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[SR-4218] [String] Non-empty strings compare equal to empty strings #374

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tbkka opened this issue Mar 10, 2017 · 7 comments
Closed

[SR-4218] [String] Non-empty strings compare equal to empty strings #374

tbkka opened this issue Mar 10, 2017 · 7 comments

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@tbkka
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@tbkka tbkka commented Mar 10, 2017

Previous ID SR-4218
Radar None
Original Reporter @tbkka
Type Bug
Status Resolved
Resolution Done
Additional Detail from JIRA
Votes 0
Component/s Standard Library, XCTest
Labels Bug, Linux
Assignee None
Priority Medium

md5: e2cfdb4ceda2c28163bf20fcffb6441d

Issue Description:

The following test succeeds on macOS, fails on Linux:

   XCTAssertNotEqual("", "\u{01}")

I believe it should succeed on all platforms.

I've seen this with the 3.0.2 release version on Ubuntu 16.04, the 3.1 snapshot from March 8 on Ubuntu 16.10, and the trunk snapshot from March 9 on Ubuntu 16.10.

@tbkka
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@tbkka tbkka commented Mar 30, 2017

This is still broken on Swift 3.1 Release on Ubuntu 16.10

@tbkka
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@tbkka tbkka commented Jun 7, 2017

This is still broken in the Swift 4.0 DEV snapshot for Ubuntu 14.04 released on May 29, 2017.

@alblue
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@alblue alblue commented Jul 4, 2017

This doesn't appear to be related to the XCTest libraries; it's pure Swift stdlib:

http://swift.sandbox.bluemix.net/#/repl/595bac27bc7c2268561f6f27

{{let empty = ""
let nonEmpty = "\u{01}"
let result = empty == nonEmpty
print(result)
}}

@alblue
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@alblue alblue commented Jul 4, 2017

The equality call shells out to this code:

https://github.com/apple/swift/blob/2b92530dfa85a017af046f3576a366e6ff914555/stdlib/public/stubs/UnicodeNormalization.cpp#L181-L215

{{
swift::_swift_stdlib_unicode_compare_utf8_utf8(const unsigned char *LeftString,
int32_t LeftLength,
const unsigned char *RightString,
int32_t RightLength) {
UCharIterator LeftIterator;
UCharIterator RightIterator;
UErrorCode ErrorCode = U_ZERO_ERROR;

uiter_setUTF8(&LeftIterator, reinterpret_cast<const char *>(LeftString), LeftLength);
uiter_setUTF8(&RightIterator, reinterpret_cast<const char *>(RightString), RightLength);

uint32_t Diff = ucol_strcollIter(GetRootCollator(),
&LeftIterator, &RightIterator, &ErrorCode);
if (U_FAILURE(ErrorCode)) {
swift::crash("ucol_strcollIter: Unexpected error doing utf8<->utf8 string comparison.");
}
return Diff;
}
}}

I suspect what's happening is the control characters (<20) are being handled in a different way in the iterator, which is why the result is being discarded. Compare:

print("" == "\u{19}") // true
print("" == "\u{20}") // false

@tbkka
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@tbkka tbkka commented Feb 14, 2018

This is still broken in the current Swift 4.1 DEV snapshots.

@Dante-Broggi
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@Dante-Broggi Dante-Broggi commented Jul 18, 2018

Has this been fixed? If so this should be closed.

@tbkka
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@tbkka tbkka commented Jul 18, 2018

I no longer see this in 4.2. 🙂

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@shahmishal shahmishal transferred this issue from apple/swift May 9, 2022
This issue was closed.
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