py: Add mp_obj_new_str_from_vstr, and use it where relevant.

This patch allows to reuse vstr memory when creating str/bytes object.
This improves memory usage.

Also saves code ROM: 128 bytes on stmhal, 92 bytes on bare-arm, and 88
bytes on unix x64.

1 files changed, 4 insertions, 4 deletions

diff --git a/py/objexcept.c b/py/objexcept.c
index e872db341..f2f4012bc 100644
--- a/py/objexcept.c
+++ b/py/objexcept.c
@@ -351,13 +351,13 @@ mp_obj_t mp_obj_new_exception_msg_varg(const mp_obj_type_t *exc_type, const char
         } else {
             // render exception message and store as .args[0]
             // TODO: optimize bufferbloat
-            vstr_t *vstr = vstr_new();
+            vstr_t vstr;
+            vstr_init(&vstr, 16);
             va_list ap;
             va_start(ap, fmt);
-            vstr_vprintf(vstr, fmt, ap);
+            vstr_vprintf(&vstr, fmt, ap);
             va_end(ap);
-            o->args->items[0] = mp_obj_new_str(vstr->buf, vstr->len, false);
-            vstr_free(vstr);
+            o->args->items[0] = mp_obj_new_str_from_vstr(&mp_type_str, &vstr);
         }
     }