C.sizeof_struct_stat.

A C function may be declared in the Go file with a parameter type of
the special name _GoString_. This function may be called with an
ordinary Go string value. The string length, and a pointer to the
string contents, may be accessed by calling the C functions

	size_t _GoStringLen(_GoString_ s);
	const char *_GoStringPtr(_GoString_ s);

These functions are only available in the preamble, not in other C

pkg debug/dwarf, method (*LineReader) SeekPC(uint64, *LineEntry) error
pkg debug/dwarf, method (*LineReader) Tell() LineReaderPos
pkg debug/dwarf, method (*Reader) AddressSize() int
pkg debug/dwarf, method (Class) GoString() string
pkg debug/dwarf, method (Class) String() string
pkg debug/dwarf, type Class int
pkg debug/dwarf, type Field struct, Class Class
pkg debug/dwarf, type LineEntry struct

pkg debug/elf, const SHF_COMPRESSED = 2048
pkg debug/elf, const SHF_COMPRESSED SectionFlag
pkg debug/elf, method (CompressionType) GoString() string
pkg debug/elf, method (CompressionType) String() string
pkg debug/elf, method (R_MIPS) GoString() string
pkg debug/elf, method (R_MIPS) String() string
pkg debug/elf, type Chdr32 struct
pkg debug/elf, type Chdr32 struct, Addralign uint32

			if c.incompleteStructs[tag] {
				tt.Go = c.Ident(incomplete)
			}
			typedef[name.Name] = &tt
		}

	case *dwarf.TypedefType:
		// Record typedef for printing.
		if dt.Name == "_GoString_" {
			// Special C name for Go string type.
			// Knows string layout used by compilers: pointer plus length,
			// which rounds up to 2 pointers after alignment.
			t.Go = c.string
			t.Size = c.ptrSize * 2

pkg debug/elf, method (ProgType) String() string
pkg debug/elf, method (R_386) GoString() string
pkg debug/elf, method (R_386) String() string
pkg debug/elf, method (R_ALPHA) GoString() string
pkg debug/elf, method (R_ALPHA) String() string
pkg debug/elf, method (R_ARM) GoString() string
pkg debug/elf, method (R_ARM) String() string
pkg debug/elf, method (R_PPC) GoString() string

}

int
returnAfterGrowFromGo(void)
{
	extern int goReturnVal(void);
	return goReturnVal();
}

void
callGoWithString(void)
{
	extern void goWithString(GoString);
	const char *str = "string passed from C to Go";
	goWithString((GoString){str, strlen(str)});

pkg debug/elf, const STV_HIDDEN = 2
pkg debug/elf, const STV_INTERNAL = 1
pkg debug/elf, const STV_PROTECTED = 3
pkg debug/elf, const Sym32Size = 16
pkg debug/elf, const Sym64Size = 24
pkg debug/elf, method (*File) DynString(DynTag) ([]string, error)
pkg debug/elf, type FileHeader struct, Entry uint64
pkg debug/macho, const Cpu386 = 7
pkg debug/macho, const CpuAmd64 = 16777223
pkg debug/macho, const LoadCmdDylib = 12

		return os.ErrInvalid
	}
	p := C.CString(s)
	defer C.free(unsafe.Pointer(p))
	if C.mpz_set_str(&z.i[0], p, C.int(base)) < 0 {
		return os.ErrInvalid
	}
	return nil
}

// String returns the decimal representation of z.
func (z *Int) String() string {
	if z == nil {
		return "nil"
	}
	z.doinit()
	p := C.mpz_get_str(nil, 10, &z.i[0])
	s := C.GoString(p)
	C.free(unsafe.Pointer(p))
	return s

pkg debug/macho, method (RelocTypeARM) GoString() string
pkg debug/macho, method (RelocTypeARM) String() string
pkg debug/macho, method (RelocTypeARM64) GoString() string
pkg debug/macho, method (RelocTypeARM64) String() string
pkg debug/macho, method (RelocTypeGeneric) GoString() string
pkg debug/macho, method (RelocTypeGeneric) String() string
pkg debug/macho, method (RelocTypeX86_64) GoString() string

pkg debug/elf, const R_AARCH64_TLS_TPREL64 R_AARCH64
pkg debug/elf, const R_AARCH64_TSTBR14 = 279
pkg debug/elf, const R_AARCH64_TSTBR14 R_AARCH64
pkg debug/elf, method (R_AARCH64) GoString() string
pkg debug/elf, method (R_AARCH64) String() string
pkg debug/elf, type R_AARCH64 int