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Printing addresses of empty structs affects their values (https://github.com/golang/go/issues/25699)
From https://godbolt.org/
x86 gc 1.10.1
package main
import (
"fmt"
)
func main() {
var a, b struct{}
fmt.Println(&a, &b)
fmt.Println(&a == &b) // true
} text "".main(SB), $120-0
movq (TLS), CX
cmpq SP, 16(CX)
jls 258
subq $120, SP
movq BP, 112(SP)
leaq 112(SP), BP
funcdata $0, gclocals·f6bd6b3389b872033d462029172c8612(SB)
funcdata $1, gclocals·1044ffefec669683581bed15df4f1d5b(SB)
leaq type.struct {}(SB), AX
movq AX, (SP)
pcdata $0, $0
call runtime.newobject(SB)
movq 8(SP), AX
movq AX, "".&a+56(SP)
leaq type.struct {}(SB), CX
movq CX, (SP)
pcdata $0, $1
call runtime.newobject(SB)
movq 8(SP), AX
movq AX, "".&b+48(SP)
xorps X0, X0
movups X0, ""..autotmp_4+80(SP)
movups X0, ""..autotmp_4+96(SP)
leaq type.*struct {}(SB), CX
movq CX, ""..autotmp_4+80(SP)
movq "".&a+56(SP), DX
movq DX, ""..autotmp_4+88(SP)
movq CX, ""..autotmp_4+96(SP)
movq AX, ""..autotmp_4+104(SP)
leaq ""..autotmp_4+80(SP), CX
movq CX, (SP)
movq $2, 8(SP)
movq $2, 16(SP)
pcdata $0, $2
call fmt.Println(SB)
xorps X0, X0
movups X0, ""..autotmp_7+64(SP)
leaq type.bool(SB), AX
movq AX, ""..autotmp_7+64(SP)
movq "".&a+56(SP), AX
movq "".&b+48(SP), CX
cmpq AX, CX
seteq AL
movblzx AL, AX
leaq runtime.staticbytes(SB), CX
addq CX, AX
movq AX, ""..autotmp_7+72(SP)
leaq ""..autotmp_7+64(SP), AX
movq AX, (SP)
movq $1, 8(SP)
movq $1, 16(SP)
pcdata $0, $3
call fmt.Println(SB)
movq 112(SP), BP
addq $120, SP
ret
nop
pcdata $0, $-1
call runtime.morestack_noctxt(SB)
jmp 0
text "".init(SB), $8-0
movq (TLS), CX
cmpq SP, 16(CX)
jls 84
subq $8, SP
movq BP, (SP)
leaq (SP), BP
funcdata $0, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
funcdata $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
movblzx "".initdone·(SB), AX
cmpb AL, $1
jls 47
movq (SP), BP
addq $8, SP
ret
jne 56
pcdata $0, $0
call runtime.throwinit(SB)
undef
movb $1, "".initdone·(SB)
pcdata $0, $0
call fmt.init(SB)
movb $2, "".initdone·(SB)
movq (SP), BP
addq $8, SP
ret
nop
pcdata $0, $-1
call runtime.morestack_noctxt(SB)
jmp 0
text type..hash.[2]interface {}(SB), DUPOK, $40-24
movq (TLS), CX
cmpq SP, 16(CX)
jls 103
subq $40, SP
movq BP, 32(SP)
leaq 32(SP), BP
funcdata $0, gclocals·d4dc2f11db048877dbc0f60a22b4adb3(SB)
funcdata $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
xorl AX, AX
movq "".h+56(SP), CX
jmp 82
movq AX, "".i+24(SP)
shlq $4, AX
movq "".p+48(SP), BX
addq BX, AX
movq AX, (SP)
movq CX, 8(SP)
pcdata $0, $0
call runtime.nilinterhash(SB)
movq 16(SP), CX
movq "".i+24(SP), AX
incq AX
cmpq AX, $2
jlt 38
movq CX, "".~r2+64(SP)
movq 32(SP), BP
addq $40, SP
ret
nop
pcdata $0, $-1
call runtime.morestack_noctxt(SB)
jmp 0
text type..eq.[2]interface {}(SB), DUPOK, $48-24
movq (TLS), CX
cmpq SP, 16(CX)
jls 155
subq $48, SP
movq BP, 40(SP)
leaq 40(SP), BP
funcdata $0, gclocals·8f9cec06d1ae35cc9900c511c5e4bdab(SB)
funcdata $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
xorl AX, AX
jmp 46
movq ""..autotmp_8+32(SP), CX
leaq 1(CX), AX
cmpq AX, $2
jge 140
movq AX, CX
shlq $4, AX
movq "".p+56(SP), DX
movq 8(AX)(DX*1), BX
movq (AX)(DX*1), SI
movq "".q+64(SP), DI
movq 8(AX)(DI*1), R8
movq (AX)(DI*1), AX
cmpq SI, AX
jne 125
movq CX, ""..autotmp_8+32(SP)
movq SI, (SP)
movq BX, 8(SP)
movq R8, 16(SP)
pcdata $0, $0
call runtime.efaceeq(SB)
movblzx 24(SP), AX
testb AL, AL
jne 37
movb $0, "".~r2+72(SP)
movq 40(SP), BP
addq $48, SP
ret
movb $1, "".~r2+72(SP)
movq 40(SP), BP
addq $48, SP
ret
nop
pcdata $0, $-1
call runtime.morestack_noctxt(SB)
jmp 0From https://godbolt.org/
x86 gc 1.10.1
package main
import (
"fmt"
)
func main() {
var a, b struct{}
// fmt.Println(&a, &b)
fmt.Println(&a == &b) // false
} text "".main(SB), $72-0
movq (TLS), CX
cmpq SP, 16(CX)
jls 111
subq $72, SP
movq BP, 64(SP)
leaq 64(SP), BP
funcdata $0, gclocals·69c1753bd5f81501d95132d08af04464(SB)
funcdata $1, gclocals·e226d4ae4a7cad8835311c6a4683c14f(SB)
xorps X0, X0
movups X0, ""..autotmp_2+48(SP)
leaq type.bool(SB), AX
movq AX, ""..autotmp_2+48(SP)
xorl AX, AX
movblzx AL, AX
leaq runtime.staticbytes(SB), CX
addq CX, AX
movq AX, ""..autotmp_2+56(SP)
leaq ""..autotmp_2+48(SP), AX
movq AX, (SP)
movq $1, 8(SP)
movq $1, 16(SP)
pcdata $0, $1
call fmt.Println(SB)
movq 64(SP), BP
addq $72, SP
ret
nop
pcdata $0, $-1
call runtime.morestack_noctxt(SB)
jmp 0
text "".init(SB), $8-0
movq (TLS), CX
cmpq SP, 16(CX)
jls 84
subq $8, SP
movq BP, (SP)
leaq (SP), BP
funcdata $0, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
funcdata $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
movblzx "".initdone·(SB), AX
cmpb AL, $1
jls 47
movq (SP), BP
addq $8, SP
ret
jne 56
pcdata $0, $0
call runtime.throwinit(SB)
undef
movb $1, "".initdone·(SB)
pcdata $0, $0
call fmt.init(SB)
movb $2, "".initdone·(SB)
movq (SP), BP
addq $8, SP
ret
nop
pcdata $0, $-1
call runtime.morestack_noctxt(SB)
jmp 0From https://godbolt.org/
x86 gc 1.10.1
package main
import (
"fmt"
)
func main() {
var a, b struct{}
fmt.Println(&a == &b) // true. wtf
fmt.Printf("a: %p, b: %p\n", &a, &b)
} text "".main(SB), $136-0
movq (TLS), CX
leaq -8(SP), AX
cmpq AX, 16(CX)
jls 299
subq $136, SP
movq BP, 128(SP)
leaq 128(SP), BP
funcdata $0, gclocals·f6bd6b3389b872033d462029172c8612(SB)
funcdata $1, gclocals·fc04784923b15e2be0d0059277510785(SB)
leaq type.struct {}(SB), AX
movq AX, (SP)
pcdata $0, $0
call runtime.newobject(SB)
movq 8(SP), AX
movq AX, "".&a+72(SP)
leaq type.struct {}(SB), CX
movq CX, (SP)
pcdata $0, $1
call runtime.newobject(SB)
movq 8(SP), AX
movq AX, "".&b+64(SP)
xorps X0, X0
movups X0, ""..autotmp_4+80(SP)
leaq type.bool(SB), CX
movq CX, ""..autotmp_4+80(SP)
movq "".&a+72(SP), CX
cmpq CX, AX
seteq DL
movblzx DL, DX
leaq runtime.staticbytes(SB), BX
addq BX, DX
movq DX, ""..autotmp_4+88(SP)
leaq ""..autotmp_4+80(SP), DX
movq DX, (SP)
movq $1, 8(SP)
movq $1, 16(SP)
pcdata $0, $2
call fmt.Println(SB)
xorps X0, X0
movups X0, ""..autotmp_6+96(SP)
movups X0, ""..autotmp_6+112(SP)
leaq type.*struct {}(SB), AX
movq AX, ""..autotmp_6+96(SP)
movq "".&a+72(SP), CX
movq CX, ""..autotmp_6+104(SP)
movq AX, ""..autotmp_6+112(SP)
movq "".&b+64(SP), AX
movq AX, ""..autotmp_6+120(SP)
leaq go.string."a: %p, b: %p\n"(SB), AX
movq AX, (SP)
movq $13, 8(SP)
leaq ""..autotmp_6+96(SP), AX
movq AX, 16(SP)
movq $2, 24(SP)
movq $2, 32(SP)
pcdata $0, $3
call fmt.Printf(SB)
movq 128(SP), BP
addq $136, SP
ret
nop
pcdata $0, $-1
call runtime.morestack_noctxt(SB)
jmp 0
text "".init(SB), $8-0
movq (TLS), CX
cmpq SP, 16(CX)
jls 84
subq $8, SP
movq BP, (SP)
leaq (SP), BP
funcdata $0, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
funcdata $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
movblzx "".initdone·(SB), AX
cmpb AL, $1
jls 47
movq (SP), BP
addq $8, SP
ret
jne 56
pcdata $0, $0
call runtime.throwinit(SB)
undef
movb $1, "".initdone·(SB)
pcdata $0, $0
call fmt.init(SB)
movb $2, "".initdone·(SB)
movq (SP), BP
addq $8, SP
ret
nop
pcdata $0, $-1
call runtime.morestack_noctxt(SB)
jmp 0
text type..hash.[2]interface {}(SB), DUPOK, $40-24
movq (TLS), CX
cmpq SP, 16(CX)
jls 103
subq $40, SP
movq BP, 32(SP)
leaq 32(SP), BP
funcdata $0, gclocals·d4dc2f11db048877dbc0f60a22b4adb3(SB)
funcdata $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
xorl AX, AX
movq "".h+56(SP), CX
jmp 82
movq AX, "".i+24(SP)
shlq $4, AX
movq "".p+48(SP), BX
addq BX, AX
movq AX, (SP)
movq CX, 8(SP)
pcdata $0, $0
call runtime.nilinterhash(SB)
movq 16(SP), CX
movq "".i+24(SP), AX
incq AX
cmpq AX, $2
jlt 38
movq CX, "".~r2+64(SP)
movq 32(SP), BP
addq $40, SP
ret
nop
pcdata $0, $-1
call runtime.morestack_noctxt(SB)
jmp 0
text type..eq.[2]interface {}(SB), DUPOK, $48-24
movq (TLS), CX
cmpq SP, 16(CX)
jls 155
subq $48, SP
movq BP, 40(SP)
leaq 40(SP), BP
funcdata $0, gclocals·8f9cec06d1ae35cc9900c511c5e4bdab(SB)
funcdata $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
xorl AX, AX
jmp 46
movq ""..autotmp_8+32(SP), CX
leaq 1(CX), AX
cmpq AX, $2
jge 140
movq AX, CX
shlq $4, AX
movq "".p+56(SP), DX
movq 8(AX)(DX*1), BX
movq (AX)(DX*1), SI
movq "".q+64(SP), DI
movq 8(AX)(DI*1), R8
movq (AX)(DI*1), AX
cmpq SI, AX
jne 125
movq CX, ""..autotmp_8+32(SP)
movq SI, (SP)
movq BX, 8(SP)
movq R8, 16(SP)
pcdata $0, $0
call runtime.efaceeq(SB)
movblzx 24(SP), AX
testb AL, AL
jne 37
movb $0, "".~r2+72(SP)
movq 40(SP), BP
addq $48, SP
ret
movb $1, "".~r2+72(SP)
movq 40(SP), BP
addq $48, SP
ret
nop
pcdata $0, $-1
call runtime.morestack_noctxt(SB)
jmp 0
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