C#: Replace libnethost dependency to find hostfxr

We want to replace libnethost as it gives us issues with some compilers.
Our implementation tries to mimic libnethost's hostfxr_resolver search
logic. We try to use the same function names for easier comparing in
case we need to update this in the future.

2 files changed, 370 insertions, 0 deletions

diff --git a/modules/mono/thirdparty/coreclr_delegates.h b/modules/mono/thirdparty/coreclr_delegates.h
new file mode 100644
index 0000000000..914ab592df
--- /dev/null
+++ b/modules/mono/thirdparty/coreclr_delegates.h
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#ifndef __CORECLR_DELEGATES_H__
+#define __CORECLR_DELEGATES_H__
+
+#include <stdint.h>
+
+#if defined(_WIN32)
+    #define CORECLR_DELEGATE_CALLTYPE __stdcall
+    #ifdef _WCHAR_T_DEFINED
+        typedef wchar_t char_t;
+    #else
+        typedef unsigned short char_t;
+    #endif
+#else
+    #define CORECLR_DELEGATE_CALLTYPE
+    typedef char char_t;
+#endif
+
+#define UNMANAGEDCALLERSONLY_METHOD ((const char_t*)-1)
+
+// Signature of delegate returned by coreclr_delegate_type::load_assembly_and_get_function_pointer
+typedef int (CORECLR_DELEGATE_CALLTYPE *load_assembly_and_get_function_pointer_fn)(
+    const char_t *assembly_path      /* Fully qualified path to assembly */,
+    const char_t *type_name          /* Assembly qualified type name */,
+    const char_t *method_name        /* Public static method name compatible with delegateType */,
+    const char_t *delegate_type_name /* Assembly qualified delegate type name or null
+                                        or UNMANAGEDCALLERSONLY_METHOD if the method is marked with
+                                        the UnmanagedCallersOnlyAttribute. */,
+    void         *reserved           /* Extensibility parameter (currently unused and must be 0) */,
+    /*out*/ void **delegate          /* Pointer where to store the function pointer result */);
+
+// Signature of delegate returned by load_assembly_and_get_function_pointer_fn when delegate_type_name == null (default)
+typedef int (CORECLR_DELEGATE_CALLTYPE *component_entry_point_fn)(void *arg, int32_t arg_size_in_bytes);
+
+typedef int (CORECLR_DELEGATE_CALLTYPE *get_function_pointer_fn)(
+    const char_t *type_name          /* Assembly qualified type name */,
+    const char_t *method_name        /* Public static method name compatible with delegateType */,
+    const char_t *delegate_type_name /* Assembly qualified delegate type name or null,
+                                        or UNMANAGEDCALLERSONLY_METHOD if the method is marked with
+                                        the UnmanagedCallersOnlyAttribute. */,
+    void         *load_context       /* Extensibility parameter (currently unused and must be 0) */,
+    void         *reserved           /* Extensibility parameter (currently unused and must be 0) */,
+    /*out*/ void **delegate          /* Pointer where to store the function pointer result */);
+
+#endif // __CORECLR_DELEGATES_H__
diff --git a/modules/mono/thirdparty/hostfxr.h b/modules/mono/thirdparty/hostfxr.h
new file mode 100644
index 0000000000..591a8ebbea
--- /dev/null
+++ b/modules/mono/thirdparty/hostfxr.h
@@ -0,0 +1,323 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#ifndef __HOSTFXR_H__
+#define __HOSTFXR_H__
+
+#include <stddef.h>
+#include <stdint.h>
+
+#if defined(_WIN32)
+    #define HOSTFXR_CALLTYPE __cdecl
+    #ifdef _WCHAR_T_DEFINED
+        typedef wchar_t char_t;
+    #else
+        typedef unsigned short char_t;
+    #endif
+#else
+    #define HOSTFXR_CALLTYPE
+    typedef char char_t;
+#endif
+
+enum hostfxr_delegate_type
+{
+    hdt_com_activation,
+    hdt_load_in_memory_assembly,
+    hdt_winrt_activation,
+    hdt_com_register,
+    hdt_com_unregister,
+    hdt_load_assembly_and_get_function_pointer,
+    hdt_get_function_pointer,
+};
+
+typedef int32_t(HOSTFXR_CALLTYPE *hostfxr_main_fn)(const int argc, const char_t **argv);
+typedef int32_t(HOSTFXR_CALLTYPE *hostfxr_main_startupinfo_fn)(
+    const int argc,
+    const char_t **argv,
+    const char_t *host_path,
+    const char_t *dotnet_root,
+    const char_t *app_path);
+typedef int32_t(HOSTFXR_CALLTYPE* hostfxr_main_bundle_startupinfo_fn)(
+    const int argc,
+    const char_t** argv,
+    const char_t* host_path,
+    const char_t* dotnet_root,
+    const char_t* app_path,
+    int64_t bundle_header_offset);
+
+typedef void(HOSTFXR_CALLTYPE *hostfxr_error_writer_fn)(const char_t *message);
+
+//
+// Sets a callback which is to be used to write errors to.
+//
+// Parameters:
+//     error_writer
+//         A callback function which will be invoked every time an error is to be reported.
+//         Or nullptr to unregister previously registered callback and return to the default behavior.
+// Return value:
+//     The previously registered callback (which is now unregistered), or nullptr if no previous callback
+//     was registered
+//
+// The error writer is registered per-thread, so the registration is thread-local. On each thread
+// only one callback can be registered. Subsequent registrations overwrite the previous ones.
+//
+// By default no callback is registered in which case the errors are written to stderr.
+//
+// Each call to the error writer is sort of like writing a single line (the EOL character is omitted).
+// Multiple calls to the error writer may occur for one failure.
+//
+// If the hostfxr invokes functions in hostpolicy as part of its operation, the error writer
+// will be propagated to hostpolicy for the duration of the call. This means that errors from
+// both hostfxr and hostpolicy will be reporter through the same error writer.
+//
+typedef hostfxr_error_writer_fn(HOSTFXR_CALLTYPE *hostfxr_set_error_writer_fn)(hostfxr_error_writer_fn error_writer);
+
+typedef void* hostfxr_handle;
+struct hostfxr_initialize_parameters
+{
+    size_t size;
+    const char_t *host_path;
+    const char_t *dotnet_root;
+};
+
+//
+// Initializes the hosting components for a dotnet command line running an application
+//
+// Parameters:
+//    argc
+//      Number of argv arguments
+//    argv
+//      Command-line arguments for running an application (as if through the dotnet executable).
+//      Only command-line arguments which are accepted by runtime installation are supported, SDK/CLI commands are not supported.
+//      For example 'app.dll app_argument_1 app_argument_2`.
+//    parameters
+//      Optional. Additional parameters for initialization
+//    host_context_handle
+//      On success, this will be populated with an opaque value representing the initialized host context
+//
+// Return value:
+//    Success          - Hosting components were successfully initialized
+//    HostInvalidState - Hosting components are already initialized
+//
+// This function parses the specified command-line arguments to determine the application to run. It will
+// then find the corresponding .runtimeconfig.json and .deps.json with which to resolve frameworks and
+// dependencies and prepare everything needed to load the runtime.
+//
+// This function only supports arguments for running an application. It does not support SDK commands.
+//
+// This function does not load the runtime.
+//
+typedef int32_t(HOSTFXR_CALLTYPE *hostfxr_initialize_for_dotnet_command_line_fn)(
+    int argc,
+    const char_t **argv,
+    const struct hostfxr_initialize_parameters *parameters,
+    /*out*/ hostfxr_handle *host_context_handle);
+
+//
+// Initializes the hosting components using a .runtimeconfig.json file
+//
+// Parameters:
+//    runtime_config_path
+//      Path to the .runtimeconfig.json file
+//    parameters
+//      Optional. Additional parameters for initialization
+//    host_context_handle
+//      On success, this will be populated with an opaque value representing the initialized host context
+//
+// Return value:
+//    Success                            - Hosting components were successfully initialized
+//    Success_HostAlreadyInitialized     - Config is compatible with already initialized hosting components
+//    Success_DifferentRuntimeProperties - Config has runtime properties that differ from already initialized hosting components
+//    CoreHostIncompatibleConfig         - Config is incompatible with already initialized hosting components
+//
+// This function will process the .runtimeconfig.json to resolve frameworks and prepare everything needed
+// to load the runtime. It will only process the .deps.json from frameworks (not any app/component that
+// may be next to the .runtimeconfig.json).
+//
+// This function does not load the runtime.
+//
+// If called when the runtime has already been loaded, this function will check if the specified runtime
+// config is compatible with the existing runtime.
+//
+// Both Success_HostAlreadyInitialized and Success_DifferentRuntimeProperties codes are considered successful
+// initializations. In the case of Success_DifferentRuntimeProperties, it is left to the consumer to verify that
+// the difference in properties is acceptable.
+//
+typedef int32_t(HOSTFXR_CALLTYPE *hostfxr_initialize_for_runtime_config_fn)(
+    const char_t *runtime_config_path,
+    const struct hostfxr_initialize_parameters *parameters,
+    /*out*/ hostfxr_handle *host_context_handle);
+
+//
+// Gets the runtime property value for an initialized host context
+//
+// Parameters:
+//     host_context_handle
+//       Handle to the initialized host context
+//     name
+//       Runtime property name
+//     value
+//       Out parameter. Pointer to a buffer with the property value.
+//
+// Return value:
+//     The error code result.
+//
+// The buffer pointed to by value is owned by the host context. The lifetime of the buffer is only
+// guaranteed until any of the below occur:
+//   - a 'run' method is called for the host context
+//   - properties are changed via hostfxr_set_runtime_property_value
+//   - the host context is closed via 'hostfxr_close'
+//
+// If host_context_handle is nullptr and an active host context exists, this function will get the
+// property value for the active host context.
+//
+typedef int32_t(HOSTFXR_CALLTYPE *hostfxr_get_runtime_property_value_fn)(
+    const hostfxr_handle host_context_handle,
+    const char_t *name,
+    /*out*/ const char_t **value);
+
+//
+// Sets the value of a runtime property for an initialized host context
+//
+// Parameters:
+//     host_context_handle
+//       Handle to the initialized host context
+//     name
+//       Runtime property name
+//     value
+//       Value to set
+//
+// Return value:
+//     The error code result.
+//
+// Setting properties is only supported for the first host context, before the runtime has been loaded.
+//
+// If the property already exists in the host context, it will be overwritten. If value is nullptr, the
+// property will be removed.
+//
+typedef int32_t(HOSTFXR_CALLTYPE *hostfxr_set_runtime_property_value_fn)(
+    const hostfxr_handle host_context_handle,
+    const char_t *name,
+    const char_t *value);
+
+//
+// Gets all the runtime properties for an initialized host context
+//
+// Parameters:
+//     host_context_handle
+//       Handle to the initialized host context
+//     count
+//       [in] Size of the keys and values buffers
+//       [out] Number of properties returned (size of keys/values buffers used). If the input value is too
+//             small or keys/values is nullptr, this is populated with the number of available properties
+//     keys
+//       Array of pointers to buffers with runtime property keys
+//     values
+//       Array of pointers to buffers with runtime property values
+//
+// Return value:
+//     The error code result.
+//
+// The buffers pointed to by keys and values are owned by the host context. The lifetime of the buffers is only
+// guaranteed until any of the below occur:
+//   - a 'run' method is called for the host context
+//   - properties are changed via hostfxr_set_runtime_property_value
+//   - the host context is closed via 'hostfxr_close'
+//
+// If host_context_handle is nullptr and an active host context exists, this function will get the
+// properties for the active host context.
+//
+typedef int32_t(HOSTFXR_CALLTYPE *hostfxr_get_runtime_properties_fn)(
+    const hostfxr_handle host_context_handle,
+    /*inout*/ size_t * count,
+    /*out*/ const char_t **keys,
+    /*out*/ const char_t **values);
+
+//
+// Load CoreCLR and run the application for an initialized host context
+//
+// Parameters:
+//     host_context_handle
+//       Handle to the initialized host context
+//
+// Return value:
+//     If the app was successfully run, the exit code of the application. Otherwise, the error code result.
+//
+// The host_context_handle must have been initialized using hostfxr_initialize_for_dotnet_command_line.
+//
+// This function will not return until the managed application exits.
+//
+typedef int32_t(HOSTFXR_CALLTYPE *hostfxr_run_app_fn)(const hostfxr_handle host_context_handle);
+
+//
+// Gets a typed delegate from the currently loaded CoreCLR or from a newly created one.
+//
+// Parameters:
+//     host_context_handle
+//       Handle to the initialized host context
+//     type
+//       Type of runtime delegate requested
+//     delegate
+//       An out parameter that will be assigned the delegate.
+//
+// Return value:
+//     The error code result.
+//
+// If the host_context_handle was initialized using hostfxr_initialize_for_runtime_config,
+// then all delegate types are supported.
+// If the host_context_handle was initialized using hostfxr_initialize_for_dotnet_command_line,
+// then only the following delegate types are currently supported:
+//     hdt_load_assembly_and_get_function_pointer
+//     hdt_get_function_pointer
+//
+typedef int32_t(HOSTFXR_CALLTYPE *hostfxr_get_runtime_delegate_fn)(
+    const hostfxr_handle host_context_handle,
+    enum hostfxr_delegate_type type,
+    /*out*/ void **delegate);
+
+//
+// Closes an initialized host context
+//
+// Parameters:
+//     host_context_handle
+//       Handle to the initialized host context
+//
+// Return value:
+//     The error code result.
+//
+typedef int32_t(HOSTFXR_CALLTYPE *hostfxr_close_fn)(const hostfxr_handle host_context_handle);
+
+struct hostfxr_dotnet_environment_sdk_info
+{
+    size_t size;
+    const char_t* version;
+    const char_t* path;
+};
+
+typedef void(HOSTFXR_CALLTYPE* hostfxr_get_dotnet_environment_info_result_fn)(
+    const struct hostfxr_dotnet_environment_info* info,
+    void* result_context);
+
+struct hostfxr_dotnet_environment_framework_info
+{
+    size_t size;
+    const char_t* name;
+    const char_t* version;
+    const char_t* path;
+};
+
+struct hostfxr_dotnet_environment_info
+{
+    size_t size;
+
+    const char_t* hostfxr_version;
+    const char_t* hostfxr_commit_hash;
+
+    size_t sdk_count;
+    const struct hostfxr_dotnet_environment_sdk_info* sdks;
+
+    size_t framework_count;
+    const struct hostfxr_dotnet_environment_framework_info* frameworks;
+};
+
+#endif //__HOSTFXR_H__