Add custom entry point support.

Hosts like ASP.net don't want to call ExecuteAssembly, because their
entry point is library, not a managed exe.  However, forcing cross
platform hosts to actually call CreateAppDomainWithManager and
CreateDelegate themselves requires a bunch of tedious code, since these
hosts don't have access to mscoree.h and the PAL.

This change adds the ability to specificy an assembly, type and method
which can be used as a custom entrypoint.  The signiture of the managed
entry point needs to be `static int E(int, char**)`.

1 files changed, 37 insertions, 4 deletions

diff --git a/src/dlls/mscoree/unixinterface.cpp b/src/dlls/mscoree/unixinterface.cpp
index 169b0aab13..265e99539e 100644
--- a/src/dlls/mscoree/unixinterface.cpp
+++ b/src/dlls/mscoree/unixinterface.cpp
@@ -16,6 +16,11 @@
 #include <utilcode.h>
 #include <corhost.h>
 
+typedef int (STDMETHODCALLTYPE *HostMain)(
+    const int argc,
+    const wchar_t** argv
+    );
+
 #define ASSERTE_ALL_BUILDS(expr) _ASSERTE_ALL_BUILDS(__FILE__, (expr))
 
 // Holder for const wide strings
@@ -94,7 +99,10 @@ static LPCWSTR* StringArrayToUnicode(int argc, LPCSTR* argv)
 //  propertyValues          - Values of properties of the app domain
 //  argc                    - Number of arguments passed to the executed assembly
 //  argv                    - Array of arguments passed to the executed assembly
-//  managedAssemblyPath     - Path of the managed assembly to execute
+//  managedAssemblyPath     - Path of the managed assembly to execute (or NULL if using a custom entrypoint).
+//  enntyPointAssemblyName  - Name of the assembly which holds the custom entry point (or NULL to use managedAssemblyPath).
+//  entryPointTypeName      - Name of the type which holds the custom entry point (or NULL to use managedAssemblyPath).
+//  entryPointMethodName    - Name of the method which is the custom entry point (or NULL to use managedAssemblyPath).
 //  exitCode                - Exit code returned by the executed assembly
 //
 // Returns:
@@ -111,6 +119,9 @@ HRESULT ExecuteAssembly(
             int argc,
             LPCSTR* argv,
             LPCSTR managedAssemblyPath,
+            LPCSTR entryPointAssemblyName,
+            LPCSTR entryPointTypeName,
+            LPCSTR entryPointMethodName,
             DWORD* exitCode)
 {
     *exitCode = 0;
@@ -177,11 +188,33 @@ HRESULT ExecuteAssembly(
     ConstWStringArrayHolder argvW;
     argvW.Set(StringArrayToUnicode(argc, argv), argc);
     
-    ConstWStringHolder managedAssemblyPathW = StringToUnicode(managedAssemblyPath);
+    if (entryPointAssemblyName == NULL || entryPointTypeName == NULL || entryPointMethodName == NULL)
+    {
+        ConstWStringHolder managedAssemblyPathW = StringToUnicode(managedAssemblyPath);
 
-    hr = host->ExecuteAssembly(domainId, managedAssemblyPathW, argc, argvW, exitCode);
-    IfFailRet(hr);
+        hr = host->ExecuteAssembly(domainId, managedAssemblyPathW, argc, argvW, exitCode);
+        IfFailRet(hr);
+    }
+    else
+    {
+        ConstWStringHolder entryPointAssemblyNameW = StringToUnicode(entryPointAssemblyName);
+        ConstWStringHolder entryPointTypeNameW = StringToUnicode(entryPointTypeName);
+        ConstWStringHolder entryPointMethodNameW = StringToUnicode(entryPointMethodName);
+
+        HostMain pHostMain;
+
+        hr = host->CreateDelegate(
+            domainId,
+            entryPointAssemblyNameW,
+            entryPointTypeNameW,
+            entryPointMethodNameW,
+            (INT_PTR*)&pHostMain);
+        
+        IfFailRet(hr);
 
+        *exitCode = pHostMain(argc, argvW);
+    }
+    
     hr = host->UnloadAppDomain(domainId,
                                true); // Wait until done
     IfFailRet(hr);