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These macros define the sizes and other characteristics of the standard basic data types used in programs being compiled. Unlike the macros in the previous section, these apply to specific features of C and related languages, rather than to fundamental aspects of storage layout.
A C expression for the size in bits of the type
int
on the target machine. If you don't define this, the default is one word.
A C expression for the size in bits of the type
short
on the target machine. If you don't define this, the default is half a word. (If this would be less than one storage unit, it is rounded up to one unit.)
A C expression for the size in bits of the type
long
on the target machine. If you don't define this, the default is one word.
On some machines, the size used for the Ada equivalent of the type
long
by a native Ada compiler differs from that used by C. In that situation, define this macro to be a C expression to be used for the size of that type. If you don't define this, the default is the value ofLONG_TYPE_SIZE
.
A C expression for the size in bits of the type
long long
on the target machine. If you don't define this, the default is two words. If you want to support GNU Ada on your machine, the value of this macro must be at least 64.
A C expression for the size in bits of the type
char
on the target machine. If you don't define this, the default isBITS_PER_UNIT
.
A C expression for the size in bits of the C++ type
bool
and C99 type_Bool
on the target machine. If you don't define this, and you probably shouldn't, the default isCHAR_TYPE_SIZE
.
A C expression for the size in bits of the type
float
on the target machine. If you don't define this, the default is one word.
A C expression for the size in bits of the type
double
on the target machine. If you don't define this, the default is two words.
A C expression for the size in bits of the type
long double
on the target machine. If you don't define this, the default is two words.
A C expression for the size in bits of the type
short _Fract
on the target machine. If you don't define this, the default isBITS_PER_UNIT
.
A C expression for the size in bits of the type
_Fract
on the target machine. If you don't define this, the default isBITS_PER_UNIT * 2
.
A C expression for the size in bits of the type
long _Fract
on the target machine. If you don't define this, the default isBITS_PER_UNIT * 4
.
A C expression for the size in bits of the type
long long _Fract
on the target machine. If you don't define this, the default isBITS_PER_UNIT * 8
.
A C expression for the size in bits of the type
short _Accum
on the target machine. If you don't define this, the default isBITS_PER_UNIT * 2
.
A C expression for the size in bits of the type
_Accum
on the target machine. If you don't define this, the default isBITS_PER_UNIT * 4
.
A C expression for the size in bits of the type
long _Accum
on the target machine. If you don't define this, the default isBITS_PER_UNIT * 8
.
A C expression for the size in bits of the type
long long _Accum
on the target machine. If you don't define this, the default isBITS_PER_UNIT * 16
.
Define this macro if
LONG_DOUBLE_TYPE_SIZE
is not constant or if you want routines in libgcc2.a for a size other thanLONG_DOUBLE_TYPE_SIZE
. If you don't define this, the default isLONG_DOUBLE_TYPE_SIZE
.
Define this macro if neither
LIBGCC2_DOUBLE_TYPE_SIZE
norLIBGCC2_LONG_DOUBLE_TYPE_SIZE
isDFmode
but you wantDFmode
routines in libgcc2.a anyway. If you don't define this and eitherLIBGCC2_DOUBLE_TYPE_SIZE
orLIBGCC2_LONG_DOUBLE_TYPE_SIZE
is 64 then the default is 1, otherwise it is 0.
Define this macro if
LIBGCC2_LONG_DOUBLE_TYPE_SIZE
is notXFmode
but you wantXFmode
routines in libgcc2.a anyway. If you don't define this andLIBGCC2_LONG_DOUBLE_TYPE_SIZE
is 80 then the default is 1, otherwise it is 0.
Define this macro if
LIBGCC2_LONG_DOUBLE_TYPE_SIZE
is notTFmode
but you wantTFmode
routines in libgcc2.a anyway. If you don't define this andLIBGCC2_LONG_DOUBLE_TYPE_SIZE
is 128 then the default is 1, otherwise it is 0.
Define these macros to be the size in bits of the mantissa of
SFmode
,DFmode
,XFmode
andTFmode
values, if the defaults in libgcc2.h are inappropriate. By default,FLT_MANT_DIG
is used forSF_SIZE
,LDBL_MANT_DIG
forXF_SIZE
andTF_SIZE
, andDBL_MANT_DIG
orLDBL_MANT_DIG
forDF_SIZE
according to whetherLIBGCC2_DOUBLE_TYPE_SIZE
orLIBGCC2_LONG_DOUBLE_TYPE_SIZE
is 64.
A C expression for the value for
FLT_EVAL_METHOD
in float.h, assuming, if applicable, that the floating-point control word is in its default state. If you do not define this macro the value ofFLT_EVAL_METHOD
will be zero.
A C expression for the size in bits of the widest floating-point format supported by the hardware. If you define this macro, you must specify a value less than or equal to the value of
LONG_DOUBLE_TYPE_SIZE
. If you do not define this macro, the value ofLONG_DOUBLE_TYPE_SIZE
is the default.
An expression whose value is 1 or 0, according to whether the type
char
should be signed or unsigned by default. The user can always override this default with the options -fsigned-char and -funsigned-char.
This target hook should return true if the compiler should give an
enum
type only as many bytes as it takes to represent the range of possible values of that type. It should return false if allenum
types should be allocated likeint
.The default is to return false.
A C expression for a string describing the name of the data type to use for size values. The typedef name
size_t
is defined using the contents of the string.The string can contain more than one keyword. If so, separate them with spaces, and write first any length keyword, then
unsigned
if appropriate, and finallyint
. The string must exactly match one of the data type names defined in the functioninit_decl_processing
in the file c-decl.c. You may not omitint
or change the order—that would cause the compiler to crash on startup.If you don't define this macro, the default is
"long unsigned int"
.
A C expression for a string describing the name of the data type to use for the result of subtracting two pointers. The typedef name
ptrdiff_t
is defined using the contents of the string. SeeSIZE_TYPE
above for more information.If you don't define this macro, the default is
"long int"
.
A C expression for a string describing the name of the data type to use for wide characters. The typedef name
wchar_t
is defined using the contents of the string. SeeSIZE_TYPE
above for more information.If you don't define this macro, the default is
"int"
.
A C expression for the size in bits of the data type for wide characters. This is used in
cpp
, which cannot make use ofWCHAR_TYPE
.
A C expression for a string describing the name of the data type to use for wide characters passed to
printf
and returned fromgetwc
. The typedef namewint_t
is defined using the contents of the string. SeeSIZE_TYPE
above for more information.If you don't define this macro, the default is
"unsigned int"
.
A C expression for a string describing the name of the data type that can represent any value of any standard or extended signed integer type. The typedef name
intmax_t
is defined using the contents of the string. SeeSIZE_TYPE
above for more information.If you don't define this macro, the default is the first of
"int"
,"long int"
, or"long long int"
that has as much precision aslong long int
.
A C expression for a string describing the name of the data type that can represent any value of any standard or extended unsigned integer type. The typedef name
uintmax_t
is defined using the contents of the string. SeeSIZE_TYPE
above for more information.If you don't define this macro, the default is the first of
"unsigned int"
,"long unsigned int"
, or"long long unsigned int"
that has as much precision aslong long unsigned int
.
C expressions for the standard types
sig_atomic_t
,int8_t
,int16_t
,int32_t
,int64_t
,uint8_t
,uint16_t
,uint32_t
,uint64_t
,int_least8_t
,int_least16_t
,int_least32_t
,int_least64_t
,uint_least8_t
,uint_least16_t
,uint_least32_t
,uint_least64_t
,int_fast8_t
,int_fast16_t
,int_fast32_t
,int_fast64_t
,uint_fast8_t
,uint_fast16_t
,uint_fast32_t
,uint_fast64_t
,intptr_t
, anduintptr_t
. SeeSIZE_TYPE
above for more information.If any of these macros evaluates to a null pointer, the corresponding type is not supported; if GCC is configured to provide
<stdint.h>
in such a case, the header provided may not conform to C99, depending on the type in question. The defaults for all of these macros are null pointers.
The C++ compiler represents a pointer-to-member-function with a struct that looks like:
struct { union { void (*fn)(); ptrdiff_t vtable_index; }; ptrdiff_t delta; };The C++ compiler must use one bit to indicate whether the function that will be called through a pointer-to-member-function is virtual. Normally, we assume that the low-order bit of a function pointer must always be zero. Then, by ensuring that the vtable_index is odd, we can distinguish which variant of the union is in use. But, on some platforms function pointers can be odd, and so this doesn't work. In that case, we use the low-order bit of the
delta
field, and shift the remainder of thedelta
field to the left.GCC will automatically make the right selection about where to store this bit using the
FUNCTION_BOUNDARY
setting for your platform. However, some platforms such as ARM/Thumb haveFUNCTION_BOUNDARY
set such that functions always start at even addresses, but the lowest bit of pointers to functions indicate whether the function at that address is in ARM or Thumb mode. If this is the case of your architecture, you should define this macro toptrmemfunc_vbit_in_delta
.In general, you should not have to define this macro. On architectures in which function addresses are always even, according to
FUNCTION_BOUNDARY
, GCC will automatically define this macro toptrmemfunc_vbit_in_pfn
.
Normally, the C++ compiler uses function pointers in vtables. This macro allows the target to change to use “function descriptors” instead. Function descriptors are found on targets for whom a function pointer is actually a small data structure. Normally the data structure consists of the actual code address plus a data pointer to which the function's data is relative.
If vtables are used, the value of this macro should be the number of words that the function descriptor occupies.