Add support for embedding runtime configuration (#6103)

Runtime configuration (e.g. whether to use server GC) can currently be provided either through environment variables at runtime, or through a RhConfig.ini file placed next to the executable. This adds another channel where we burn a blob similar to RhConfig.ini format into the executable. The order of precedence is environment variable > RhConfig.ini > embedded config.

The `ServerGarbageCollection` project property that is used to determine whether to link with a runtime that supports server GC will be also used to control whether to generate a configuration that enables server GC at runtime by default.

Fixes #6100.

1 files changed, 42 insertions, 23 deletions

diff --git a/src/ILCompiler.CppCodeGen/src/CppCodeGen/CppWriter.cs b/src/ILCompiler.CppCodeGen/src/CppCodeGen/CppWriter.cs
index 78b2b1468..7472c0893 100644
--- a/src/ILCompiler.CppCodeGen/src/CppCodeGen/CppWriter.cs
+++ b/src/ILCompiler.CppCodeGen/src/CppCodeGen/CppWriter.cs
@@ -799,42 +799,61 @@ namespace ILCompiler.CppCodeGen
                     }
                 }
             }
+
+            bool generateMethod = !(node is BlobNode);
+
             string pointerType = node is EETypeNode ? "MethodTable * " : "void* ";
-            nodeCode.Append(pointerType);
-            if (node is EETypeNode)
+            if (generateMethod)
             {
-                nodeCode.Append(GetCppMethodDeclarationName((node as EETypeNode).Type, "__getMethodTable"));
+                nodeCode.Append(pointerType);
+                if (node is EETypeNode)
+                {
+                    nodeCode.Append(GetCppMethodDeclarationName((node as EETypeNode).Type, "__getMethodTable"));
+                }
+                else
+                {
+                    string mangledName = ((ISymbolNode)node).GetMangledName(factory.NameMangler);
+
+                    // Rename generic composition and optional fields nodes to avoid name clash with types
+                    bool shouldReplaceNamespaceQualifier = node is GenericCompositionNode || node is EETypeOptionalFieldsNode;
+                    nodeCode.Append(shouldReplaceNamespaceQualifier ? mangledName.Replace("::", "_") : mangledName);
+                }
+                nodeCode.Append("()");
+                nodeCode.AppendLine();
+                nodeCode.Append("{");
+                nodeCode.Indent();
+                nodeCode.AppendLine();
+                nodeCode.Append("static ");
             }
             else
             {
-                string mangledName = ((ISymbolNode)node).GetMangledName(factory.NameMangler);
-
-                // Rename generic composition and optional fields nodes to avoid name clash with types
-                bool shouldReplaceNamespaceQualifier = node is GenericCompositionNode || node is EETypeOptionalFieldsNode;
-                nodeCode.Append(shouldReplaceNamespaceQualifier ? mangledName.Replace("::", "_") : mangledName);
+                nodeCode.Append("extern \"C\" ");
             }
-            nodeCode.Append("()");
-            nodeCode.AppendLine();
-            nodeCode.Append("{");
-            nodeCode.Indent();
-            nodeCode.AppendLine();
-            nodeCode.Append("static struct {");
+            nodeCode.Append("struct {");
 
             nodeCode.AppendLine();
             nodeCode.Append(GetCodeForNodeStruct(nodeDataSections, node));
 
             nodeCode.AppendLine();
-            nodeCode.Append("} mt = {");
+
+            if (generateMethod)
+                nodeCode.Append("} mt = {");
+            else
+                nodeCode.Append(" } " + ((ISymbolNode)node).GetMangledName(factory.NameMangler) + " = {");
             nodeCode.Append(GetCodeForNodeData(nodeDataSections, relocs, nodeData.Data, node, offset, factory));
 
             nodeCode.Append("};");
-            nodeCode.AppendLine();
-            nodeCode.Append("return ( ");
-            nodeCode.Append(pointerType);
-            nodeCode.Append(")&mt;");
-            nodeCode.Exdent();
-            nodeCode.AppendLine();
-            nodeCode.Append("}");
+
+            if (generateMethod)
+            {
+                nodeCode.AppendLine();
+                nodeCode.Append("return ( ");
+                nodeCode.Append(pointerType);
+                nodeCode.Append(")&mt;");
+                nodeCode.Exdent();
+                nodeCode.AppendLine();
+                nodeCode.Append("}");
+            }
             nodeCode.AppendLine();
             return nodeCode.ToString();
         }
@@ -1018,7 +1037,7 @@ namespace ILCompiler.CppCodeGen
             {
                 if (node is EETypeNode)
                     OutputTypeNode(node as EETypeNode, factory, typeDefinitions, methodTables);
-                else if ((node is EETypeOptionalFieldsNode || node is TypeManagerIndirectionNode || node is GenericCompositionNode) && !(node as ObjectNode).ShouldSkipEmittingObjectNode(factory))
+                else if ((node is EETypeOptionalFieldsNode || node is TypeManagerIndirectionNode || node is GenericCompositionNode || node is BlobNode) && !(node as ObjectNode).ShouldSkipEmittingObjectNode(factory))
                     additionalNodes.Append(GetCodeForObjectNode(node as ObjectNode, factory));
                 else if (node is ArrayOfEmbeddedPointersNode<InterfaceDispatchMapNode> dispatchMap)
                 {