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cmd/compile: panic: interface conversion: interface is nil, not gc.SliceType #15530

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rhysh opened this issue May 3, 2016 · 4 comments
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cmd/compile: panic: interface conversion: interface is nil, not gc.SliceType #15530

rhysh opened this issue May 3, 2016 · 4 comments
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Go1.7

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@rhysh
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rhysh commented May 3, 2016

What version of Go are you using (go version)?

$ go version
go version devel +15f7a66 Tue May 3 14:57:06 2016 +0000 darwin/amd64

What did you do?

go build -o /tmp/command ./cmd/command

What did you expect to see?

I expected the package to compile and link successfully, as it does with go1.5.4 and go1.6.2.

What did you see instead?

cmd/compile panicked. Within my (closed-source) project, there are two packages that cause a panic in compile. One of them is a main package, the other a non-main package.

I eliminated lines in those two packages until the panic went away—the critical lines in both packages were a call to functions in a third (non-main) package that 1) successfully compiles, and 2) contains other functions with similar signatures that are called from elsewhere in the project without causing compiler panics.

I bisected the Go toolchain, which indicated 7538b1d—enabling the binary export format—as the first commit with this bug. Adding -gcflags="-newexport=0" to the command line when compiling with 15f7a66 results in a successful build.

It's not (yet) much to go on, particularly since I'm not able to share the code. What information would be most useful for debugging?

panic: interface conversion: interface is nil, not gc.SliceType

goroutine 1 [running]:
panic(0x47ac80, 0x820f32c40)
        /usr/local/go/src/runtime/panic.go:500 +0x18c
cmd/compile/internal/gc.(*Type).Elem(0x820f3aa50, 0x820e6d090)
        /usr/local/go/src/cmd/compile/internal/gc/type.go:737 +0x1c4
cmd/compile/internal/gc.eqtype1(0x820e6d180, 0x820f3aa50, 0x820d59978, 0x0)
        /usr/local/go/src/cmd/compile/internal/gc/subr.go:715 +0x758
cmd/compile/internal/gc.eqtype1(0x820e6dae0, 0x820f3b400, 0x820d59978, 0x2)
        /usr/local/go/src/cmd/compile/internal/gc/subr.go:688 +0x2bc
cmd/compile/internal/gc.eqtype1(0x820e6d130, 0x820f3aaa0, 0x820d59978, 0xfffffffffffffff2)
        /usr/local/go/src/cmd/compile/internal/gc/subr.go:669 +0x558
cmd/compile/internal/gc.Eqtype(0x820e6d130, 0x820f3aaa0, 0x820e44c10)
        /usr/local/go/src/cmd/compile/internal/gc/subr.go:629 +0x34
cmd/compile/internal/gc.importtype(0x820e6d090, 0x820f3aaa0)
        /usr/local/go/src/cmd/compile/internal/gc/export.go:570 +0x25c
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0xffffffffffffff14)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:342 +0x15b
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0x8207c3338)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:397 +0xaf1
cmd/compile/internal/gc.(*importer).param(0x820d8ac60, 0x0, 0x1)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:553 +0x30
cmd/compile/internal/gc.(*importer).paramList(0x820d8ac60, 0x0, 0x0, 0x0)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:546 +0xa0
cmd/compile/internal/gc.(*importer).method(0x820d8ac60, 0x820f3c630)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:509 +0x86
cmd/compile/internal/gc.(*importer).methodList(0x820d8ac60, 0x0, 0x820f110e0, 0x820d829a0)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:498 +0x85
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0x820e76870)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:423 +0xf73
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0x820efaf50)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:341 +0x138
cmd/compile/internal/gc.(*importer).field(0x820d8ac60, 0x2)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:469 +0x4b
cmd/compile/internal/gc.(*importer).fieldList(0x820d8ac60, 0xffffffffffffff16, 0x820f11040, 0x6)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:459 +0x85
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0x820f10fa0)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:406 +0xb74
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0xffffffffffffff12)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:341 +0x138
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0xffffffffffffff14)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:410 +0xedb
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0x820f10e10)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:397 +0xaf1
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0x820f122a0)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:429 +0xcc3
cmd/compile/internal/gc.(*importer).field(0x820d8ac60, 0x1)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:469 +0x4b
cmd/compile/internal/gc.(*importer).fieldList(0x820d8ac60, 0xffffffffffffff16, 0x820f10cd0, 0x20)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:459 +0x85
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0x820f10c30)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:406 +0xb74
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0x820f121c0)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:341 +0x138
cmd/compile/internal/gc.(*importer).field(0x820d8ac60, 0x3)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:469 +0x4b
cmd/compile/internal/gc.(*importer).fieldList(0x820d8ac60, 0xffffffffffffff16, 0x820f10be0, 0x6)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:459 +0x85
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0x820f10b40)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:406 +0xb74
cmd/compile/internal/gc.(*importer).typ(0x820d8ac60, 0x8207a7c70)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:341 +0x138
cmd/compile/internal/gc.(*importer).obj(0x820d8ac60, 0xfffffffffffffffd)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:250 +0x903
cmd/compile/internal/gc.Import(0x8207aa2a0)
        /usr/local/go/src/cmd/compile/internal/gc/bimport.go:88 +0x338
cmd/compile/internal/gc.importfile(0x820bae800, 0x0, 0x0, 0x0)
        /usr/local/go/src/cmd/compile/internal/gc/main.go:825 +0x902
cmd/compile/internal/gc.(*parser).importdcl(0x820bae7e0)
        /usr/local/go/src/cmd/compile/internal/gc/parser.go:341 +0x160
cmd/compile/internal/gc.(*parser).import_(0x820bae7e0)
        /usr/local/go/src/cmd/compile/internal/gc/parser.go:300 +0x67
cmd/compile/internal/gc.(*parser).file(0x820bae7e0)
        /usr/local/go/src/cmd/compile/internal/gc/parser.go:268 +0x54
cmd/compile/internal/gc.parse_file(0x8207aa240)
        /usr/local/go/src/cmd/compile/internal/gc/parser.go:31 +0x4a
cmd/compile/internal/gc.Main()
        /usr/local/go/src/cmd/compile/internal/gc/main.go:331 +0x144e
cmd/compile/internal/amd64.Main()
        /usr/local/go/src/cmd/compile/internal/amd64/galign.go:96 +0x381
main.main()
        /usr/local/go/src/cmd/compile/main.go:33 +0x286
@josharian
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cc @griesemer @mdempsky

@josharian josharian added this to the Go1.7 milestone May 3, 2016
@griesemer griesemer self-assigned this May 6, 2016
@griesemer
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@rhysh Can you please confirm that this still crashes with the latest tip (I have fixed another import bug today, and I'm about to fix another one, likely). Thanks.

@rhysh
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rhysh commented May 6, 2016

Thanks @griesemer , it looks like this is fixed. I'm unable to reproduce the crash with 2e32efc (go version devel +2e32efc Fri May 6 05:50:02 2016 +0000 darwin/amd64)

@rhysh rhysh closed this as completed May 6, 2016
@rhysh
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rhysh commented May 6, 2016

This was fixed by commit 8650c23

@golang golang locked and limited conversation to collaborators May 6, 2017
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