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spec: inconsistent Behavior Dividing by 0.0 using Static vs Variable assignment #23524

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TopherGopher opened this issue Jan 23, 2018 · 2 comments
Closed

spec: inconsistent Behavior Dividing by 0.0 using Static vs Variable assignment #23524

TopherGopher opened this issue Jan 23, 2018 · 2 comments
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@TopherGopher
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TopherGopher commented Jan 23, 2018 •
edited

Please answer these questions before submitting your issue. Thanks!

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

go version go1.8.3 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/usterch/src/GO"
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/jf/ggd1wkrj6wn4zlqgt10xh66c5sxxm7/T/go-build295819013=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"

What did you do?

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.
Two links:
This compiles and runs successfully through: https://play.golang.org/p/SHkSuvdSoX5
This demonstrates the inconsistent behavior if I use a variable as the denominator: https://play.golang.org/p/_IfEAM4XsQu

What did you expect to see?

I should see the same behavior if I try to use a variable as when I use a constant.

What did you see instead?

Either both lines should fail, or neither should.

Related Issue

#10006
@ALTree
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ALTree commented Jan 23, 2018 •
edited

This behaviour is consistent with the spec. The spec forbids constant division by zero, but we have never generated compile-time errors for variables.

Regarding the run-time behaviour of your fist code snippet, note that

the result of a floating-point or complex division by zero is not specified beyond the IEEE-754 standard; whether a run-time panic occurs is implementation-specific.

So not even a crash at run-time is mandatory. Generating an IEEE-754 +Inf is allowed.

@ALTree ALTree changed the title Inconsistent Behavior Dividing by 0.0 using Static vs Variable assignment spec: inconsistent Behavior Dividing by 0.0 using Static vs Variable assignment Jan 23, 2018
@ianlancetaylor
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This is working as documented. Closing.

If you want to discuss this, please use a forum. See https://golang.org/wiki/Questions. Thanks.

@golang golang locked and limited conversation to collaborators Jan 23, 2019
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@TopherGopher @ianlancetaylor @ALTree @gopherbot