Create less garbage to collect while reading symbols.

* src/lread.c (read1): When interning a symbol, only create a new
string object for the name if we're going to use it for a new symbol
object.

1 files changed, 44 insertions, 18 deletions

diff --git a/src/lread.c b/src/lread.c
index d6a7e55b98a..3004e2b1915 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -3442,25 +3442,51 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
             if (! NILP (result))
               return unbind_to (count, result);
           }
+        {
+          Lisp_Object result;
+          ptrdiff_t nbytes = p - read_buffer;
+          ptrdiff_t nchars
+            = (multibyte
+               ? multibyte_chars_in_text ((unsigned char *) read_buffer,
+                                          nbytes)
+               : nbytes);
+
+          if (uninterned_symbol)
+            {
+              Lisp_Object name
+                = ((! NILP (Vpurify_flag)
+                    ? make_pure_string : make_specified_string)
+                   (read_buffer, nchars, nbytes, multibyte));
+              result = Fmake_symbol (name);
+            }
+          else
+            {
+              /* Don't create the string object for the name unless
+                 we're going to retain it in a new symbol.
 
-        ptrdiff_t nbytes = p - read_buffer;
-        ptrdiff_t nchars
-          = (multibyte
-             ? multibyte_chars_in_text ((unsigned char *) read_buffer,
-                                        nbytes)
-             : nbytes);
-        Lisp_Object name = ((uninterned_symbol && ! NILP (Vpurify_flag)
-                             ? make_pure_string : make_specified_string)
-                            (read_buffer, nchars, nbytes, multibyte));
-        Lisp_Object result = (uninterned_symbol ? Fmake_symbol (name)
-                              : Fintern (name, Qnil));
-
-        if (EQ (Vread_with_symbol_positions, Qt)
-            || EQ (Vread_with_symbol_positions, readcharfun))
-          Vread_symbol_positions_list
-            = Fcons (Fcons (result, make_number (start_position)),
-                     Vread_symbol_positions_list);
-        return unbind_to (count, result);
+                 Like intern_1 but supports multibyte names.  */
+              Lisp_Object obarray = check_obarray (Vobarray);
+              Lisp_Object tem = oblookup (obarray, read_buffer,
+                                          nchars, nbytes);
+
+              if (SYMBOLP (tem))
+                result = tem;
+              else
+                {
+                  Lisp_Object name
+                    = make_specified_string (read_buffer, nchars, nbytes,
+                                             multibyte);
+                  result = intern_driver (name, obarray, tem);
+                }
+            }
+
+          if (EQ (Vread_with_symbol_positions, Qt)
+              || EQ (Vread_with_symbol_positions, readcharfun))
+            Vread_symbol_positions_list
+              = Fcons (Fcons (result, make_number (start_position)),
+                       Vread_symbol_positions_list);
+          return unbind_to (count, result);
+        }
       }
     }
 }