Regex Matches Count gives ArgumentOutOfRangeException (regression)

[AlbertoMonteiro]

Description

Just run this code with dotnet 7.0.100-preview.1.22110.4 and it will break

_ = Regex.Matches("bar\n", @"(?m)^[^a]a", 0).Count

Reproduction Steps

Clone this project: https://github.com/AlbertoMonteiro/RegexIssueDotnet7Preview1
Then dotnet run

Expected behavior

The Count should return 1

Actual behavior

Throws System.ArgumentOutOfRangeException

Regression?

On dotnet 6 it works fine

Known Workarounds

Adding an \0 to the end of the string that ends with \n doesnt throw

_ = Regex.Matches("bar\n\0", @"(?m)^[^a]a", 0).Count

Returns properly 1

Configuration

No response

Other information

No response

[ghost]

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Issue Details

---

Description

Just run this code with dotnet 7.0.100-preview.1.22110.4 and it will break

_ = Regex.Matches("bar\n", @"(?m)^[^a]a", 0).Count

Reproduction Steps

Clone this project: https://github.com/AlbertoMonteiro/RegexIssueDotnet7Preview1
Then dotnet run

Expected behavior

The Count should return 1

Actual behavior

Throws System.ArgumentOutOfRangeException

Regression?

On dotnet 6 it works fine

Known Workarounds

No response

Configuration

No response

Other information

No response

Author:	AlbertoMonteiro
Assignees:	-
Labels:	area-System.Text.RegularExpressions, untriaged
Milestone:	-

[stephentoub]

Thanks for the great bug report. We're missing a length check after we optimize for a beginning-of-line anchor and jump to the next \n.

[firasdib]

For what its worth, I was unable to verify that this fix worked, running the nightly build (found here https://github.com/dotnet/aspnetcore/blob/main/docs/DailyBuilds.md). I still see the same error.

[stephentoub]

I was unable to verify that this fix worked, running the nightly build (found here https://github.com/dotnet/aspnetcore/blob/main/docs/DailyBuilds.md). I still see the same error.

What version of the runtime is this using? The PR that fixed this issue added as tests the exact offending inputs:
https://github.com/dotnet/runtime/pull/66216/files#diff-c58e67b58388ef7fa39f05ef7548fd1a3af4473457a150cac9bebe1e8ad0dadbR247-R278

[firasdib]

This is the output I get is:

> ~/projects/dotnet/dotnet --version
7.0.100-preview.3.22165.3

Running Linux 5.16.11-2-MANJARO x86_64

[stephentoub]

What do you see for .NET 7 for dotnet --list-runtimes?

[firasdib]

Here's the output from that

> ~/projects/dotnet/dotnet --list-runtimes
Microsoft.AspNetCore.App 7.0.0-preview.3.22158.12 [/home/firas/projects/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 7.0.0-preview.3.22151.6 [/home/firas/projects/dotnet/shared/Microsoft.NETCore.App]

[stephentoub]

7.0.0-preview.3.22151.6

Thanks. This maps to https://github.com/dotnet/runtime/commits/2330b4bef645bf8bcd3011f35968e55192c697f5 from March 2nd, which doesn't include #66216 that was merged on March 6th. I'm not sure why the current nightly installer has a two-week old runtime.... @mmitche?