C API: never return text structures by value

TN: S827-015

langkit/templates/c_api/header_c.mako

@@ -358,8 +358,8 @@ extern ${node_kind_type}
 ${capi.get_name("node_kind")}(${entity_type} *node);
 
 ${c_doc('langkit.kind_name')}
-extern ${text_type}
-${capi.get_name("kind_name")}(${node_kind_type} kind);
+extern void
+${capi.get_name("kind_name")}(${node_kind_type} kind, ${text_type} *result);
 
 ${c_doc('langkit.node_unit')}
 extern int
@@ -375,8 +375,9 @@ extern int
 ${capi.get_name("node_is_synthetic")}(${entity_type} *node);
 
 ${c_doc('langkit.node_short_image')}
-extern ${text_type}
-${capi.get_name("node_short_image")}(${entity_type} *node);
+extern void
+${capi.get_name("node_short_image")}(${entity_type} *node,
+                                     ${text_type} *result);
 
 ${c_doc('langkit.node_text')}
 extern void
@@ -504,8 +505,8 @@ ${capi.get_name('token_is_equivalent')}(${token_type} *left,
                                         ${token_type} *right);
 
 ${c_doc('langkit.entity_image')}
-extern ${text_type}
-${capi.get_name('entity_image')}(${entity_type} ent);
+extern void
+${capi.get_name('entity_image')}(${entity_type} ent, ${text_type} *result);
 
 #ifdef __cplusplus
 }

langkit/templates/c_api/pkg_main_body_ada.mako

@@ -452,8 +452,8 @@ package body ${ada_lib_name}.Implementation.C is
          return ${node_kind_type}'First;
    end;
 
-   function ${capi.get_name("kind_name")}
-     (Kind : ${node_kind_type}) return ${text_type} is
+   procedure ${capi.get_name('kind_name')}
+     (Kind : ${node_kind_type}; Result : access ${text_type}) is
    begin
       Clear_Last_Exception;
 
@@ -461,13 +461,13 @@ package body ${ada_lib_name}.Implementation.C is
          K    : constant ${T.node_kind} := ${T.node_kind}'Enum_Val (Kind);
          Name : Text_Access renames Node_Kind_Names (K);
       begin
-         return (Chars => Name.all'Address, Length => Name'Length,
-                 Is_Allocated => 0);
+         Result.all := (Chars        => Name.all'Address,
+                        Length       => Name'Length,
+                        Is_Allocated => 0);
       end;
    exception
       when Exc : others =>
          Set_Last_Exception (Exc);
-         return (System.Null_Address, 0, Is_Allocated => 0);
    end;
 
    function ${capi.get_name('node_unit')}
@@ -503,19 +503,18 @@ package body ${ada_lib_name}.Implementation.C is
          return 0;
    end;
 
-   function ${capi.get_name('node_short_image')}
-     (Node : ${entity_type}_Ptr) return ${text_type} is
+   procedure ${capi.get_name('node_short_image')}
+     (Node : ${entity_type}_Ptr; Result : access ${text_type}) is
    begin
       Clear_Last_Exception;
       declare
          Img : constant Text_Type := Short_Text_Image (Node.Node);
       begin
-         return Wrap_Alloc (Img);
+         Result.all := Wrap_Alloc (Img);
       end;
    exception
       when Exc : others =>
          Set_Last_Exception (Exc);
-         return (System.Null_Address, 0, 0);
    end;
 
    procedure ${capi.get_name('node_text')}
@@ -835,19 +834,18 @@ package body ${ada_lib_name}.Implementation.C is
          return 0;
    end;
 
-   function ${capi.get_name('entity_image')}
-     (Ent : ${entity_type}_Ptr) return ${text_type} is
+   procedure ${capi.get_name('entity_image')}
+     (Ent : ${entity_type}_Ptr; Result : access ${text_type}) is
    begin
       Clear_Last_Exception;
       declare
          Img : constant Text_Type := Text_Image (Ent.all);
       begin
-         return Wrap_Alloc (Img);
+         Result.all := Wrap_Alloc (Img);
       end;
    exception
       when Exc : others =>
          Set_Last_Exception (Exc);
-         return (System.Null_Address, 0, 0);
    end;
 
    ----------------

langkit/templates/c_api/pkg_main_spec_ada.mako

@@ -393,8 +393,8 @@ private package ${ada_lib_name}.Implementation.C is
            External_name => "${capi.get_name('node_kind')}";
    ${ada_c_doc('langkit.node_kind', 3)}
 
-   function ${capi.get_name('kind_name')} (Kind : ${node_kind_type})
-                                           return ${text_type}
+   procedure ${capi.get_name('kind_name')}
+     (Kind : ${node_kind_type}; Result : access ${text_type})
       with Export        => True,
            Convention    => C,
            External_name => "${capi.get_name('kind_name')}";
@@ -421,8 +421,8 @@ private package ${ada_lib_name}.Implementation.C is
            External_name => "${capi.get_name('node_is_synthetic')}";
    ${ada_c_doc('langkit.node_is_synthetic', 3)}
 
-   function ${capi.get_name('node_short_image')}
-     (Node : ${entity_type}_Ptr) return ${text_type}
+   procedure ${capi.get_name('node_short_image')}
+     (Node : ${entity_type}_Ptr; Result : access ${text_type})
       with Export        => True,
            Convention    => C,
            External_name => "${capi.get_name('node_short_image')}";
@@ -584,8 +584,8 @@ private package ${ada_lib_name}.Implementation.C is
            External_name => "${capi.get_name('token_is_equivalent')}";
    ${ada_c_doc('langkit.token_is_equivalent', 3)}
 
-   function ${capi.get_name('entity_image')}
-     (Ent : ${entity_type}_Ptr) return ${text_type}
+   procedure ${capi.get_name('entity_image')}
+     (Ent : ${entity_type}_Ptr; Result : access ${text_type})
       with Export        => True,
            Convention    => C,
            External_name => "${capi.get_name('entity_image')}";

langkit/templates/ocaml_api/module_ocaml.mako

@@ -536,7 +536,9 @@ module CFunctions = struct
     (ptr ${ocaml_api.c_type(root_entity)} @-> raisable int)
 
   let short_image = foreign ~from:c_lib "${capi.get_name('node_short_image')}"
-    (ptr ${ocaml_api.c_type(root_entity)} @-> raisable Text.c_type)
+    (ptr ${ocaml_api.c_type(root_entity)}
+     @-> ptr Text.c_type
+     @-> raisable void)
 
   let node_sloc_range = foreign ~from:c_lib
     "${capi.get_name('node_sloc_range')}"
@@ -554,7 +556,8 @@ module CFunctions = struct
   let entity_image = foreign ~from:c_lib
     "${capi.get_name('entity_image')}"
     (ptr ${ocaml_api.c_type(root_entity)}
-     @-> raisable Text.c_type)
+     @-> ptr Text.c_type
+     @-> raisable void)
 
   let node_is_token_node = foreign ~from:c_lib
     "${capi.get_name('node_is_token_node')}"
@@ -1018,12 +1021,17 @@ let ${ocaml_api.field_name(field)}
     Token.text_range (token_start node) (token_end node)
 
   let short_image node =
+    let c_result_ptr = allocate_n Text.c_type ~count:1 in
     CFunctions.short_image
       (addr (${ocaml_api.unwrap_value('node', root_entity, 'context node')}))
+      c_result_ptr;
+    !@ c_result_ptr
 
   let entity_image node =
+    let c_result_ptr = allocate_n Text.c_type ~count:1 in
     let node_c_value = ${ocaml_api.unwrap_value('node', root_entity, None)} in
-    CFunctions.entity_image (addr node_c_value)
+    CFunctions.entity_image (addr node_c_value) c_result_ptr;
+    !@ c_result_ptr
 
   let is_token_node node =
     let node_c_value = ${ocaml_api.unwrap_value('node', root_entity, None)} in
@@ -1046,10 +1054,6 @@ let ${ocaml_api.field_name(field)}
       (addr node_c_value) sloc_ptr result_ptr;
     ${ocaml_api.check_for_null('!@ result_ptr', root_entity, '(context node)')}
 
-  let entity_image node =
-    let node_c_value = ${ocaml_api.unwrap_value('node', root_entity, None)} in
-    CFunctions.entity_image (addr node_c_value)
-
   let children_opt node =
     let node_c_value = ${ocaml_api.unwrap_value('node', root_entity, None)} in
     let context = context node in

langkit/templates/python_api/module_py.mako

@@ -1137,9 +1137,10 @@ class ${root_astnode_name}(object):
     @property
     def short_image(self):
         ${py_doc('langkit.node_short_image', 8)}
-        node = self._unwrap(self)
-        text = _node_short_image(ctypes.byref(node))
-        return text._wrap()
+        c_node = self._unwrap(self)
+        c_result = _text()
+        _node_short_image(ctypes.byref(c_node), ctypes.byref(c_result))
+        return c_result._wrap()
 
     def lookup(self, sloc):
         ${py_doc('langkit.lookup_in_node', 8)}
@@ -1343,7 +1344,9 @@ class ${root_astnode_name}(object):
     @property
     def entity_repr(self):
         c_value = self._unwrap(self)
-        return _entity_image(ctypes.byref(c_value))._wrap()
+        c_result = _text()
+        _entity_image(ctypes.byref(c_value), ctypes.byref(c_result))
+        return c_result._wrap()
 
     @property
     def tokens(self):
@@ -1717,7 +1720,7 @@ _node_is_synthetic = _import_func(
 )
 _node_short_image = _import_func(
     '${capi.get_name("node_short_image")}',
-    [ctypes.POINTER(${c_entity})], _text
+    [ctypes.POINTER(${c_entity}), ctypes.POINTER(_text)], None
 )
 _node_text = _import_func(
     '${capi.get_name("node_text")}',
@@ -1796,7 +1799,7 @@ _token_range_text = _import_func(
 % if T.entity.exposed:
 _entity_image = _import_func(
     "${capi.get_name('entity_image')}",
-    [ctypes.POINTER(${c_entity})], _text
+    [ctypes.POINTER(${c_entity}), ctypes.POINTER(_text)], None
 )
 % endif