Properly initialize the char array used in type hash calculations. (r…

…os2#1182) (ros2#1184)

Previously, we were zero initializing it and only setting
up one of its fields.  But that doesn't totally properly
initialize it; we really should call rcutils_char_array_init
to make sure everything is initialized.  Do that in the
live source, as well as in the test for it.

Signed-off-by: Chris Lalancette <clalancette@gmail.com>
(cherry picked from commit bfe00f7)

Co-authored-by: Chris Lalancette <clalancette@gmail.com>

rcl/src/rcl/type_hash.c

@@ -23,6 +23,8 @@
 #include "rcutils/sha256.h"
 #include "type_description_interfaces/msg/type_description.h"
 
+#include "./common.h"
+
 static int yaml_write_handler(void * ext, uint8_t * buffer, size_t size)
 {
   rcutils_char_array_t * repr = (rcutils_char_array_t *)ext;
@@ -249,8 +251,13 @@ rcl_calculate_type_hash(
   RCL_CHECK_ARGUMENT_FOR_NULL(output_hash, RCL_RET_INVALID_ARGUMENT);
 
   rcl_ret_t result = RCL_RET_OK;
+  rcl_allocator_t allocator = rcl_get_default_allocator();
   rcutils_char_array_t msg_repr = rcutils_get_zero_initialized_char_array();
-  msg_repr.allocator = rcl_get_default_allocator();
+  rcutils_ret_t rcutils_result = rcutils_char_array_init(&msg_repr, 0, &allocator);
+  if (rcutils_result != RCL_RET_OK) {
+    // rcutils_char_array_init already set the error
+    return rcl_convert_rcutils_ret_to_rcl_ret(rcutils_result);
+  }
 
   output_hash->version = 1;
   result = rcl_type_description_to_hashable_json(type_description, &msg_repr);

rcl/test/rcl/test_type_hash.cpp

@@ -84,7 +84,9 @@ TEST(TestTypeVersionHash, field_type_from_install) {
   {
     rcutils_sha256_ctx_t sha;
     rcutils_char_array_t msg_repr = rcutils_get_zero_initialized_char_array();
-    msg_repr.allocator = rcl_get_default_allocator();
+    rcl_allocator_t allocator = rcl_get_default_allocator();
+    rcutils_ret_t rcutils_result = rcutils_char_array_init(&msg_repr, 0, &allocator);
+    ASSERT_EQ(rcutils_result, RCL_RET_OK);
 
     res = rcl_type_description_to_hashable_json(td_msg, &msg_repr);
     ASSERT_EQ(res, RCL_RET_OK);
@@ -204,7 +206,9 @@ TEST(TestTypeVersionHash, nested_real_type) {
   {
     rcutils_sha256_ctx_t sha;
     rcutils_char_array_t msg_repr = rcutils_get_zero_initialized_char_array();
-    msg_repr.allocator = rcl_get_default_allocator();
+    rcl_allocator_t allocator = rcl_get_default_allocator();
+    rcutils_ret_t rcutils_result = rcutils_char_array_init(&msg_repr, 0, &allocator);
+    ASSERT_EQ(rcutils_result, RCL_RET_OK);
 
     res = rcl_type_description_to_hashable_json(td_msg, &msg_repr);
     ASSERT_EQ(res, RCL_RET_OK);