[CM] [PATCH] Fix R7RS newline escaping in string serialization

[Jinser Kafka]

In R7RS mode, newlines in strings should be escaped as \n to ensure
proper serialization and readback compatibility. This change:

- Makes slashify_table escape newlines when WITH_R7RS is defined
- Adds newline case to slashify_string_to_port for proper \n output

This fixes issues where strings containing newlines would not serialize
correctly in R7RS mode, breaking the round-trip property of write/read.
---
 s7.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/s7.c b/s7.c
index 273f6d1..4534a01 100644
--- a/s7.c
+++ b/s7.c
@@ -15584,7 +15584,12 @@ static void init_ctables(void)
   /* for (int32_t i = 127; i < 160; i++) slashify_table[i] = true; */ /* 6-Apr-24 for utf-8, but this has no effect on s7test?? */
   slashify_table[(uint8_t)'\\'] = true;
   slashify_table[(uint8_t)'"'] = true;
+#if WITH_R7RS
+  /* In R7RS mode, newlines should be escaped to ensure proper serialization */
+  slashify_table[(uint8_t)'\n'] = true;
+#else
   slashify_table[(uint8_t)'\n'] = false;
+#endif
 
   for (int32_t i = 0; i < CTABLE_SIZE; i++)
     symbol_slashify_table[i] = ((slashify_table[i]) || (!char_ok_in_a_name[i])); /* force use of (symbol ...) for cases like '(ab) as symbol */
@@ -33935,6 +33940,7 @@ static void slashify_string_to_port(s7_scheme *sc, s7_pointer port, const char *
 	  case '\'':  port_write_character(port)(sc, '\'', port);  break;
 	  case '\t':  port_write_character(port)(sc, 't', port);   break;
 	  case '\r':  port_write_character(port)(sc, 'r', port);   break;
+	  case '\n':  port_write_character(port)(sc, 'n', port);   break;
 	  case '\b':  port_write_character(port)(sc, 'b', port);   break;
 	  case '\f':  port_write_character(port)(sc, 'f', port);   break;
 	  case '\?':  port_write_character(port)(sc, '?', port);   break;
-- 
2.51.0