c_str: don't allow symbols.

On 2009-10-02, prior to TXR 014, I made a change to the c_str
function to allow symbolic arguments, so that c_str(sym) could
be used in the code base instead of c_str(symbol_name(sym)).
This was a bad idea, and is allowing numerous functions that
operate on strings to accept symbols also. That behavior is
not documented and not consistently supported. Ironically, I
completely forgot about this and have been consistently using
symbol_name(sym) anyway.  Let us remove this.
Compat support is required because this will break user code
that accidentally depends on this undocumented behavior.

* lib.c (c_str): If the object is type SYM, only return the
symbol_name if compatibility with 231 or older is requested,
otherwise fall through to the error case.

* match.c (dump_var): Fix one case where a symbol is passed
directly to put_string. This fails one of the test cases.
More testing is required to see if any other such cases occur.

* txr.1: New entry in the compatibility notes.

1 files changed, 1 insertions, 1 deletions

diff --git a/match.c b/match.c
index 7ff1b27f..18b3fd20 100644
--- a/match.c
+++ b/match.c
@@ -170,7 +170,7 @@ static void dump_var(val var, char *pfx1, size_t len1,
     pprint(value, ss);
     str = get_string_from_stream(ss);
 
-    put_string(var, std_output);
+    put_string(symbol_name(var), std_output);
     dump_byte_string(pfx1);
     dump_byte_string(pfx2);
     put_char(chr('='), std_output);