Address Space Attributes

Microsoft-specific modifiers

Pointer Size Address Space Attributes

Requires -fms-extensions

Attributes that define the size of a pointer type.

Attribute	X86_32	X86_64
__ptr32	Nop	Extended
__ptr64	Truncated	Nop

Pointer Sign Extension Attributes

Requires -fms-extensions

Attributes that define the extension behavior of a pointer attributed with __ptr32 when cast to 64 bits.

Attribute	Extension
__sptr	Sign extended
__uptr	Zero extended

Segment Register Relative Pointer Attributes

Memory references to specified segments
Remove address space builtin function
address-space

Segment Register	__attribute__((address_space(X)))	Attribute Macro	Test Macro
GS	__attribute__((address_space(256)))	__seg_gs	__SEG_GS
FS	__attribute__((address_space(257)))	__seg_fs	__SEG_FS
SS	__attribute__((address_space(258)))

Pointers with these attributes will be relative to the corresponding segment register. The attribute macros expand to the corresponding __attribute__((address_space(X))) attribute and the test macro indicates support, this is for GCC compatibility.