Cannot marshal 'parameter #1': Pointers cannot reference marshaled structures. Use ByRef instead.

[ujos]

Cannot pass the structure via pointer if structure contains a bool variable. Code compiles but MarshalDirectiveException exception is thrown during runtime.

Steps to reproduce

1. Download and extract test.zip
2. Run reproduce.cmd

Expected that test.exe prints nothing.

In fact the output is:

Unhandled Exception: System.Runtime.InteropServices.MarshalDirectiveException: Cannot marshal 'parameter #1': Pointers cannot reference marshaled structures.  Use ByRef instead.
   at TestLib.DLL.foo(X* x)
   at Program.<Main>$(String[] args)

In case if I replace pointer with ref, the code works.

Version

 (master) test $ ClangSharpPInvokeGenerator --version
ClangSharp P/Invoke Binding Generator version 14.0.0
  clang version 14.0.0
  clangsharp version 14.0.0

Archive content

// test_lib.h

#include <stdbool.h>

#ifdef __cplusplus
extern "C"
{
#endif

struct X 
{
    bool Flag;
};

void __declspec(dllexport) foo(struct X const* x);

#ifdef __cplusplus
}
#endif

// test_lib.cpp

#include "test_lib.h"

void foo(X const*)
{
}

Following is config file for ClangSharpPInvokeGenerator

--file
test_lib.h

--namespace
TestLib

--headerFile
pinvoke-header.txt

--output
test_lib.cs

--language
c++

--methodClassName
DLL

--libraryPath
test_lib.dll

--config
compatible-codegen

Following is a C# test program:

using ClangSharp.Interop;

unsafe
{
    var x = new TestLib.X();

    TestLib.DLL.foo(&x);
}

[ujos]

Following is a quote from Blittable and Non-Blittable Types MSDN article:

Most data types have a common representation in both managed and unmanaged memory and do not require special handling by the interop marshaller. These types are called blittable types because they do not require conversion when they are passed between managed and unmanaged code.

Structures that are returned from platform invoke calls must be blittable types. Platform invoke does not support non-blittable structures as return types.

[tannergooding]

At first glance this looks like a bug in ClangSharp. bool on the native side should be normalized to byte on the C# side due to the ABI incompatibility.

For .NET 7 and later, bool could be used if the user opts into [assembly: System.Runtime.CompilerServices.DisableRuntimeMarshalling], but that's not a feature ClangSharp supports yet.

I thought I had tests covering this scenario, but I'll be able to take a look in a day or two and confirm.

[ujos]

It seems you handle the bool type in the function declaration but not in the structure declaration.