bug#15033: [PATCH] Fix display of symbols containing backslashes

[David Kastrup <dak@gnu.org>]

Symbols printed with `#{...#}' notation need to double backslashes when
displaying as they serve as escape characters when reading.  The
behavior before this patch is clearly erroneous:

GNU Guile 2.0.7
[...]
scheme@(guile-user)> (string->symbol "\\(")
$1 = #{\\x28;}#
scheme@(guile-user)> (symbol->string '#{\\x28;}#)
$2 = "\\x28;"
---
 libguile/print.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libguile/print.c b/libguile/print.c
index 50f5a3e..bb7fd84 100644
--- a/libguile/print.c
+++ b/libguile/print.c
@@ -448,7 +448,8 @@ print_extended_symbol (SCM sym, SCM port)
                                             SUBSEQUENT_IDENTIFIER_MASK
                                             | UC_CATEGORY_MASK_Zs))
         {
-          if (!display_character (c, port, strategy))
+          if (!display_character (c, port, strategy)
+	      || (c == '\\' && !display_character (c, port, strategy)))
             scm_encoding_error ("print_extended_symbol", errno,
                                 "cannot convert to output locale",
                                 port, SCM_MAKE_CHAR (c));
-- 
1.8.1.2