Fix unnecessary hash table creation in cl-prin1 (bug#36566)

cl-prin1 prints all its punctuation by passing strings to prin1.  When
print-circle was set, print_preprocess was creating a new hash table
for each string, causing excessive garbage collection when printing
large Lisp objects with cl-prin1.

* src/print.c (print_number_index): Fix typo in comment above.
(PRINT_CIRCLE_CANDIDATE_P): Don't create print_number_table
for top-level strings with no properties, except when
print_continuous_numbering is on.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/print.c b/src/print.c
index 7c3da68fc98..18330b0fbf4 100644
--- a/src/print.c
+++ b/src/print.c
@@ -81,7 +81,7 @@ static ptrdiff_t print_buffer_pos_byte;
      -N   the object will be printed several times and will take number N.
      N    the object has been printed so we can refer to it as #N#.
    print_number_index holds the largest N already used.
-   N has to be striclty larger than 0 since we need to distinguish -N.  */
+   N has to be strictly larger than 0 since we need to distinguish -N.  */
 static ptrdiff_t print_number_index;
 static void print_interval (INTERVAL interval, Lisp_Object printcharfun);
 
@@ -1149,7 +1149,11 @@ print (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
 }
 
 #define PRINT_CIRCLE_CANDIDATE_P(obj)                      \
-  (STRINGP (obj) || CONSP (obj)                            \
+  ((STRINGP (obj)                                          \
+       && (string_intervals (obj)                          \
+          || print_depth > 1                               \
+          || Vprint_continuous_numbering))                 \
+   || CONSP (obj)                                          \
    || (VECTORLIKEP (obj)                                   \
        && (VECTORP (obj) || COMPILEDP (obj)                \
            || CHAR_TABLE_P (obj) || SUB_CHAR_TABLE_P (obj) \