X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/725184f3bce66a3eff87cc3a01e5d96477a5d28a..f780443504c3b73f0b9d1c58c6c5a21e2affce2d:/src/xbt/config.c

diff --git a/src/xbt/config.c b/src/xbt/config.c
index 7d663cb6c9..56213d5a16 100644
--- a/src/xbt/config.c
+++ b/src/xbt/config.c
@@ -1,10 +1,9 @@
-/* $Id$ */
-
 /* config - Dictionnary where the type of each variable is provided.            */
 
 /* This is useful to build named structs, like option or property sets.     */
 
-/* Copyright (c) 2001,2002,2003,2004 Martin Quinson. All rights reserved.   */
+/* Copyright (c) 2004, 2005, 2006, 2007, 2008, 2009, 2010. The SimGrid Team.
+ * All rights reserved.                                                     */
 
 /* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */
@@ -22,38 +21,12 @@
 
 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(xbt_cfg, xbt, "configuration support");
 
-/* xbt_cfgelm_t: the typedef corresponding to a config variable.
-
-   Both data and DTD are mixed, but fixing it now would prevent me to ever
-   defend my thesis. */
-
-typedef struct {
-  /* Description */
-  const char *desc;
-
-  /* Allowed type of the variable */
-  e_xbt_cfgelm_type_t type;
-  int min, max;
-
-  /* Callbacks */
-  xbt_cfg_cb_t cb_set;
-  xbt_cfg_cb_t cb_rm;
-
-  /* actual content
-     (cannot be an union because type peer uses both str and i) */
-  xbt_dynar_t content;
-} s_xbt_cfgelm_t, *xbt_cfgelm_t;
-
 static const char *xbt_cfgelm_type_name[xbt_cfgelm_type_count] =
-  { "int", "double", "string", "peer", "any" };
+    { "int", "double", "string", "peer", "any" };
 
 /* Internal stuff used in cache to free a variable */
 static void xbt_cfgelm_free(void *data);
 
-/* Retrieve the variable we'll modify */
-static xbt_cfgelm_t xbt_cfgelm_get(xbt_cfg_t cfg, const char *name,
-                                   e_xbt_cfgelm_type_t type);
-
 /*----[ Memory management ]-----------------------------------------------*/
 
 /** @brief Constructor
@@ -86,8 +59,9 @@ void xbt_cfg_cpy(xbt_cfg_t tocopy, xbt_cfg_t * whereto)
   xbt_assert0(tocopy, "cannot copy NULL config");
 
   xbt_dict_foreach((xbt_dict_t) tocopy, cursor, name, variable) {
-    xbt_cfg_register(whereto, name, variable->desc, variable->type, NULL, variable->min,
-                     variable->max, variable->cb_set, variable->cb_rm);
+    xbt_cfg_register(whereto, name, variable->desc, variable->type, NULL,
+                     variable->min, variable->max, variable->cb_set,
+                     variable->cb_rm);
   }
 }
 
@@ -125,9 +99,10 @@ void xbt_cfg_dump(const char *name, const char *indent, xbt_cfg_t cfg)
 
     size = xbt_dynar_length(variable->content);
     printf
-      ("%d_to_%d_%s. Actual size=%d. prerm=%p,postset=%p, List of values:\n",
-       variable->min, variable->max, xbt_cfgelm_type_name[variable->type],
-       size, variable->cb_rm, variable->cb_set);
+        ("%d_to_%d_%s. Actual size=%d. prerm=%p,postset=%p, List of values:\n",
+         variable->min, variable->max,
+         xbt_cfgelm_type_name[variable->type], size, variable->cb_rm,
+         variable->cb_set);
 
     switch (variable->type) {
 
@@ -184,6 +159,7 @@ void xbt_cfgelm_free(void *data)
   DEBUG1("Frees cfgelm %p", c);
   if (!c)
     return;
+  xbt_free(c->desc);
   xbt_dynar_free(&(c->content));
   free(c);
 }
@@ -199,18 +175,19 @@ void xbt_cfgelm_free(void *data)
  */
 
 void
-xbt_cfg_register(xbt_cfg_t *cfg,
-                 const char *name, const char *desc, e_xbt_cfgelm_type_t type, void *default_value,
-                 int min, int max, xbt_cfg_cb_t cb_set, xbt_cfg_cb_t cb_rm)
+xbt_cfg_register(xbt_cfg_t * cfg,
+                 const char *name, const char *desc,
+                 e_xbt_cfgelm_type_t type, void *default_value, int min,
+                 int max, xbt_cfg_cb_t cb_set, xbt_cfg_cb_t cb_rm)
 {
   xbt_cfgelm_t res;
 
-  if (*cfg==NULL)
-	 *cfg=xbt_cfg_new();
+  if (*cfg == NULL)
+    *cfg = xbt_cfg_new();
   xbt_assert4(type >= xbt_cfgelm_int && type <= xbt_cfgelm_peer,
               "type of %s not valid (%d should be between %d and %d)",
               name, type, xbt_cfgelm_int, xbt_cfgelm_peer);
-  res = xbt_dict_get_or_null((xbt_dict_t) *cfg, name);
+  res = xbt_dict_get_or_null((xbt_dict_t) * cfg, name);
 
   if (res) {
     WARN1("Config elem %s registered twice.", name);
@@ -219,45 +196,47 @@ xbt_cfg_register(xbt_cfg_t *cfg,
 
   res = xbt_new(s_xbt_cfgelm_t, 1);
   DEBUG8("Register cfg elm %s (%s) (%d to %d %s (=%d) @%p in set %p)",
-         name, desc, min, max, xbt_cfgelm_type_name[type], type, res, *cfg);
+         name, desc, min, max, xbt_cfgelm_type_name[type], type, res,
+         *cfg);
 
-  res->desc = desc;
+  res->desc = xbt_strdup(desc);
   res->type = type;
   res->min = min;
   res->max = max;
   res->cb_set = cb_set;
   res->cb_rm = cb_rm;
+  res->isdefault = 1;
 
   switch (type) {
   case xbt_cfgelm_int:
     res->content = xbt_dynar_new(sizeof(int), NULL);
     if (default_value)
-    	xbt_dynar_push(res->content,default_value);
+      xbt_dynar_push(res->content, default_value);
     break;
 
   case xbt_cfgelm_double:
     res->content = xbt_dynar_new(sizeof(double), NULL);
     if (default_value)
-    	xbt_dynar_push(res->content,default_value);
+      xbt_dynar_push(res->content, default_value);
     break;
 
   case xbt_cfgelm_string:
     res->content = xbt_dynar_new(sizeof(char *), xbt_free_ref);
     if (default_value)
-    	xbt_dynar_push(res->content,default_value);
+      xbt_dynar_push(res->content, default_value);
     break;
 
   case xbt_cfgelm_peer:
     res->content = xbt_dynar_new(sizeof(xbt_peer_t), xbt_peer_free_voidp);
     if (default_value)
-    	xbt_dynar_push(res->content,default_value);
+      xbt_dynar_push(res->content, default_value);
     break;
 
   default:
     ERROR1("%d is an invalide type code", type);
   }
 
-  xbt_dict_set((xbt_dict_t) *cfg, name, res, &xbt_cfgelm_free);
+  xbt_dict_set((xbt_dict_t) * cfg, name, res, &xbt_cfgelm_free);
 }
 
 /** @brief Unregister an element from a config set.
@@ -288,7 +267,7 @@ void xbt_cfg_unregister(xbt_cfg_t cfg, const char *name)
  * @fixme: this does not allow to set the description
  */
 
-void xbt_cfg_register_str(xbt_cfg_t *cfg, const char *entry)
+void xbt_cfg_register_str(xbt_cfg_t * cfg, const char *entry)
 {
   char *entrycpy = xbt_strdup(entry);
   char *tok;
@@ -303,7 +282,8 @@ void xbt_cfg_register_str(xbt_cfg_t *cfg, const char *entry)
   *(tok++) = '\0';
 
   min = strtol(tok, &tok, 10);
-  xbt_assert1(tok, "Invalid minimum in config element descriptor %s", entry);
+  xbt_assert1(tok, "Invalid minimum in config element descriptor %s",
+              entry);
 
   xbt_assert2(strcmp(tok, "_to_"),
               "Invalid config element descriptor : %s%s",
@@ -311,7 +291,8 @@ void xbt_cfg_register_str(xbt_cfg_t *cfg, const char *entry)
   tok += strlen("_to_");
 
   max = strtol(tok, &tok, 10);
-  xbt_assert1(tok, "Invalid maximum in config element descriptor %s", entry);
+  xbt_assert1(tok, "Invalid maximum in config element descriptor %s",
+              entry);
 
   xbt_assert2(*(tok++) == '_',
               "Invalid config element descriptor: %s%s", entry,
@@ -330,61 +311,67 @@ void xbt_cfg_register_str(xbt_cfg_t *cfg, const char *entry)
 }
 
 /** @brief Displays the declared options and their description */
-void xbt_cfg_help(xbt_cfg_t cfg) {
-	xbt_dict_cursor_t cursor;
-	xbt_cfgelm_t variable;
-	char *name;
-
-	  int i;
-	  int size;
-
-	xbt_dict_foreach((xbt_dict_t) cfg, cursor, name, variable) {
-		printf("   %s: %s\n",name,variable->desc);
-		printf("       Type: %s; ", xbt_cfgelm_type_name[variable->type]);
-		if (variable->min != 1 || variable->max != 1)
-			printf("Arrity: min:%d to max:%d; ",variable->min,variable->max);
-		printf("Current value: ");
-		size = xbt_dynar_length(variable->content);
-
-	    switch (variable->type) {
-		  int ival;
-		  char *sval;
-		  double dval;
-		  xbt_peer_t hval;
-
-	    case xbt_cfgelm_int:
-	      for (i = 0; i < size; i++) {
-	        ival = xbt_dynar_get_as(variable->content, i, int);
-	        printf("%s%d\n", (i==0?"":"              "),ival);
-	      }
-	      break;
-
-	    case xbt_cfgelm_double:
-	      for (i = 0; i < size; i++) {
-	        dval = xbt_dynar_get_as(variable->content, i, double);
-	        printf("%s%f\n", (i==0?"":"              "),dval);
-	      }
-	      break;
-
-	    case xbt_cfgelm_string:
-	      for (i = 0; i < size; i++) {
-	        sval = xbt_dynar_get_as(variable->content, i, char *);
-	        printf("%s'%s'\n", (i==0?"":"              "),sval);
-	      }
-	      break;
-
-	    case xbt_cfgelm_peer:
-	      for (i = 0; i < size; i++) {
-	        hval = xbt_dynar_get_as(variable->content, i, xbt_peer_t);
-	        printf("%s%s:%d\n", (i==0?"":"              "),hval->name, hval->port);
-	      }
-	      break;
-
-	    default:
-	      printf("Invalid type!!\n");
-	    }
-
-	}
+void xbt_cfg_help(xbt_cfg_t cfg)
+{
+  xbt_dict_cursor_t cursor;
+  xbt_cfgelm_t variable;
+  char *name;
+
+  int i;
+  int size;
+
+  xbt_dict_foreach((xbt_dict_t) cfg, cursor, name, variable) {
+    printf("   %s: %s\n", name, variable->desc);
+    printf("       Type: %s; ", xbt_cfgelm_type_name[variable->type]);
+    if (variable->min != 1 || variable->max != 1) {
+      if (variable->min == 0 && variable->max == 0)
+        printf("Arity: no bound; ");
+      else
+        printf("Arity: min:%d to max:%d; ", variable->min, variable->max);
+    }
+    printf("Current value: ");
+    size = xbt_dynar_length(variable->content);
+
+    switch (variable->type) {
+      int ival;
+      char *sval;
+      double dval;
+      xbt_peer_t hval;
+
+    case xbt_cfgelm_int:
+      for (i = 0; i < size; i++) {
+        ival = xbt_dynar_get_as(variable->content, i, int);
+        printf("%s%d\n", (i == 0 ? "" : "              "), ival);
+      }
+      break;
+
+    case xbt_cfgelm_double:
+      for (i = 0; i < size; i++) {
+        dval = xbt_dynar_get_as(variable->content, i, double);
+        printf("%s%f\n", (i == 0 ? "" : "              "), dval);
+      }
+      break;
+
+    case xbt_cfgelm_string:
+      for (i = 0; i < size; i++) {
+        sval = xbt_dynar_get_as(variable->content, i, char *);
+        printf("%s'%s'\n", (i == 0 ? "" : "              "), sval);
+      }
+      break;
+
+    case xbt_cfgelm_peer:
+      for (i = 0; i < size; i++) {
+        hval = xbt_dynar_get_as(variable->content, i, xbt_peer_t);
+        printf("%s%s:%d\n", (i == 0 ? "" : "              "), hval->name,
+               hval->port);
+      }
+      break;
+
+    default:
+      printf("Invalid type!!\n");
+    }
+
+  }
 }
 
 /** @brief Check that each variable have the right amount of values */
@@ -404,28 +391,31 @@ void xbt_cfg_check(xbt_cfg_t cfg)
       xbt_dict_cursor_free(&cursor);
       THROW4(mismatch_error, 0,
              "Config elem %s needs at least %d %s, but there is only %d values.",
-             name, variable->min, xbt_cfgelm_type_name[variable->type], size);
+             name, variable->min, xbt_cfgelm_type_name[variable->type],
+             size);
     }
 
     if (variable->max > 0 && variable->max < size) {
       xbt_dict_cursor_free(&cursor);
       THROW4(mismatch_error, 0,
              "Config elem %s accepts at most %d %s, but there is %d values.",
-             name, variable->max, xbt_cfgelm_type_name[variable->type], size);
+             name, variable->max, xbt_cfgelm_type_name[variable->type],
+             size);
     }
   }
 
   xbt_dict_cursor_free(&cursor);
 }
 
-static xbt_cfgelm_t xbt_cfgelm_get(xbt_cfg_t cfg,
-                                   const char *name, e_xbt_cfgelm_type_t type)
+xbt_cfgelm_t xbt_cfgelm_get(xbt_cfg_t cfg,
+                                   const char *name,
+                                   e_xbt_cfgelm_type_t type)
 {
   xbt_cfgelm_t res = NULL;
 
   res = xbt_dict_get_or_null((xbt_dict_t) cfg, name);
   if (!res) {
-	  xbt_cfg_help(cfg);
+    xbt_cfg_help(cfg);
     THROW1(not_found_error, 0,
            "No registered variable '%s' in this config set", name);
   }
@@ -486,7 +476,8 @@ void xbt_cfg_set_vargs(xbt_cfg_t cfg, const char *name, va_list pa)
     if (e.category == not_found_error) {
       xbt_ex_free(e);
       THROW1(not_found_error, 0,
-             "Can't set the property '%s' since it's not registered", name);
+             "Can't set the property '%s' since it's not registered",
+             name);
     }
     RETHROW;
   }
@@ -618,6 +609,7 @@ void xbt_cfg_set_parse(xbt_cfg_t cfg, const char *options)
     }
     *(val++) = '\0';
 
+    if(strcmp(name,"simix/context"))
     INFO2("Configuration change: Set '%s' to '%s'", name, val);
 
     TRY {
@@ -630,7 +622,7 @@ void xbt_cfg_set_parse(xbt_cfg_t cfg, const char *options)
       if (e.category == not_found_error) {
         xbt_ex_free(e);
         THROW1(not_found_error, 0,
-               "No registrated variable corresponding to '%s'.", name);
+               "No registered variable corresponding to '%s'.", name);
       }
       RETHROW;
     }
@@ -701,6 +693,84 @@ void xbt_cfg_set_parse(xbt_cfg_t cfg, const char *options)
 
 }
 
+/** @brief Set an integer value to \a name within \a cfg if it wasn't changed yet
+ *
+ * This is useful to change the default value of a variable while allowing
+ * users to override it with command line arguments
+ */
+void xbt_cfg_setdefault_int(xbt_cfg_t cfg, const char *name, int val)
+{
+  xbt_cfgelm_t variable = xbt_cfgelm_get(cfg, name, xbt_cfgelm_int);
+
+  if (variable->isdefault){
+    xbt_cfg_set_int(cfg, name, val);
+    variable->isdefault = 1;
+  }
+   else
+    DEBUG2
+        ("Do not override configuration variable '%s' with value '%d' because it was already set.",
+         name, val);
+}
+
+/** @brief Set an integer value to \a name within \a cfg if it wasn't changed yet
+ *
+ * This is useful to change the default value of a variable while allowing
+ * users to override it with command line arguments
+ */
+void xbt_cfg_setdefault_double(xbt_cfg_t cfg, const char *name, double val)
+{
+  xbt_cfgelm_t variable = xbt_cfgelm_get(cfg, name, xbt_cfgelm_double);
+
+  if (variable->isdefault) {
+    xbt_cfg_set_double(cfg, name, val);
+    variable->isdefault = 1;
+  }
+  else
+    DEBUG2
+        ("Do not override configuration variable '%s' with value '%lf' because it was already set.",
+         name, val);
+}
+
+/** @brief Set a string value to \a name within \a cfg if it wasn't changed yet
+ *
+ * This is useful to change the default value of a variable while allowing
+ * users to override it with command line arguments
+ */
+void xbt_cfg_setdefault_string(xbt_cfg_t cfg, const char *name,
+                               const char *val)
+{
+  xbt_cfgelm_t variable = xbt_cfgelm_get(cfg, name, xbt_cfgelm_string);
+
+  if (variable->isdefault){
+    xbt_cfg_set_string(cfg, name, val);
+    variable->isdefault = 1;
+  }
+  else
+    DEBUG2
+        ("Do not override configuration variable '%s' with value '%s' because it was already set.",
+         name, val);
+}
+
+/** @brief Set a peer value to \a name within \a cfg if it wasn't changed yet
+ *
+ * This is useful to change the default value of a variable while allowing
+ * users to override it with command line arguments
+ */
+void xbt_cfg_setdefault_peer(xbt_cfg_t cfg, const char *name,
+                             const char *host, int port)
+{
+  xbt_cfgelm_t variable = xbt_cfgelm_get(cfg, name, xbt_cfgelm_peer);
+
+  if (variable->isdefault){
+    xbt_cfg_set_peer(cfg, name, host, port);
+    variable->isdefault = 1;
+  }
+  else
+    DEBUG3
+        ("Do not override configuration variable '%s' with value '%s:%d' because it was already set.",
+         name, host, port);
+}
+
 /** @brief Set or add an integer value to \a name within \a cfg
  *
  * \arg cfg the config set
@@ -732,6 +802,7 @@ void xbt_cfg_set_int(xbt_cfg_t cfg, const char *name, int val)
 
   if (variable->cb_set)
     (*variable->cb_set) (name, xbt_dynar_length(variable->content) - 1);
+  variable->isdefault = 0;
 }
 
 /** @brief Set or add a double value to \a name within \a cfg
@@ -754,7 +825,8 @@ void xbt_cfg_set_double(xbt_cfg_t cfg, const char *name, double val)
 
     xbt_dynar_set(variable->content, 0, &val);
   } else {
-    if (variable->max && xbt_dynar_length(variable->content) == variable->max)
+    if (variable->max
+        && xbt_dynar_length(variable->content) == variable->max)
       THROW3(mismatch_error, 0,
              "Cannot add value %f to the config element %s since it's already full (size=%d)",
              val, name, variable->max);
@@ -764,6 +836,7 @@ void xbt_cfg_set_double(xbt_cfg_t cfg, const char *name, double val)
 
   if (variable->cb_set)
     (*variable->cb_set) (name, xbt_dynar_length(variable->content) - 1);
+  variable->isdefault = 0;
 }
 
 /** @brief Set or add a string value to \a name within \a cfg
@@ -782,8 +855,8 @@ void xbt_cfg_set_string(xbt_cfg_t cfg, const char *name, const char *val)
   VERB2("Configuration setting: %s=%s", name, val);
   variable = xbt_cfgelm_get(cfg, name, xbt_cfgelm_string);
   DEBUG5("Variable: %d to %d %s (=%d) @%p",
-         variable->min, variable->max, xbt_cfgelm_type_name[variable->type],
-         variable->type, variable);
+         variable->min, variable->max,
+         xbt_cfgelm_type_name[variable->type], variable->type, variable);
 
   if (variable->max == 1) {
     if (xbt_dynar_length(variable->content)) {
@@ -797,7 +870,8 @@ void xbt_cfg_set_string(xbt_cfg_t cfg, const char *name, const char *val)
 
     xbt_dynar_set(variable->content, 0, &newval);
   } else {
-    if (variable->max && xbt_dynar_length(variable->content) == variable->max)
+    if (variable->max
+        && xbt_dynar_length(variable->content) == variable->max)
       THROW3(mismatch_error, 0,
              "Cannot add value %s to the config element %s since it's already full (size=%d)",
              name, val, variable->max);
@@ -807,6 +881,7 @@ void xbt_cfg_set_string(xbt_cfg_t cfg, const char *name, const char *val)
 
   if (variable->cb_set)
     (*variable->cb_set) (name, xbt_dynar_length(variable->content) - 1);
+  variable->isdefault = 0;
 }
 
 /** @brief Set or add an peer value to \a name within \a cfg
@@ -820,7 +895,8 @@ void xbt_cfg_set_string(xbt_cfg_t cfg, const char *name, const char *val)
  */
 
 void
-xbt_cfg_set_peer(xbt_cfg_t cfg, const char *name, const char *peer, int port)
+xbt_cfg_set_peer(xbt_cfg_t cfg, const char *name, const char *peer,
+                 int port)
 {
   xbt_cfgelm_t variable;
   xbt_peer_t val = xbt_peer_new(peer, port);
@@ -835,7 +911,8 @@ xbt_cfg_set_peer(xbt_cfg_t cfg, const char *name, const char *peer, int port)
 
     xbt_dynar_set(variable->content, 0, &val);
   } else {
-    if (variable->max && xbt_dynar_length(variable->content) == variable->max)
+    if (variable->max
+        && xbt_dynar_length(variable->content) == variable->max)
       THROW4(mismatch_error, 0,
              "Cannot add value %s:%d to the config element %s since it's already full (size=%d)",
              peer, port, name, variable->max);
@@ -845,6 +922,7 @@ xbt_cfg_set_peer(xbt_cfg_t cfg, const char *name, const char *peer, int port)
 
   if (variable->cb_set)
     (*variable->cb_set) (name, xbt_dynar_length(variable->content) - 1);
+  variable->isdefault = 0;
 }
 
 /* ---- [ Removing ] ---- */
@@ -959,7 +1037,8 @@ void xbt_cfg_rm_string(xbt_cfg_t cfg, const char *name, const char *val)
  */
 
 void
-xbt_cfg_rm_peer(xbt_cfg_t cfg, const char *name, const char *peer, int port)
+xbt_cfg_rm_peer(xbt_cfg_t cfg, const char *name, const char *peer,
+                int port)
 {
   xbt_cfgelm_t variable;
   unsigned int cpt;
@@ -1060,8 +1139,8 @@ int xbt_cfg_get_int(xbt_cfg_t cfg, const char *name)
 
   if (xbt_dynar_length(variable->content) > 1) {
     WARN2
-      ("You asked for the first value of the config element '%s', but there is %lu values",
-       name, xbt_dynar_length(variable->content));
+        ("You asked for the first value of the config element '%s', but there is %lu values",
+         name, xbt_dynar_length(variable->content));
   }
 
   return xbt_dynar_get_as(variable->content, 0, int);
@@ -1086,8 +1165,8 @@ double xbt_cfg_get_double(xbt_cfg_t cfg, const char *name)
 
   if (xbt_dynar_length(variable->content) > 1) {
     WARN2
-      ("You asked for the first value of the config element '%s', but there is %lu values\n",
-       name, xbt_dynar_length(variable->content));
+        ("You asked for the first value of the config element '%s', but there is %lu values\n",
+         name, xbt_dynar_length(variable->content));
   }
 
   return xbt_dynar_get_as(variable->content, 0, double);
@@ -1101,7 +1180,7 @@ double xbt_cfg_get_double(xbt_cfg_t cfg, const char *name)
  *
  * Returns the first value from the config set under the given name.
  * If there is more than one value, it will issue a warning. Consider using
- * xbt_cfg_get_dynar() instead.
+ * xbt_cfg_get_dynar() instead. Returns NULL if there is no value.
  *
  * \warning the returned value is the actual content of the config set
  */
@@ -1112,8 +1191,10 @@ char *xbt_cfg_get_string(xbt_cfg_t cfg, const char *name)
 
   if (xbt_dynar_length(variable->content) > 1) {
     WARN2
-      ("You asked for the first value of the config element '%s', but there is %lu values\n",
-       name, xbt_dynar_length(variable->content));
+        ("You asked for the first value of the config element '%s', but there is %lu values\n",
+         name, xbt_dynar_length(variable->content));
+  } else if (xbt_dynar_length(variable->content) == 0) {
+    return NULL;
   }
 
   return xbt_dynar_get_as(variable->content, 0, char *);
@@ -1133,7 +1214,8 @@ char *xbt_cfg_get_string(xbt_cfg_t cfg, const char *name)
  * \warning the returned value is the actual content of the config set
  */
 
-void xbt_cfg_get_peer(xbt_cfg_t cfg, const char *name, char **peer, int *port)
+void xbt_cfg_get_peer(xbt_cfg_t cfg, const char *name, char **peer,
+                      int *port)
 {
   xbt_cfgelm_t variable;
   xbt_peer_t val;
@@ -1142,8 +1224,8 @@ void xbt_cfg_get_peer(xbt_cfg_t cfg, const char *name, char **peer, int *port)
 
   if (xbt_dynar_length(variable->content) > 1) {
     WARN2
-      ("You asked for the first value of the config element '%s', but there is %lu values\n",
-       name, xbt_dynar_length(variable->content));
+        ("You asked for the first value of the config element '%s', but there is %lu values\n",
+         name, xbt_dynar_length(variable->content));
   }
 
   val = xbt_dynar_get_as(variable->content, 0, xbt_peer_t);
@@ -1225,6 +1307,7 @@ xbt_cfg_get_peer_at(xbt_cfg_t cfg, const char *name, int pos,
 #include "xbt/ex.h"
 
 XBT_LOG_EXTERNAL_CATEGORY(xbt_cfg);
+XBT_LOG_DEFAULT_CATEGORY(xbt_cfg);
 
 XBT_TEST_SUITE("config", "Configuration support");
 
@@ -1232,7 +1315,7 @@ static xbt_cfg_t make_set()
 {
   xbt_cfg_t set = NULL;
 
-  xbt_log_threshold_set(&_XBT_LOGV(xbt_cfg),xbt_log_priority_critical);
+  xbt_log_threshold_set(&_XBT_LOGV(xbt_cfg), xbt_log_priority_critical);
   xbt_cfg_register_str(&set, "speed:1_to_2_int");
   xbt_cfg_register_str(&set, "peername:1_to_1_string");
   xbt_cfg_register_str(&set, "user:1_to_10_string");
@@ -1314,7 +1397,8 @@ XBT_TEST_UNIT("use", test_config_use, "Data retrieving tests")
     xbt_dynar_t dyn;
     xbt_cfg_t myset = make_set();
 
-    xbt_cfg_set_parse(myset, "peername:veloce user:foo\nuser:bar\tuser:toto");
+    xbt_cfg_set_parse(myset,
+                      "peername:veloce user:foo\nuser:bar\tuser:toto");
     xbt_cfg_set_parse(myset, "speed:42");
     xbt_cfg_check(myset);
     dyn = xbt_cfg_get_dynar(myset, "user");
@@ -1324,16 +1408,16 @@ XBT_TEST_UNIT("use", test_config_use, "Data retrieving tests")
                      xbt_dynar_length(dyn));
 
     if (strcmp(xbt_dynar_get_as(dyn, 0, char *), "foo"))
-        xbt_test_fail1("Dynar[0] = %s, I expected foo",
-                       xbt_dynar_get_as(dyn, 0, char *));
+       xbt_test_fail1("Dynar[0] = %s, I expected foo",
+                      xbt_dynar_get_as(dyn, 0, char *));
 
     if (strcmp(xbt_dynar_get_as(dyn, 1, char *), "bar"))
-        xbt_test_fail1("Dynar[1] = %s, I expected bar",
-                       xbt_dynar_get_as(dyn, 1, char *));
+       xbt_test_fail1("Dynar[1] = %s, I expected bar",
+                      xbt_dynar_get_as(dyn, 1, char *));
 
     if (strcmp(xbt_dynar_get_as(dyn, 2, char *), "toto"))
-        xbt_test_fail1("Dynar[2] = %s, I expected toto",
-                       xbt_dynar_get_as(dyn, 2, char *));
+       xbt_test_fail1("Dynar[2] = %s, I expected toto",
+                      xbt_dynar_get_as(dyn, 2, char *));
     xbt_cfg_free(&myset);
   }
 
@@ -1353,4 +1437,4 @@ XBT_TEST_UNIT("use", test_config_use, "Data retrieving tests")
     xbt_cfg_free(&myset);
   }
 }
-#endif /* SIMGRID_TEST */
+#endif                          /* SIMGRID_TEST */