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[SR-3535] divideWithOverflow gives Overflow error with edge case #46123

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swift-ci opened this issue Jan 4, 2017 · 3 comments
Closed

[SR-3535] divideWithOverflow gives Overflow error with edge case #46123

swift-ci opened this issue Jan 4, 2017 · 3 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself

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@swift-ci
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swift-ci commented Jan 4, 2017

Previous ID SR-3535
Radar None
Original Reporter PeterWAWood (JIRA User)
Type Bug
Status Closed
Resolution Done
Environment

MacBook 2.5ghz Intel Core I7, macOS 10.12.2, Xcode 8.2.1

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug
Assignee None
Priority Medium

md5: ed4206a13cf1c4db0bfb3f93be5acea8

relates to:

  • SR-5964 dividedReportingOverflow may fail to compile for calculations that overflow

Issue Description:

The statement - Int.divideWithOverflow(Int.min, -1) - will give an overflow error.

Here is an extract of playground output when the statement is entered:

Playground execution failed: error: MyPlayground.playground:1:5: error: division     '-9223372036854775808 / -1' results in an overflow
Int.divideWithOverflow(Int.min, -1)
    ^

* thread #​1: tid = 0x2d8fad, 0x0000000103035360 com.apple.dt.Xcode.PlaygroundStub-macosx`executePlayground, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1

I checked on the Swift ML and was advised that this is expected. I am raising this issue as I feel that this "exception" needs to be documented.
@belkadan
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belkadan commented Jan 4, 2017

cc @dabrahams, @natecook1000

@dabrahams
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IMO, this should not be expected. The error is a compile-time error from a function that is supposed to report at runtime whether there would be an overflow. Failing to compile this is akin to generating an error on the expression 1+1 == 2 just because its result is known to be true at compile-time.

@belkadan
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belkadan commented Jan 4, 2017

Oh, sorry! I misread and thought it was a run-time error. Yes, the compiler should allow this when calling divideWithOverflow rather than plain /.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself
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@dabrahams @belkadan @swift-ci