.
+@end deftypefn
+
+
@node Target Builtins
@section Built-in Functions Specific to Particular Target Machines
@menu
* Alpha Built-in Functions::
+* ARM Built-in Functions::
* X86 Built-in Functions::
* PowerPC AltiVec Built-in Functions::
@end menu
void __builtin_set_thread_pointer (void *)
@end example
+@node ARM Built-in Functions
+@subsection ARM Built-in Functions
+
+These built-in functions are available for the ARM family of
+processors, when the @option{-mcpu=iwmmxt} switch is used:
+
+@example
+typedef int __v2si __attribute__ ((__mode__ (__V2SI__)))
+
+v2si __builtin_arm_waddw (v2si, v2si)
+v2si __builtin_arm_waddw (v2si, v2si)
+v2si __builtin_arm_wsubw (v2si, v2si)
+v2si __builtin_arm_wsubw (v2si, v2si)
+v2si __builtin_arm_waddwss (v2si, v2si)
+v2si __builtin_arm_wsubwss (v2si, v2si)
+v2si __builtin_arm_wsubwss (v2si, v2si)
+v2si __builtin_arm_wsubwss (v2si, v2si)
+v2si __builtin_arm_wsubwss (v2si, v2si)
+v2si __builtin_arm_waddwus (v2si, v2si)
+v2si __builtin_arm_wsubwus (v2si, v2si)
+v2si __builtin_arm_wsubwus (v2si, v2si)
+v2si __builtin_arm_wmaxuw (v2si, v2si)
+v2si __builtin_arm_wmaxsw (v2si, v2si)
+v2si __builtin_arm_wavg2br (v2si, v2si)
+v2si __builtin_arm_wavg2hr (v2si, v2si)
+v2si __builtin_arm_wavg2b (v2si, v2si)
+v2si __builtin_arm_wavg2h (v2si, v2si)
+v2si __builtin_arm_waccb (v2si)
+v2si __builtin_arm_wacch (v2si)
+v2si __builtin_arm_waccw (v2si)
+v2si __builtin_arm_wmacs (v2si, v2si, v2si)
+v2si __builtin_arm_wmacsz (v2si, v2si, v2si)
+v2si __builtin_arm_wmacu (v2si, v2si, v2si)
+v2si __builtin_arm_wmacuz (v2si, v2si)
+v2si __builtin_arm_wsadb (v2si, v2si)
+v2si __builtin_arm_wsadbz (v2si, v2si)
+v2si __builtin_arm_wsadh (v2si, v2si)
+v2si __builtin_arm_wsadhz (v2si, v2si)
+v2si __builtin_arm_walign (v2si, v2si)
+v2si __builtin_arm_tmia (v2si, int, int)
+v2si __builtin_arm_tmiaph (v2si, int, int)
+v2si __builtin_arm_tmiabb (v2si, int, int)
+v2si __builtin_arm_tmiabt (v2si, int, int)
+v2si __builtin_arm_tmiatb (v2si, int, int)
+v2si __builtin_arm_tmiatt (v2si, int, int)
+int __builtin_arm_tmovmskb (v2si)
+int __builtin_arm_tmovmskh (v2si)
+int __builtin_arm_tmovmskw (v2si)
+v2si __builtin_arm_wmadds (v2si, v2si)
+v2si __builtin_arm_wmaddu (v2si, v2si)
+v2si __builtin_arm_wpackhss (v2si, v2si)
+v2si __builtin_arm_wpackwss (v2si, v2si)
+v2si __builtin_arm_wpackdss (v2si, v2si)
+v2si __builtin_arm_wpackhus (v2si, v2si)
+v2si __builtin_arm_wpackwus (v2si, v2si)
+v2si __builtin_arm_wpackdus (v2si, v2si)
+v2si __builtin_arm_waddb (v2si, v2si)
+v2si __builtin_arm_waddh (v2si, v2si)
+v2si __builtin_arm_waddw (v2si, v2si)
+v2si __builtin_arm_waddbss (v2si, v2si)
+v2si __builtin_arm_waddhss (v2si, v2si)
+v2si __builtin_arm_waddwss (v2si, v2si)
+v2si __builtin_arm_waddbus (v2si, v2si)
+v2si __builtin_arm_waddhus (v2si, v2si)
+v2si __builtin_arm_waddwus (v2si, v2si)
+v2si __builtin_arm_wsubb (v2si, v2si)
+v2si __builtin_arm_wsubh (v2si, v2si)
+v2si __builtin_arm_wsubw (v2si, v2si)
+v2si __builtin_arm_wsubbss (v2si, v2si)
+v2si __builtin_arm_wsubhss (v2si, v2si)
+v2si __builtin_arm_wsubwss (v2si, v2si)
+v2si __builtin_arm_wsubbus (v2si, v2si)
+v2si __builtin_arm_wsubhus (v2si, v2si)
+v2si __builtin_arm_wsubwus (v2si, v2si)
+v2si __builtin_arm_wand (v2si, v2si)
+v2si __builtin_arm_wandn (v2si, v2si)
+v2si __builtin_arm_wor (v2si, v2si)
+v2si __builtin_arm_wxor (v2si, v2si)
+v2si __builtin_arm_wcmpeqb (v2si, v2si)
+v2si __builtin_arm_wcmpeqh (v2si, v2si)
+v2si __builtin_arm_wcmpeqw (v2si, v2si)
+v2si __builtin_arm_wcmpgtub (v2si, v2si)
+v2si __builtin_arm_wcmpgtuh (v2si, v2si)
+v2si __builtin_arm_wcmpgtuw (v2si, v2si)
+v2si __builtin_arm_wcmpgtsb (v2si, v2si)
+v2si __builtin_arm_wcmpgtsh (v2si, v2si)
+v2si __builtin_arm_wcmpgtsw (v2si, v2si)
+int __builtin_arm_textrmsb (v2si, int)
+int __builtin_arm_textrmsh (v2si, int)
+int __builtin_arm_textrmsw (v2si, int)
+int __builtin_arm_textrmub (v2si, int)
+int __builtin_arm_textrmuh (v2si, int)
+int __builtin_arm_textrmuw (v2si, int)
+v2si __builtin_arm_tinsrb (v2si, int, int)
+v2si __builtin_arm_tinsrh (v2si, int, int)
+v2si __builtin_arm_tinsrw (v2si, int, int)
+v2si __builtin_arm_wmaxsw (v2si, v2si)
+v2si __builtin_arm_wmaxsh (v2si, v2si)
+v2si __builtin_arm_wmaxsb (v2si, v2si)
+v2si __builtin_arm_wmaxuw (v2si, v2si)
+v2si __builtin_arm_wmaxuh (v2si, v2si)
+v2si __builtin_arm_wmaxub (v2si, v2si)
+v2si __builtin_arm_wminsw (v2si, v2si)
+v2si __builtin_arm_wminsh (v2si, v2si)
+v2si __builtin_arm_wminsb (v2si, v2si)
+v2si __builtin_arm_wminuw (v2si, v2si)
+v2si __builtin_arm_wminuh (v2si, v2si)
+v2si __builtin_arm_wminub (v2si, v2si)
+v2si __builtin_arm_wmuluh (v2si, v2si)
+v2si __builtin_arm_wmulsh (v2si, v2si)
+v2si __builtin_arm_wmulul (v2si, v2si)
+v2si __builtin_arm_wshufh (v2si, int)
+v2si __builtin_arm_wsllh (v2si, v2si)
+v2si __builtin_arm_wsllw (v2si, v2si)
+v2si __builtin_arm_wslld (v2si, v2si)
+v2si __builtin_arm_wsrah (v2si, v2si)
+v2si __builtin_arm_wsraw (v2si, v2si)
+v2si __builtin_arm_wsrad (v2si, v2si)
+v2si __builtin_arm_wsrlh (v2si, v2si)
+v2si __builtin_arm_wsrlw (v2si, v2si)
+v2si __builtin_arm_wsrld (v2si, v2si)
+v2si __builtin_arm_wrorh (v2si, v2si)
+v2si __builtin_arm_wrorw (v2si, v2si)
+v2si __builtin_arm_wrord (v2si, v2si)
+v2si __builtin_arm_wsllhi (v2si, int)
+v2si __builtin_arm_wsllwi (v2si, int)
+v2si __builtin_arm_wslldi (v2si, v2si)
+v2si __builtin_arm_wsrahi (v2si, int)
+v2si __builtin_arm_wsrawi (v2si, int)
+v2si __builtin_arm_wsradi (v2si, v2si)
+v2si __builtin_arm_wsrlwi (v2si, int)
+v2si __builtin_arm_wsrldi (v2si, int)
+v2si __builtin_arm_wrorhi (v2si, int)
+v2si __builtin_arm_wrorwi (v2si, int)
+v2si __builtin_arm_wrordi (v2si, int)
+v2si __builtin_arm_wunpckihb (v2si, v2si)
+v2si __builtin_arm_wunpckihh (v2si, v2si)
+v2si __builtin_arm_wunpckihw (v2si, v2si)
+v2si __builtin_arm_wunpckilb (v2si, v2si)
+v2si __builtin_arm_wunpckilh (v2si, v2si)
+v2si __builtin_arm_wunpckilw (v2si, v2si)
+v2si __builtin_arm_wunpckehsb (v2si)
+v2si __builtin_arm_wunpckehsh (v2si)
+v2si __builtin_arm_wunpckehsw (v2si)
+v2si __builtin_arm_wunpckehub (v2si)
+v2si __builtin_arm_wunpckehuh (v2si)
+v2si __builtin_arm_wunpckehuw (v2si)
+v2si __builtin_arm_wunpckelsb (v2si)
+v2si __builtin_arm_wunpckelsh (v2si)
+v2si __builtin_arm_wunpckelsw (v2si)
+v2si __builtin_arm_wunpckelub (v2si)
+v2si __builtin_arm_wunpckeluh (v2si)
+v2si __builtin_arm_wunpckeluw (v2si)
+v2si __builtin_arm_wsubwss (v2si, v2si)
+v2si __builtin_arm_wsraw (v2si, v2si)
+v2si __builtin_arm_wsrad (v2si, v2si)
+@end example
+
@node X86 Built-in Functions
@subsection X86 Built-in Functions
v4si __builtin_ia32_cmpeqss (v4sf, v4sf)
v4si __builtin_ia32_cmpltss (v4sf, v4sf)
v4si __builtin_ia32_cmpless (v4sf, v4sf)
-v4si __builtin_ia32_cmpgtss (v4sf, v4sf)
-v4si __builtin_ia32_cmpgess (v4sf, v4sf)
v4si __builtin_ia32_cmpunordss (v4sf, v4sf)
v4si __builtin_ia32_cmpneqss (v4sf, v4sf)
v4si __builtin_ia32_cmpnlts (v4sf, v4sf)
v4si __builtin_ia32_cmpnless (v4sf, v4sf)
-v4si __builtin_ia32_cmpngtss (v4sf, v4sf)
-v4si __builtin_ia32_cmpngess (v4sf, v4sf)
v4si __builtin_ia32_cmpordss (v4sf, v4sf)
v4sf __builtin_ia32_maxps (v4sf, v4sf)
v4sf __builtin_ia32_maxss (v4sf, v4sf)
The following pragmas are available for all architectures running the
Darwin operating system. These are useful for compatibility with other
-MacOS compilers.
+Mac OS compilers.
@table @code
@item mark @var{tokens}@dots{}
This pragma is similar in intent to to the asm labels extension
(@pxref{Asm Labels}) in that the system programmer wants to change
the assembly-level ABI without changing the source-level API. The
-preprocessor defines @code{__EXTERN_PREFIX} if the pragma is available.
+preprocessor defines @code{__PRAGMA_EXTERN_PREFIX} if the pragma is
+available.
@end table
@node Unnamed Fields
that document the exact semantics of the language extension.
@itemize @bullet
+@item
@b{[intro.execution]}
New text after paragraph 4
@quotation
The storage for an object of thread storage duration shall be
-staticly initialized before the first statement of the thread startup
+statically initialized before the first statement of the thread startup
function. An object of thread storage duration shall not require
dynamic initialization.
@end quotation
However, side effects in @code{X} or @code{Y} may cause unintended
behavior. For example, @code{MIN (i++, j++)} will fail, incrementing
-the smaller counter twice. A GNU C extension allows you to write safe
-macros that avoid this kind of problem (@pxref{Naming Types,,Naming an
-Expression's Type}). However, writing @code{MIN} and @code{MAX} as
-macros also forces you to use function-call notation for a
-fundamental arithmetic operation. Using GNU C++ extensions, you can
-write @w{@samp{int min = i <? j;}} instead.
+the smaller counter twice. The GNU C @code{typeof} extension allows you
+to write safe macros that avoid this kind of problem (@pxref{Typeof}).
+However, writing @code{MIN} and @code{MAX} as macros also forces you to
+use function-call notation for a fundamental arithmetic operation.
+Using GNU C++ extensions, you can write @w{@samp{int min = i <? j;}}
+instead.
Since @code{<?} and @code{>?} are built into the compiler, they properly
handle expressions with side-effects; @w{@samp{int min = i++ <? j++;}}
@node Template Instantiation
@section Where's the Template?
-
@cindex template instantiation
C++ templates are the first language feature to require more
instances required by your explicit instantiations (but not by any
other files) without having to specify them as well.
-g++ has extended the template instantiation syntax outlined in the
-Working Paper to allow forward declaration of explicit instantiations
+g++ has extended the template instantiation syntax given in the ISO
+standard to allow forward declaration of explicit instantiations
(with @code{extern}), instantiation of the compiler support data for a
template class (i.e.@: the vtable) without instantiating any of its
members (with @code{inline}), and instantiation of only the static data
@node Bound member functions
@section Extracting the function pointer from a bound pointer to member function
-
@cindex pmf
@cindex pointer to member function
@cindex bound pointer to member function
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