s2 compression panic: index out of range [0] with length 0 #929
Description
I think this may be a separate issue to #902, so opening another one.
I'm encountering a panic when compressing a specific stream of data with s2. It looks like there may be a missing bounds check when emitting repeat chunks?
panic: runtime error: index out of range [0] with length 0
goroutine 251 [running]:
github.com/klauspost/compress/s2.emitRepeat({0x140009e400b?, 0x0?, 0x0?}, 0x140009e1f78?, 0x0?)
/Users/rob/go/pkg/mod/github.com/klauspost/compress@v1.17.6/s2/encode_go.go:111 +0x1e0
github.com/klauspost/compress/s2.encodeBlockGo({0x140009e400b, 0x10004, 0x10004}, {0x140009d2008, 0x10000, 0x10007})
/Users/rob/go/pkg/mod/github.com/klauspost/compress@v1.17.6/s2/encode_all.go:146 +0x938
github.com/klauspost/compress/s2.encodeBlock(...)
/Users/rob/go/pkg/mod/github.com/klauspost/compress@v1.17.6/s2/encode_go.go:24
github.com/klauspost/compress/s2.(*Writer).encodeBlock(0x140009d2008?, {0x140009e400b?, 0x0?, 0x140003dcee0?}, {0x140009d2008?, 0x103bbf0f4?, 0x1400053e0a0?})
/Users/rob/go/pkg/mod/github.com/klauspost/compress@v1.17.6/s2/writer.go:457 +0x178
github.com/klauspost/compress/s2.(*Writer).writeFull.func1()
/Users/rob/go/pkg/mod/github.com/klauspost/compress@v1.17.6/s2/writer.go:599 +0x128
created by github.com/klauspost/compress/s2.(*Writer).writeFull in goroutine 235
/Users/rob/go/pkg/mod/github.com/klauspost/compress@v1.17.6/s2/writer.go:590 +0x388
The stream in question is 185gb, but this crash occurs fairly early within it, and reproduces every time on arm64 (Darwin, M-series)
I'll look at following up with a more straightforward test case.