Introduce error context

* include/wordsplit.h (wordsplit) <ws_errctx>: New field.
* src/wordsplit.c (wordsplit_init): Initialize ws_errctx.
(expvar,wordsplit_pathexpand): Save error context.
(wordsplit_clearerr): Free error context.
(wordsplit_perror): Use error context if available.
* tests/wordsplit.at: Reflect changes.

include/wordsplit.h

@@ -110,7 +110,7 @@ struct wordsplit
 			       See ws_getvar for a discussion of possible
 			       return values. */
 
-  const char *ws_input;     /* Input string (the S argument to wordsplit. */
+  const char *ws_input;     /* Input string (the S argument to wordsplit). */
   size_t ws_len;            /* Length of ws_input. */
   size_t ws_endp;           /* Points past the last processed byte in
 			       ws_input. */
@@ -118,6 +118,10 @@ struct wordsplit
   char *ws_usererr;         /* Points to textual description of
 			       the error, if ws_errno is WRDSE_USERERR.  Must
 			       be allocated with malloc(3). */
+  char *ws_errctx;          /* Context in which the error occurred:
+			       For WRDSE_UNDEF - name of the undefined variable,
+			       For WRDSE_GLOBERR - pattern that caused error.
+			    */
   struct wordsplit_node *ws_head, *ws_tail;
 			    /* Doubly-linked list of parsed out nodes. */
   char ws_sep[2];           /* Temporary storage used during splitting */

src/wordsplit.c

@@ -107,6 +107,30 @@ _wsplt_nomem (struct wordsplit *wsp)
   return wsp->ws_errno;
 }
 
+static void
+_wsplt_store_errctx (struct wordsplit *wsp, char const *str, size_t len)
+{
+  free (wsp->ws_errctx);
+  wsp->ws_errctx = malloc (len + 1);
+  if (!wsp->ws_errctx)
+    {
+      wsp->ws_error ("%s",
+		     _("memory exhausted while trying to store error subject"));
+    }
+  else
+    {
+      memcpy (wsp->ws_errctx, str, len);
+      wsp->ws_errctx[len] = 0;
+    }
+}
+
+static inline int
+_wsplt_setctxerr (struct wordsplit *wsp, int ec, char const *str, size_t len)
+{
+  _wsplt_store_errctx (wsp, str, len);
+  return _wsplt_seterr (wsp, ec);
+}
+
 static int wordsplit_run (const char *command, size_t length,
 			  struct wordsplit *wsp,
 			  int flags, int lvl);
@@ -307,6 +331,8 @@ wordsplit_init (struct wordsplit *wsp, const char *input, size_t len,
     wordsplit_free_nodes (wsp);
   wsp->ws_head = wsp->ws_tail = NULL;
 
+  wsp->ws_errctx = NULL;
+
   wordsplit_init0 (wsp);
 
   return 0;
@@ -1575,7 +1601,7 @@ expvar (struct wordsplit *wsp, const char *str, size_t len,
 	}
       else if (wsp->ws_flags & WRDSF_UNDEF)
 	{
-	  _wsplt_seterr (wsp, WRDSE_UNDEF);
+	  _wsplt_setctxerr (wsp, WRDSE_UNDEF, str, *pend - str + 1);
 	  return 1;
 	}
       else
@@ -1680,7 +1706,7 @@ expvar (struct wordsplit *wsp, const char *str, size_t len,
 static int
 begin_var_p (int c)
 {
-  return memchr("{#@*", c, 4) != NULL || ISVARBEG (c) || ISDIGIT (c);
+  return memchr ("{#@*", c, 4) != NULL || ISVARBEG (c) || ISDIGIT (c);
 }
 
 static int
@@ -2098,7 +2124,7 @@ wordsplit_pathexpand (struct wordsplit *wsp)
 
 	    default:
 	      free (pattern);
-	      return _wsplt_seterr (wsp, WRDSE_GLOBERR);
+	      return _wsplt_setctxerr (wsp, WRDSE_GLOBERR, pattern, slen);
 	    }
 
 	  prev = p;
@@ -2754,12 +2780,17 @@ wordsplit_clearerr (struct wordsplit *ws)
   if (ws->ws_errno == WRDSE_USERERR)
     free (ws->ws_usererr);
   ws->ws_usererr = NULL;
+
+  free (ws->ws_errctx);
+  ws->ws_errctx = NULL;
+
   ws->ws_errno = WRDSE_OK;
 }
 
 void
 wordsplit_free (struct wordsplit *ws)
 {
+  wordsplit_clearerr (ws);
   wordsplit_free_nodes (ws);
   wordsplit_free_words (ws);
   free (ws->ws_wordv);
@@ -2823,6 +2854,9 @@ wordsplit_perror (struct wordsplit *wsp)
       break;
 
     default:
-      wsp->ws_error ("%s", wordsplit_strerror (wsp));
+      if (wsp->ws_errctx)
+	wsp->ws_error ("%s: %s", wordsplit_strerror (wsp), wsp->ws_errctx);
+      else
+	wsp->ws_error ("%s", wordsplit_strerror (wsp));
     }
 }

tests/wordsplit.at

@@ -238,7 +238,7 @@ TOTAL: 0
 TESTWSP([bail out on undefined variables],[],[-undef],
 [$FOO],
 [],
-[undefined variable
+[undefined variable: FOO
 ],
 [unset FOO;])