GNU Info
(gcc-300.info)Type Layout
Layout of Source Language Data Types
====================================
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.
`INT_TYPE_SIZE'
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.
`MAX_INT_TYPE_SIZE'
Maximum number for the size in bits of the type `int' on the target
machine. If this is undefined, the default is `INT_TYPE_SIZE'.
Otherwise, it is the constant value that is the largest value that
`INT_TYPE_SIZE' can have at run-time. This is used in `cpp'.
`SHORT_TYPE_SIZE'
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.)
`LONG_TYPE_SIZE'
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.
`MAX_LONG_TYPE_SIZE'
Maximum number for the size in bits of the type `long' on the
target machine. If this is undefined, the default is
`LONG_TYPE_SIZE'. Otherwise, it is the constant value that is the
largest value that `LONG_TYPE_SIZE' can have at run-time. This is
used in `cpp'.
`LONG_LONG_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.
`CHAR_TYPE_SIZE'
A C expression for the size in bits of the type `char' on the
target machine. If you don't define this, the default is
`BITS_PER_UNIT'.
`MAX_CHAR_TYPE_SIZE'
Maximum number for the size in bits of the type `char' on the
target machine. If this is undefined, the default is
`CHAR_TYPE_SIZE'. Otherwise, it is the constant value that is the
largest value that `CHAR_TYPE_SIZE' can have at run-time. This is
used in `cpp'.
`BOOL_TYPE_SIZE'
A C expression for the size in bits of the C++ type `bool' on the
target machine. If you don't define this, the default is
`CHAR_TYPE_SIZE'.
`FLOAT_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.
`DOUBLE_TYPE_SIZE'
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.
`LONG_DOUBLE_TYPE_SIZE'
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.
`WIDEST_HARDWARE_FP_SIZE'
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 of `LONG_DOUBLE_TYPE_SIZE' is the default.
`DEFAULT_SIGNED_CHAR'
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'.
`DEFAULT_SHORT_ENUMS'
A C expression to determine whether to give an `enum' type only as
many bytes as it takes to represent the range of possible values
of that type. A nonzero value means to do that; a zero value
means all `enum' types should be allocated like `int'.
If you don't define the macro, the default is 0.
`SIZE_TYPE'
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 finally `int'. The string must
exactly match one of the data type names defined in the function
`init_decl_processing' in the file `c-decl.c'. You may not omit
`int' 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"'.
`PTRDIFF_TYPE'
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. See
`SIZE_TYPE' above for more information.
If you don't define this macro, the default is `"long int"'.
`WCHAR_TYPE'
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. See `SIZE_TYPE' above for more
information.
If you don't define this macro, the default is `"int"'.
`WCHAR_TYPE_SIZE'
A C expression for the size in bits of the data type for wide
characters. This is used in `cpp', which cannot make use of
`WCHAR_TYPE'.
`MAX_WCHAR_TYPE_SIZE'
Maximum number for the size in bits of the data type for wide
characters. If this is undefined, the default is
`WCHAR_TYPE_SIZE'. Otherwise, it is the constant value that is the
largest value that `WCHAR_TYPE_SIZE' can have at run-time. This is
used in `cpp'.
`WINT_TYPE'
A C expression for a string describing the name of the data type to
use for wide characters passed to `printf' and returned from
`getwc'. The typedef name `wint_t' is defined using the contents
of the string. See `SIZE_TYPE' above for more information.
If you don't define this macro, the default is `"unsigned int"'.
`INTMAX_TYPE'
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. See `SIZE_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 as `long long int'.
`UINTMAX_TYPE'
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. See `SIZE_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 as `long long unsigned int'.
`OBJC_INT_SELECTORS'
Define this macro if the type of Objective C selectors should be
`int'.
If this macro is not defined, then selectors should have the type
`struct objc_selector *'.
`OBJC_SELECTORS_WITHOUT_LABELS'
Define this macro if the compiler can group all the selectors
together into a vector and use just one label at the beginning of
the vector. Otherwise, the compiler must give each selector its
own assembler label.
On certain machines, it is important to have a separate label for
each selector because this enables the linker to eliminate
duplicate selectors.
`TARGET_PTRMEMFUNC_VBIT_LOCATION'
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 the `delta' 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 have
`FUNCTION_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 to `ptrmemfunc_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 to `ptrmemfunc_vbit_in_pfn'.
`TARGET_BELL'
A C constant expression for the integer value for escape sequence
`\a'.
`TARGET_BS'
`TARGET_TAB'
`TARGET_NEWLINE'
C constant expressions for the integer values for escape sequences
`\b', `\t' and `\n'.
`TARGET_VT'
`TARGET_FF'
`TARGET_CR'
C constant expressions for the integer values for escape sequences
`\v', `\f' and `\r'.
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