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cmd/gc: converting len(slice) value to non-fitting numeric types should result in overflow error #33643

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nrvnrvn opened this issue Aug 14, 2019 · 4 comments

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@nrvnrvn
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@nrvnrvn nrvnrvn commented Aug 14, 2019

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

$ go version
go version go1.12.7

Does this issue reproduce with the latest release?

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
CC="clang"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_ENABLED="1"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
CXX="clang++"
GCCGO="gccgo"
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/lol/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/fq/v153jfj15jz73k94n8mzycl40000gn/T/go-build186400384=/tmp/go-build -gno-record-gcc-switches -fno-common"
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOMOD="/mycoolproject/go.mod"
GOOS="darwin"
GOPATH="/Users/lol/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/Cellar/go/1.12.7/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.12.7/libexec/pkg/tool/darwin_amd64"
PKG_CONFIG="pkg-config"

What did you do?

https://play.golang.org/p/4RP50Tv00i8

What did you expect to see?

https://play.golang.org/p/cvwZ7P8Fa_q

What did you see instead?

overflowing value is converted to 0

@zephyrtronium
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@zephyrtronium zephyrtronium commented Aug 14, 2019

This is closely related to #30613 and the various issues linked therefrom. That discussion might benefit from your use case for a checked uint8 type.

@andybons andybons changed the title converting len(slice) value to non-fitting numeric types should result in overflow error cmd/gc: converting len(slice) value to non-fitting numeric types should result in overflow error Aug 15, 2019
@andybons
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@andybons andybons commented Aug 15, 2019

@nrvnrvn are you expecting an error at compile time or runtime?

@nrvnrvn
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@nrvnrvn nrvnrvn commented Aug 15, 2019

Good question. I would expect a runtime error.

@andybons
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@andybons andybons commented Aug 15, 2019

At first this seems like a dupe of #31500. Would you agree?

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