ref STRUCT* now generated as STRUCT**

[Rans4ckeR]

Actual behavior

It seems I can no longer use several functions (BCryptEnumContexts, BCryptEnumContextFunctions, BCryptResolveProviders) because of invalid signatures.

The DllImport now has an [Optional] attribute and seems to cause the overloads that previously were generated as ref STRUCT* now to be generated as STRUCT**.

Example below for BCryptEnumContexts ppBuffer.

0.2.206-beta generates:

[SupportedOSPlatform("windows6.0.6000")]
internal static unsafe winmdroot.Foundation.NTSTATUS BCryptEnumContexts(winmdroot.Security.Cryptography.BCRYPT_TABLE dwTable, ref uint pcbBuffer, winmdroot.Security.Cryptography.CRYPT_CONTEXTS** ppBuffer)
{
	fixed (uint* pcbBufferLocal = &pcbBuffer)
	{
		winmdroot.Foundation.NTSTATUS __result = PInvoke.BCryptEnumContexts(dwTable, pcbBufferLocal, ppBuffer);
		return __result;
	}
}

[DllImport("bcrypt.dll", ExactSpelling = true)]
[DefaultDllImportSearchPaths(DllImportSearchPath.System32)]
[SupportedOSPlatform("windows6.0.6000")]
internal static extern unsafe winmdroot.Foundation.NTSTATUS BCryptEnumContexts(winmdroot.Security.Cryptography.BCRYPT_TABLE dwTable, uint* pcbBuffer, [Optional] winmdroot.Security.Cryptography.CRYPT_CONTEXTS** ppBuffer);

Expected behavior

0.2.188-beta generates:

[SupportedOSPlatform("windows6.0.6000")]
internal static unsafe winmdroot.Foundation.NTSTATUS BCryptEnumContexts(winmdroot.Security.Cryptography.BCRYPT_TABLE dwTable, ref uint pcbBuffer, ref winmdroot.Security.Cryptography.CRYPT_CONTEXTS* ppBuffer)
{
	fixed (winmdroot.Security.Cryptography.CRYPT_CONTEXTS** ppBufferLocal = &ppBuffer)
	{
		fixed (uint* pcbBufferLocal = &pcbBuffer)
		{
			winmdroot.Foundation.NTSTATUS __result = PInvoke.BCryptEnumContexts(dwTable, pcbBufferLocal, ppBufferLocal);
			return __result;
		}
	}
}

[DllImport("bcrypt.dll", ExactSpelling = true)]
[DefaultDllImportSearchPaths(DllImportSearchPath.System32)]
[SupportedOSPlatform("windows6.0.6000")]
internal static extern unsafe winmdroot.Foundation.NTSTATUS BCryptEnumContexts(winmdroot.Security.Cryptography.BCRYPT_TABLE dwTable, uint* pcbBuffer, winmdroot.Security.Cryptography.CRYPT_CONTEXTS** ppBuffer);

Repro steps

1. NativeMethods.txt content:

BCryptAddContextFunction
BCryptEnumContextFunctions
BCryptEnumContexts
BCryptFreeBuffer
BCryptRemoveContextFunction
BCryptResolveProviders
NCryptOpenStorageProvider
NCryptEnumAlgorithms
NCRYPT_KEY_HANDLE
IGroupPolicyObject
CoInitializeEx
CoCreateInstance
CoUninitialize
RegCreateKeyEx
RegOpenKeyEx
RegDeleteValue
RegSetKeyValue
RegGetValue
CryptEnumOIDInfo
BCRYPT_ECCKEY_BLOB
PCSTR
CRYPT_INTEGER_BLOB
NTE_NO_MORE_ITEMS
szOID_ECC_CURVE_*
CLSID_GroupPolicyObject
NCryptProviderName
BCryptGetProperty
BCryptOpenAlgorithmProvider
BCryptCloseAlgorithmProvider
BCRYPT_ECC_CURVE_NAMES
CryptFindOIDInfo
BCryptGenerateKeyPair
BCryptSetProperty
BCryptDestroyKey
BCRYPT_KEY_LENGTHS_STRUCT
ECC_CURVE_TYPE_ENUM
ECC_CURVE_ALG_ID_ENUM
ALG_CLASS_*
ALG_TYPE_*
ALG_SID_*
CALG_*
CRYPT_*
BCRYPT_*
NCRYPT_*
MS_PRIMITIVE_PROVIDER
MS_PLATFORM_CRYPTO_PROVIDER
GPO_OPEN_*
GPO_SECTION_*
HKEY_*
REG_VALUE_TYPE
SSL_F12_EXTRA_CERT_CHAIN_POLICY_STATUS
CERT_INFO

2. NativeMethods.json content (if present):

3. Any of your own code that should be shared?

Context

• CsWin32 version: 0.2.206-beta
• Win32Metadata version (if explicitly set by project):
• Target Framework: net7.0
• LangVersion: preview

[AArnott]

I'm afraid this is by design, since the ppBuffer is in fact allowed to be NULL and the C# ref syntax doesn't make it intuitive as to how to pass NULL in. All such optional parameters are therefore declared as pointers instead of using ref, in or out.
This shouldn't block any of your scenarios, as far as we're aware. It does unfortunately mean you'll need to update your callers.
One thing you could do is add a partial class to declare your own overload of this method that doesacceptref, and internally obtain its pointer and pass it on to the extern` method. If you have a lot of callers of this method, this will allow you to avoid fixing them all up individually.

[AArnott]

#137 tracks improving usability of this and possibly bringing ref parameters back.