crystal_linkage.patch

diff --git a/src/compiler/crystal/codegen/ast.cr b/src/compiler/crystal/codegen/ast.cr
index ab4fa76d4..ed3465be1 100644
--- a/src/compiler/crystal/codegen/ast.cr
+++ b/src/compiler/crystal/codegen/ast.cr
@@ -72,6 +72,10 @@ module Crystal
       nil
     end
 
+    def linkage
+      nil
+    end
+
     @c_calling_convention : Bool? = nil
     property c_calling_convention
 
diff --git a/src/compiler/crystal/codegen/codegen.cr b/src/compiler/crystal/codegen/codegen.cr
index 7e15b1bdc..e4d05ba4a 100644
--- a/src/compiler/crystal/codegen/codegen.cr
+++ b/src/compiler/crystal/codegen/codegen.cr
@@ -283,6 +283,7 @@ module Crystal
       ret_type = @llvm_typer.llvm_return_type(@main_ret_type)
       main_type = LLVM::Type.function([llvm_context.int32, llvm_context.void_pointer.pointer], ret_type)
       @main = @llvm_mod.functions.add(MAIN_NAME, main_type)
+      @main.linkage = LLVM::Linkage::Internal if @single_module
       @fun_types = { {@llvm_mod, MAIN_NAME} => main_type }
 
       if @program.has_flag?("msvc")
diff --git a/src/compiler/crystal/codegen/fun.cr b/src/compiler/crystal/codegen/fun.cr
index c56bde6e5..69467027d 100644
--- a/src/compiler/crystal/codegen/fun.cr
+++ b/src/compiler/crystal/codegen/fun.cr
@@ -337,7 +337,7 @@ class Crystal::CodeGenVisitor
       end
     end
 
-    if @single_module && !target_def.no_inline? && !target_def.is_a?(External)
+    if @single_module && !target_def.is_a?(External)
       context.fun.linkage = LLVM::Linkage::Internal
     end
 
@@ -395,6 +395,10 @@ class Crystal::CodeGenVisitor
       context.fun.call_convention = call_convention
     end
 
+    if @single_module && (linkage = target_def.linkage)
+      context.fun.linkage = linkage
+    end
+
     i = 0
     args.each do |arg|
       param = context.fun.params[i + offset]
@@ -448,11 +452,7 @@ class Crystal::CodeGenVisitor
     context.fun.add_attribute LLVM::Attribute::ReturnsTwice if target_def.returns_twice?
     context.fun.add_attribute LLVM::Attribute::Naked if target_def.naked?
     context.fun.add_attribute LLVM::Attribute::NoReturn if target_def.no_returns?
-
-    if target_def.no_inline?
-      context.fun.add_attribute LLVM::Attribute::NoInline
-      context.fun.linkage = LLVM::Linkage::External
-    end
+    context.fun.add_attribute LLVM::Attribute::NoInline if target_def.no_inline?
   end
 
   def setup_closure_vars(def_vars, closure_vars, context, closure_type, closure_ptr)
diff --git a/src/compiler/crystal/program.cr b/src/compiler/crystal/program.cr
index 840afd2b6..699da7fe4 100644
--- a/src/compiler/crystal/program.cr
+++ b/src/compiler/crystal/program.cr
@@ -239,6 +239,7 @@ module Crystal
       types["Extern"] = @extern_annotation = AnnotationType.new self, self, "Extern"
       types["Flags"] = @flags_annotation = AnnotationType.new self, self, "Flags"
       types["Link"] = @link_annotation = AnnotationType.new self, self, "Link"
+      types["Linkage"] = @linkage_annotation = AnnotationType.new self, self, "Linkage"
       types["Naked"] = @naked_annotation = AnnotationType.new self, self, "Naked"
       types["NoInline"] = @no_inline_annotation = AnnotationType.new self, self, "NoInline"
       types["Packed"] = @packed_annotation = AnnotationType.new self, self, "Packed"
@@ -534,7 +535,8 @@ module Crystal
                      packed_annotation thread_local_annotation no_inline_annotation
                      always_inline_annotation naked_annotation returns_twice_annotation
                      raises_annotation primitive_annotation call_convention_annotation
-                     flags_annotation link_annotation extern_annotation deprecated_annotation experimental_annotation) %}
+                     flags_annotation link_annotation linkage_annotation extern_annotation
+                     deprecated_annotation experimental_annotation) %}
       def {{name.id}}
         @{{name.id}}.not_nil!
       end
diff --git a/src/compiler/crystal/semantic/ast.cr b/src/compiler/crystal/semantic/ast.cr
index f4fa683ef..b2849fbef 100644
--- a/src/compiler/crystal/semantic/ast.cr
+++ b/src/compiler/crystal/semantic/ast.cr
@@ -689,6 +689,7 @@ module Crystal
     property real_name : String
     property! fun_def : FunDef
     property call_convention : LLVM::CallConvention?
+    property linkage : LLVM::Linkage?
     property wasm_import_module : String?
 
     property? dead = false
diff --git a/src/compiler/crystal/semantic/top_level_visitor.cr b/src/compiler/crystal/semantic/top_level_visitor.cr
index cfc8dddc8..8c93c52a9 100644
--- a/src/compiler/crystal/semantic/top_level_visitor.cr
+++ b/src/compiler/crystal/semantic/top_level_visitor.cr
@@ -528,6 +528,24 @@ class Crystal::TopLevelVisitor < Crystal::SemanticVisitor
     node.body = primitive
   end
 
+  private def process_def_linkage_annotation(node, ann)
+    if ann.args.size != 1
+      ann.wrong_number_of_arguments "annotation Linkage", ann.args.size, 1
+    end
+
+    arg = ann.args.first
+    unless arg.is_a?(StringLiteral)
+      arg.raise "argument to Linkage must be a string"
+    end
+
+    value = LLVM::Linkage.parse?(arg.value)
+    unless value
+      arg.raise "invalid linkage. Valid values are #{LLVM::Linkage.values.join ", "}"
+    end
+
+    node.linkage = value
+  end
+
   def visit(node : Include)
     check_outside_exp node, "include"
     include_in current_type, node, :included
@@ -984,8 +1002,10 @@ class Crystal::TopLevelVisitor < Crystal::SemanticVisitor
         call_convention = parse_call_convention(ann, call_convention)
       elsif annotation_type == @program.primitive_annotation
         process_def_primitive_annotation(external, ann)
+      elsif annotation_type == @program.linkage_annotation
+        process_def_linkage_annotation(external, ann)
       else
-        ann.raise "funs can only be annotated with: NoInline, AlwaysInline, Naked, ReturnsTwice, Raises, CallConvention"
+        ann.raise "funs can only be annotated with: NoInline, AlwaysInline, Naked, ReturnsTwice, Raises, CallConvention or Linkage"
       end
     end