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cmd/compile: "bad code" with very large return value #20780

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josharian opened this issue Jun 24, 2017 · 3 comments

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commented Jun 24, 2017

package p

type S struct {
	i interface {
		f() [107374100]int
	}
}

Compiling this with 1.9beta1 results in:

$ go tool compile x.go
compile: bad code

Same for 1.8.

Unlike its brethren, #20779 and #20778, the size of the return value here seems reasonable enough that it might be worth briefly investigating for 1.10, just in case.

Found by go-fuzz.

@josharian josharian added this to the Go1.10 milestone Jun 24, 2017

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commented Jul 10, 2017

Error is coming from here src/cmd/internal/obj/pcln.go
But in general, it's problem of offset, it's overflowing int32:

<autogenerated>:1:0: offset too large in 00022 (<autogenerated>:1)      MOVQ    BP, -2147483656(SP)
<autogenerated>:1:0: offset too large in 00030 (<autogenerated>:1)      LEAQ    -2147483656(SP), BP
<autogenerated>:1:0: offset too large in 00096 (<autogenerated>:1)      MOVQ    DX, ""..autotmp_2-3221225472(SP)
<autogenerated>:1:0: offset too large in 00109 (<autogenerated>:1)      LEAQ    ""..autotmp_2-3221225464(SP), DI
<autogenerated>:1:0: offset too large in 00125 (<autogenerated>:1)      MOVQ    ""..autotmp_2-3221225472(SP), DX
<autogenerated>:1:0: offset too large in 00149 (<autogenerated>:1)      LEAQ    ""..autotmp_2-3221225464(SP), SI
<autogenerated>:1:0: offset too large in 00165 (<autogenerated>:1)      MOVQ    -2147483656(SP), BP

@bradfitz bradfitz added the NeedsFix label Nov 29, 2017

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commented Nov 29, 2017

More detail at Go tip, but still present:

bradfitz@gdev:~$ go version
go version devel +992ce90 Wed Nov 29 03:24:52 2017 +0000 linux/amd64
bradfitz@gdev:~$ go tool compile x.go
<autogenerated>:1:0: overflow in spadj: 0 + 1717985616 = 1717985616
compile: bad code

It's been this way for 2 releases, so might as well be 3, sorry.

/cc @mdempsky

@bradfitz bradfitz modified the milestones: Go1.10, Go1.11 Nov 29, 2017

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commented May 29, 2018

Change https://golang.org/cl/115195 mentions this issue: cmd/compile: include callee args section when checking frame too large

@gopherbot gopherbot closed this in 06b3260 Jun 2, 2018

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