Support for empty struct/union

nimterop/grammar.nim

@@ -183,7 +183,10 @@ proc initGrammar() =
               break
 
     if gStateRT.types.addNewIdentifer(nname):
-      gStateRT.typeStr &= &"  {nname}* {{.importc: \"{prefix}{name}\", header: {gStateRT.currentHeader}, bycopy.}} = object{union}\n"
+      if gStateRT.data.len == 1:
+        gStateRT.typeStr &= &"  {nname}* {{.bycopy.}} = object{union}\n"
+      else:
+        gStateRT.typeStr &= &"  {nname}* {{.importc: \"{prefix}{name}\", header: {gStateRT.currentHeader}, bycopy.}} = object{union}\n"
 
       var
         i = fstart
@@ -273,7 +276,7 @@ proc initGrammar() =
     """
 
     fieldListGrammar = &"""
-      (field_declaration_list
+      (field_declaration_list?
        (field_declaration+
         {typeGrammar}
         (pointer_declarator!

tests/include/test.h

@@ -28,6 +28,8 @@ extern "C" {
 typedef uint8_t PRIMTYPE;
 typedef PRIMTYPE CUSTTYPE;
 
+struct STRUCT0;
+
 struct STRUCT1 {
 	int field1;
 };

tests/tnimterop_c.nim

@@ -29,7 +29,8 @@ var
   pt: PRIMTYPE
   ct: CUSTTYPE
 
-  s: STRUCT1
+  s0: STRUCT0
+  s1: STRUCT1
   s2: STRUCT2
   s3: STRUCT3
   s4: STRUCT4
@@ -52,7 +53,7 @@ var
 pt = 3
 ct = 4
 
-s.field1 = 5
+s1.field1 = 5
 s2.field1 = 6
 s3.field1 = 7
 s4.field2[2] = 5
@@ -80,7 +81,7 @@ i = 5
 check test_call_int() == 5
 check test_call_param(5).field1 == 5
 check test_call_param2(5, s2).field1 == 11
-check test_call_param3(5, s).field1 == 10
+check test_call_param3(5, s1).field1 == 10
 # error: assigning to 'enum ENUM' from incompatible type 'NI' (aka 'long long')
 when defined(cpp):
   discard # TODO