asm newbie questions: missing stackmap

[chai2010]

The asm function `Sum` try call a Go function `sum`,

when the `sum` need morestack, it crashed:

// main.go

func main() {

println(Sum(100))

println(Sum(100 * 1000)) // panic!

}

func Sum(n int) int

func sum(i, j int) int {

if i <= 0 {

return j

}

return sum(i-1, i+j)

}

// main_amd64.s

TEXT ·Sum(SB), $24-16

MOVQ n+0(FP), AX

MOVQ AX, 0(SP)

MOVQ $0, 8(SP)

CALL ·sum(SB)

MOVQ 16(SP), AX

MOVQ AX, ret+8(FP)

RET

panic message:

Sum(100): 50005000

runtime: frame ... untyped locals 0xc042233e88+0x18

fatal error: missing stackmap

runtime stack:

runtime.throw(0x467c4b, 0x10)

C:/go/go1.7.windows-amd64/src/runtime/panic.go:566 +0x9c

runtime.adjustframe(0x6fb40, 0x6fc38, 0x6f901)

C:/go/go1.7.windows-amd64/src/runtime/stack.go:660 +0x7d2

runtime.gentraceback(0xffffffffffffffff, 0xc0421b52b0, 0x0, 0xc04201c000, 0x0, 0x0, 0x7fffffff, 0x46d898, 0x6fc38, 0x0, ...)

C:/go/go1.7.windows-amd64/src/runtime/traceback.go:378 +0x10aa

runtime.copystack(0xc04201c000, 0x100000, 0x6fe01)

C:/go/go1.7.windows-amd64/src/runtime/stack.go:902 +0x388

runtime.newstack()

C:/go/go1.7.windows-amd64/src/runtime/stack.go:1070 +0x37e

runtime.morestack()

C:/go/go1.7.windows-amd64/src/runtime/asm_amd64.s:366 +0x87

...

Thanks!

--

https://github.com/golang-china/gopl-zh

https://github.com/golang-china

https://github.com/chai2010

[Ian Lance Taylor]

If an assembler function can call into Go, it needs to provide a stack
map that tells the Go stack unwinder which local variables on the
stack are pointers. In this case none of them are pointers, so you
can just add NO_LOCAL_POINTERS as defined in runtime/funcdata.h.

Ian