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[libvirt] [PATCH] Improved error messages in XM conf module



The attached patch improves error handling in the XM config file
parser (src/conf.c).

Currently it has a custom error function called virConfError which has
three problems.  Firstly the conf argument is ignored and therefore
pointless to even pass.  Secondly the function takes a line number
parameter (for reporting the line number where parsing failed), but
this is swallowed and not printed in error messages.  Thirdly, and
most importantly, the name of the file where the error occurs is not
printed by default unless the caller happens to print it.

If there is an _empty_ file in /etc/xen we get this error:

  # virsh list --all
  libvir: error : failed to read configuration file /etc/xen/foobar

but if the spurious file under /etc/xen is non-empty, like a script,
you get completely anonymous errors such as:

  libvir: error : configuration file syntax error: expecting an assignment

or:

  libvir: error : configuration file syntax error: expecting a value

The patch fixes this by printing out the filename and line number if
these are available from the parser context (and the parser context is
passed to virConfError instead of the unused virConfPtr).  With this
patch you'll get errors for the second case like this:

  # virsh list --inactive
  libvir: error : /etc/xen/foobar:1: expecting a value

Rich.

-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://et.redhat.com/~rjones/virt-df/
Index: src/conf.c
===================================================================
RCS file: /data/cvs/libvirt/src/conf.c,v
retrieving revision 1.30
diff -u -r1.30 conf.c
--- src/conf.c	6 Jun 2008 11:09:57 -0000	1.30
+++ src/conf.c	15 Sep 2008 14:57:38 -0000
@@ -79,25 +79,34 @@
 
 /**
  * virConfError:
- * @conf: the configuration if available
+ * @ctxt: the parser context if available or NULL
  * @error: the error number
  * @info: extra information string
- * @line: line for the error
  *
  * Handle an error at the xend daemon interface
  */
 static void
-virConfError(virConfPtr conf ATTRIBUTE_UNUSED,
-             virErrorNumber error, const char *info, int line)
+virConfError(virConfParserCtxtPtr ctxt,
+             virErrorNumber error, const char *info)
 {
-    const char *errmsg;
+    const char *format;
 
     if (error == VIR_ERR_OK)
         return;
 
-    errmsg = __virErrorMsg(error, info);
-    __virRaiseError(NULL, NULL, NULL, VIR_FROM_CONF, error, VIR_ERR_ERROR,
-                    errmsg, info, NULL, line, 0, errmsg, info, line);
+    /* Construct the string 'filename:line: info' if we have that. */
+    if (ctxt && ctxt->filename) {
+        __virRaiseError(NULL, NULL, NULL, VIR_FROM_CONF, error, VIR_ERR_ERROR,
+                        info, ctxt->filename, NULL,
+                        ctxt->line, 0,
+                        "%s:%d: %s", ctxt->filename, ctxt->line, info);
+    } else {
+        format = __virErrorMsg(error, info);
+        __virRaiseError(NULL, NULL, NULL, VIR_FROM_CONF, error, VIR_ERR_ERROR,
+                        info, NULL, NULL,
+                        ctxt ? ctxt->line : 0, 0,
+                        format, info);
+    }
 }
 
 
@@ -152,7 +161,7 @@
     virConfPtr ret;
 
     if (VIR_ALLOC(ret) < 0) {
-        virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocating configuration"), 0);
+        virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocating configuration"));
         return(NULL);
     }
     ret->filename = NULL;
@@ -200,7 +209,7 @@
         return(NULL);
 
     if (VIR_ALLOC(ret) < 0) {
-        virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocating configuration"), 0);
+        virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocating configuration"));
         return(NULL);
     }
 
@@ -335,8 +344,7 @@
         NEXT;
     }
     if ((ctxt->cur >= ctxt->end) || (!c_isdigit(CUR))) {
-        virConfError(NULL, VIR_ERR_CONF_SYNTAX, _("unterminated number"),
-                     ctxt->line);
+        virConfError(ctxt, VIR_ERR_CONF_SYNTAX, _("unterminated number"));
         return(-1);
     }
     while ((ctxt->cur < ctxt->end) && (c_isdigit(CUR))) {
@@ -369,8 +377,7 @@
         while ((ctxt->cur < ctxt->end) && (CUR != '\'') && (!IS_EOL(CUR)))
             NEXT;
         if (CUR != '\'') {
-            virConfError(NULL, VIR_ERR_CONF_SYNTAX, _("unterminated string"),
-                         ctxt->line);
+            virConfError(ctxt, VIR_ERR_CONF_SYNTAX, _("unterminated string"));
             return(NULL);
         }
         ret = strndup(base, ctxt->cur - base);
@@ -386,8 +393,7 @@
         }
         if ((ctxt->cur[0] != '"') || (ctxt->cur[1] != '"') ||
             (ctxt->cur[2] != '"')) {
-            virConfError(NULL, VIR_ERR_CONF_SYNTAX, _("unterminated string"),
-                         ctxt->line);
+            virConfError(ctxt, VIR_ERR_CONF_SYNTAX, _("unterminated string"));
             return(NULL);
         }
         ret = strndup(base, ctxt->cur - base);
@@ -398,8 +404,7 @@
         while ((ctxt->cur < ctxt->end) && (CUR != '"') && (!IS_EOL(CUR)))
             NEXT;
         if (CUR != '"') {
-            virConfError(NULL, VIR_ERR_CONF_SYNTAX, _("unterminated string"),
-                         ctxt->line);
+            virConfError(ctxt, VIR_ERR_CONF_SYNTAX, _("unterminated string"));
             return(NULL);
         }
         ret = strndup(base, ctxt->cur - base);
@@ -426,8 +431,7 @@
 
     SKIP_BLANKS;
     if (ctxt->cur >= ctxt->end) {
-        virConfError(NULL, VIR_ERR_CONF_SYNTAX, _("expecting a value"),
-                     ctxt->line);
+        virConfError(ctxt, VIR_ERR_CONF_SYNTAX, _("expecting a value"));
         return(NULL);
     }
     if ((CUR == '"') || (CUR == '\'')) {
@@ -446,8 +450,8 @@
         }
         while ((ctxt->cur < ctxt->end) && (CUR != ']')) {
             if (CUR != ',') {
-                virConfError(NULL, VIR_ERR_CONF_SYNTAX,
-                             _("expecting a separator in list"), ctxt->line);
+                virConfError(ctxt, VIR_ERR_CONF_SYNTAX,
+                             _("expecting a separator in list"));
                 virConfFreeList(lst);
                 return(NULL);
             }
@@ -469,8 +473,8 @@
         if (CUR == ']') {
             NEXT;
         } else {
-            virConfError(NULL, VIR_ERR_CONF_SYNTAX,
-                         _("list is not closed with ]"), ctxt->line);
+            virConfError(ctxt, VIR_ERR_CONF_SYNTAX,
+                         _("list is not closed with ]"));
             virConfFreeList(lst);
             return(NULL);
         }
@@ -480,12 +484,11 @@
         }
         type = VIR_CONF_LONG;
     } else {
-        virConfError(NULL, VIR_ERR_CONF_SYNTAX, _("expecting a value"),
-                     ctxt->line);
+        virConfError(ctxt, VIR_ERR_CONF_SYNTAX, _("expecting a value"));
         return(NULL);
     }
     if (VIR_ALLOC(ret) < 0) {
-        virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocating configuration"), 0);
+        virConfError(ctxt, VIR_ERR_NO_MEMORY, _("allocating configuration"));
         virConfFreeList(lst);
         VIR_FREE(str);
         return(NULL);
@@ -515,15 +518,14 @@
     base = ctxt->cur;
     /* TODO: probably need encoding support and UTF-8 parsing ! */
     if (!c_isalpha(CUR)) {
-        virConfError(NULL, VIR_ERR_CONF_SYNTAX, _("expecting a name"), ctxt->line);
+        virConfError(ctxt, VIR_ERR_CONF_SYNTAX, _("expecting a name"));
         return(NULL);
     }
     while ((ctxt->cur < ctxt->end) && (c_isalnum(CUR) || (CUR == '_')))
         NEXT;
     ret = strndup(base, ctxt->cur - base);
     if (ret == NULL) {
-        virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocating configuration"),
-                     ctxt->line);
+        virConfError(ctxt, VIR_ERR_NO_MEMORY, _("allocating configuration"));
         return(NULL);
     }
     return(ret);
@@ -550,8 +552,7 @@
     while ((ctxt->cur < ctxt->end) && (!IS_EOL(CUR))) NEXT;
     comm = strndup(base, ctxt->cur - base);
     if (comm == NULL) {
-        virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocating configuration"),
-                     ctxt->line);
+        virConfError(ctxt, VIR_ERR_NO_MEMORY, _("allocating configuration"));
         return(-1);
     }
     virConfAddEntry(ctxt->conf, NULL, NULL, comm);
@@ -578,8 +579,7 @@
         NEXT;
         SKIP_BLANKS_AND_EOL;
     } else {
-        virConfError(NULL, VIR_ERR_CONF_SYNTAX, _("expecting a separator"),
-                     ctxt->line);
+        virConfError(ctxt, VIR_ERR_CONF_SYNTAX, _("expecting a separator"));
         return(-1);
     }
     return(0);
@@ -610,8 +610,7 @@
         return(-1);
     SKIP_BLANKS;
     if (CUR != '=') {
-        virConfError(NULL, VIR_ERR_CONF_SYNTAX, _("expecting an assignment"),
-                     ctxt->line);
+        virConfError(ctxt, VIR_ERR_CONF_SYNTAX, _("expecting an assignment"));
         return(-1);
     }
     NEXT;
@@ -628,8 +627,7 @@
         while ((ctxt->cur < ctxt->end) && (!IS_EOL(CUR))) NEXT;
         comm = strndup(base, ctxt->cur - base);
         if (comm == NULL) {
-            virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocating configuration"),
-                         ctxt->line);
+            virConfError(ctxt, VIR_ERR_NO_MEMORY, _("allocating configuration"));
             VIR_FREE(name);
             virConfFreeValue(value);
             return(-1);
@@ -709,12 +707,12 @@
     virConfPtr conf;
 
     if (filename == NULL) {
-        virConfError(NULL, VIR_ERR_INVALID_ARG, __FUNCTION__, 0);
+        virConfError(NULL, VIR_ERR_INVALID_ARG, __FUNCTION__);
         return(NULL);
     }
 
     if ((len = virFileReadAll(filename, MAX_CONFIG_FILE_SIZE, &content)) < 0) {
-        virConfError(NULL, VIR_ERR_OPEN_FAILED, filename, 0);
+        virConfError(NULL, VIR_ERR_OPEN_FAILED, filename);
         return NULL;
     }
 
@@ -740,7 +738,7 @@
 __virConfReadMem(const char *memory, int len)
 {
     if ((memory == NULL) || (len < 0)) {
-        virConfError(NULL, VIR_ERR_INVALID_ARG, __FUNCTION__, 0);
+        virConfError(NULL, VIR_ERR_INVALID_ARG, __FUNCTION__);
         return(NULL);
     }
     if (len == 0)
@@ -762,7 +760,7 @@
 {
     virConfEntryPtr tmp;
     if (conf == NULL) {
-        virConfError(NULL, VIR_ERR_INVALID_ARG, __FUNCTION__, 0);
+        virConfError(NULL, VIR_ERR_INVALID_ARG, __FUNCTION__);
         return(-1);
     }
 
@@ -891,14 +889,14 @@
     }
 
     if (virBufferError(&buf)) {
-        virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocate buffer"), 0);
+        virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocate buffer"));
         return -1;
     }
 
     fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR );
     if (fd < 0) {
         char *tmp = virBufferContentAndReset(&buf);
-        virConfError(NULL, VIR_ERR_WRITE_FAILED, _("failed to open file"), 0);
+        virConfError(NULL, VIR_ERR_WRITE_FAILED, _("failed to open file"));
         VIR_FREE(tmp);
         return -1;
     }
@@ -909,7 +907,7 @@
     VIR_FREE(content);
     close(fd);
     if (ret != (int)use) {
-        virConfError(NULL, VIR_ERR_WRITE_FAILED, _("failed to save content"), 0);
+        virConfError(NULL, VIR_ERR_WRITE_FAILED, _("failed to save content"));
         return -1;
     }
 
@@ -947,7 +945,7 @@
     }
 
     if (virBufferError(&buf)) {
-        virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocate buffer"), 0);
+        virConfError(NULL, VIR_ERR_NO_MEMORY, _("allocate buffer"));
         return -1;
     }
 

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