fix: declare external pou initializers as external (#1290)

Author: mhasel

src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__external_impl_is_not_added_as_external_subroutine.snap

@@ -9,7 +9,7 @@ source_filename = "<internal>"
 %myFb = type {}
 
 @myPrg_instance = external global %myPrg, section "var-$RUSTY$myPrg_instance:r0", !dbg !0
-@__myFb__init = unnamed_addr constant %myFb zeroinitializer, section "var-$RUSTY$__myFb__init:r0", !dbg !5
+@__myFb__init = external global %myFb, section "var-$RUSTY$__myFb__init:r0", !dbg !5
 
 declare i32 @myFunc() section "fn-$RUSTY$myFunc:i32"
 

src/codegen/tests/initialization_test/global_initializers.rs

@@ -153,3 +153,45 @@ fn global_constant_without_initializer_gets_declared_initializer() {
     //should initialize cmd1 and cmd2 with @__comamnds__init
     insta::assert_snapshot!(result);
 }
+
+#[test]
+fn external_pous_get_external_initializers() {
+    let result = codegen(
+        "
+        {external} FUNCTION_BLOCK ext_fb END_FUNCTION_BLOCK
+        {external} PROGRAM ext_prog END_PROGRAM
+        ",
+    );
+
+    insta::assert_snapshot!(result, @r###"
+    ; ModuleID = '<internal>'
+    source_filename = "<internal>"
+
+    %ext_fb = type {}
+    %ext_prog = type {}
+
+    @__ext_fb__init = external global %ext_fb, section "var-$RUSTY$__ext_fb__init:r0"
+    @ext_prog_instance = external global %ext_prog, section "var-$RUSTY$ext_prog_instance:r0"
+
+    declare void @ext_fb(%ext_fb*) section "fn-$RUSTY$ext_fb:v"
+
+    declare void @ext_prog(%ext_prog*) section "fn-$RUSTY$ext_prog:v"
+    "###);
+}
+
+#[test]
+#[ignore = "external struct initializers are not declared external"]
+fn external_aggregate_types_get_external_initializers() {
+    let result = codegen(
+        "
+        {external} 
+        VAR_GLOBAL
+          a: ARRAY[0..10] OF DINT;
+          b: STRING;
+          c: STRUCT a: INT; END_STRUCT
+        END_VAR
+        ",
+    );
+
+    insta::assert_snapshot!(result, @r###""###);
+}

src/index/visitor.rs

@@ -147,7 +147,8 @@ pub fn visit_pou(index: &mut Index, pou: &Pou) {
                 &pou.name,
                 pou.name_location.clone(),
             )
-            .set_constant(true);
+            .set_constant(true)
+            .set_linkage(pou.linkage);
             index.register_global_initializer(&global_struct_name, variable);
             index.register_pou(PouIndexEntry::create_function_block_entry(
                 &pou.name,
@@ -165,7 +166,8 @@ pub fn visit_pou(index: &mut Index, pou: &Pou) {
                 &pou.name,
                 pou.name_location.clone(),
             )
-            .set_constant(true);
+            .set_constant(true)
+            .set_linkage(pou.linkage);
             index.register_global_initializer(&global_struct_name, variable);
             index.register_pou(PouIndexEntry::create_class_entry(
                 &pou.name,