Improve encoding error reporting.

* libguile/strings.c (scm_encoding_error): Change arguments to convey
  more information.  Raise the error with `scm_throw ()', passing all
  the information to the handler.
  (scm_from_stringn, scm_to_stringn): Update accordingly.

* test-suite/tests/ports.test ("string ports")["wrong encoding"]: Check
  the arguments passed to the `throw' handler.

* test-suite/tests/r6rs-ports.test ("7.2.11 Binary
  Output")["put-bytevector with wrong-encoding string port"]: Likewise.

libguile/strings.c

@@ -1393,9 +1393,21 @@ scm_is_string (SCM obj)
 
 SCM_SYMBOL (scm_encoding_error_key, "encoding-error");
 static void
-scm_encoding_error (const char *subr, const char *message, SCM args)
+scm_encoding_error (const char *subr, int err, const char *message,
+		    const char *from, const char *to, SCM string_or_bv)
 {
-  scm_error (scm_encoding_error_key, subr, message, args, SCM_BOOL_F);
+  /* Raise an exception that conveys all the information needed to debug the
+     problem.  Only perform locale conversions that are safe; in particular,
+     don't try to display STRING_OR_BV when it's a string since converting it to
+     the output locale may fail.  */
+  scm_throw (scm_encoding_error_key,
+	     scm_list_n (scm_from_locale_string (subr),
+			 scm_from_locale_string (message),
+			 scm_from_int (err),
+			 scm_from_locale_string (from),
+			 scm_from_locale_string (to),
+			 string_or_bv,
+			 SCM_UNDEFINED));
 }
 
 SCM
@@ -1427,23 +1439,20 @@ scm_from_stringn (const char *str, size_t len, const char *encoding,
                                                 NULL,
                                                 NULL, &u32len);
 
-  if (u32 == NULL)
+  if (SCM_UNLIKELY (u32 == NULL))
     {
-      if (errno == ENOMEM)
+      /* Raise an error and pass the raw C string as a bytevector to the `throw'
-        scm_memory_error ("locale string conversion");
+	 handler.  */
-      else
+      SCM bv;
-        {
+      signed char *buf;
-          /* There are invalid sequences in the input string.  */
+
-          SCM errstr;
+      buf = scm_gc_malloc_pointerless (len, "bytevector");
-          char *dst;
+      memcpy (buf, str, len);
-          errstr = scm_i_make_string (len, &dst);
+      bv = scm_c_take_bytevector (buf, len);
-          memcpy (dst, str, len);
+
-          scm_encoding_error (NULL,
+      scm_encoding_error (__func__, errno,
-			      "input locale conversion error from ~s: ~s",
+			  "input locale conversion error",
-			      scm_list_2 (scm_from_locale_string (encoding),
+			  encoding, "UTF-32", bv);
-					  errstr));
-          scm_remember_upto_here_1 (errstr);
-        }
     }
 
   i = 0;
@@ -1759,8 +1768,9 @@ scm_to_stringn (SCM str, size_t *lenp, const char *encoding,
                          &buf, &len);
 
       if (ret != 0)
-        scm_encoding_error (NULL, "cannot convert to output locale ~s: \"~s\"",
+        scm_encoding_error (__func__, errno,
-                            scm_list_2 (scm_from_locale_string (enc), str));
+			    "cannot convert to output locale",
+			    "ISO-8859-1", enc, str);
     }
   else
     {
@@ -1771,8 +1781,9 @@ scm_to_stringn (SCM str, size_t *lenp, const char *encoding,
                                   NULL,
                                   NULL, &len);
       if (buf == NULL)
-        scm_encoding_error (NULL, "cannot convert to output locale ~s: \"~s\"",
+        scm_encoding_error (__func__, errno,
-                            scm_list_2 (scm_from_locale_string (enc), str));
+			    "cannot convert to output locale",
+			    "UTF-32", enc, str);
     }
   if (handler == SCM_FAILED_CONVERSION_ESCAPE_SEQUENCE)
     {

test-suite/tests/ports.test

@@ -335,14 +335,20 @@
                   (lambda ()
                     (display str)))))))
 
-  (pass-if-exception "wrong encoding"
+  (pass-if "wrong encoding"
-    exception:encoding-error
     (let ((str "ĉu bone?"))
+      (catch 'encoding-error
+        (lambda ()
           ;; Latin-1 cannot represent ‘ĉ’.
           (with-fluids ((%default-port-encoding "ISO-8859-1"))
             (with-output-to-string
               (lambda ()
-            (display str)))))))
+                (display str)))))
+        (lambda (key subr message errno from to faulty-str)
+          (and (eq? faulty-str str)
+               (string=? from "UTF-32")
+               (string=? to "ISO-8859-1")
+               (string? (strerror errno))))))))
 
 (with-test-prefix "call-with-output-string"
 

test-suite/tests/r6rs-ports.test

@@ -230,14 +230,19 @@
                   (lambda (port)
                     (put-bytevector port bv)))))))
 
-  (pass-if-exception "put-bytevector with wrong-encoding string port"
+  (pass-if "put-bytevector with wrong-encoding string port"
-    exception:encoding-error
     (let* ((str "hello, world")
            (bv  (string->utf16 str)))
+      (catch 'encoding-error
+        (lambda ()
           (with-fluids ((%default-port-encoding "UTF-32"))
             (call-with-output-string
               (lambda (port)
-            (put-bytevector port bv)))))))
+                (put-bytevector port bv)))))
+        (lambda (key subr message errno from to faulty-bv)
+          (and (bytevector=? faulty-bv bv)
+               (string=? to "UTF-32")
+               (string? (strerror errno))))))))
 
 
 (with-test-prefix "7.2.7 Input Ports"