CODEWITHSUNDEEP
c#access-violation
Justine Krejcha
Justine Krejcha

Reputation: 2176

How can I resolve an access violation in managed C# code with structs?

Problem: When I attempt to access a derived property of a C# struct, it results in an access violation error and the application exits abruptly (with status 0xC0000005). Unlike this question, it happens deterministically on a single property.

The struct definition is in a different library however I control both the client application and the library where the struct is defined.

There is no unmanaged code that I've written for this project. I'm using .NET 5 in both the client application and the library.

Things I've Tried:

  1. Changing the output to x64 in the library didn't help (the application output is x64)
  2. Enabling native code debugging (no information was provided)

MCVE:

Definition

public struct Foo
{
    public const Double BarDivisor = 100.0;

    // ...other properties...

    public Int64 BarWholePart { get; }
    public Int64 BarFractionalPart { get; }
    public Double Bar => Bar + (BarFractionalPart / BarDivisor);
    
    public Foo(Int64 wholePart, Int64 fractionalPart, /* ... */)
    {
        // ...
        BarWholePart = wholePart;
        BarFractionalPart = fractionalPart;
    }

    public static Foo Parse(Int64 whole, Int64 fractional)
    {
        return new Foo(whole, fractional);
         // ...
    }
}

Example of calling code

public void Baz(Foo bar)
{
    // ...
    Double foobar = bar.Bar; // this line results in a crash of the application
    // ...
}

Exception Messages:

Exception thrown at 0x00007FF8C85A21A0 (coreclr.dll) in [application name removed]: 0xC0000005: Access violation writing location 0x000000E70B180FF8.

The Common Language Runtime cannot stop at this exception. Common causes include: incorrect COM interop marshalling and memory corruption. To investigate further use native-only debugging.

Unhandled exception at 0x00007FF8C85A21A0 (coreclr.dll) in [application name removed]: 0xC0000005: Access violation writing location 0x000000E70B180FF8.

The Common Language Runtime cannot stop at this exception. Common causes include: incorrect COM interop marshalling and memory corruption. To investigate further use native-only debugging.

Upvotes: 2

Views: 2331

Answers (1)

Justine Krejcha
Justine Krejcha

Reputation: 2176

This is caused because of a typographical error here

public Double Bar => Bar + (BarFractionalPart / BarDivisor);

BarWholePart should be used instead of Bar. This causes a StackOverflowException, but can sometimes cause an AccessViolationException in the debugger.

Upvotes: 4

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