[Xen-devel] [PATCH,v2]: xl: don't free string literals

[Gianni Tedesco <gianni.tedesco@xxxxxxxxxx>]

The function init_dm_info() is initialising some strings from literals.
This is bad juju because when the destructor is called we cannot know if
the string literal was overridden with a strdup()'d value. Therefore
strdup values in the initialiser then introduce and use the function
libxlu_cfg_replace_string() which free's whatever is set before
strdupping the new value on top of it. The rule for the new call should
be clear due to const vs. non-const arguments - changing the behaviour
of libxlu_cfg_get_string() would cause more complexity than it saves.

Signed-off-by: Gianni Tedesco <gianni.tedesco@xxxxxxxxxx>

diff -r e14a3c281982 tools/libxl/libxlu_cfg.c
--- a/tools/libxl/libxlu_cfg.c  Wed Sep 08 16:54:16 2010 +0100
+++ b/tools/libxl/libxlu_cfg.c  Wed Sep 08 17:27:05 2010 +0100
@@ -151,7 +151,18 @@ int xlu_cfg_get_string(const XLU_Config 
     *value_r= set->values[0];
     return 0;
 }
-        
+ 
+int xlu_cfg_replace_string(const XLU_Config *cfg, const char *n,
+                           char **value_r) {
+    XLU_ConfigSetting *set;
+    int e;
+
+    e= find_atom(cfg,n,&set);  if (e) return e;
+    free(*value_r);
+    *value_r= strdup(set->values[0]);
+    return 0;
+}
+
 int xlu_cfg_get_long(const XLU_Config *cfg, const char *n,
                      long *value_r) {
     long l;
diff -r e14a3c281982 tools/libxl/libxlutil.h
--- a/tools/libxl/libxlutil.h   Wed Sep 08 16:54:16 2010 +0100
+++ b/tools/libxl/libxlutil.h   Wed Sep 08 17:27:05 2010 +0100
@@ -46,6 +46,7 @@ void xlu_cfg_destroy(XLU_Config*);
  */
 
 int xlu_cfg_get_string(const XLU_Config*, const char *n, const char **value_r);
+int xlu_cfg_replace_string(const XLU_Config *cfg, const char *n, char 
**value_r); /* free/strdup version */
 int xlu_cfg_get_long(const XLU_Config*, const char *n, long *value_r);
 
 int xlu_cfg_get_list(const XLU_Config*, const char *n,
diff -r e14a3c281982 tools/libxl/xl_cmdimpl.c
--- a/tools/libxl/xl_cmdimpl.c  Wed Sep 08 16:54:16 2010 +0100
+++ b/tools/libxl/xl_cmdimpl.c  Wed Sep 08 17:27:05 2010 +0100
@@ -297,7 +297,7 @@ static void init_dm_info(libxl_device_mo
     libxl_uuid_generate(&dm_info->uuid);
 
     dm_info->dom_name = c_info->name;
-    dm_info->device_model = "qemu-dm";
+    dm_info->device_model = strdup("qemu-dm");
     dm_info->videoram = b_info->video_memkb / 1024;
     dm_info->apic = b_info->u.hvm.apic;
     dm_info->vcpus = b_info->max_vcpus;
@@ -305,7 +305,7 @@ static void init_dm_info(libxl_device_mo
 
     dm_info->stdvga = 0;
     dm_info->vnc = 1;
-    dm_info->vnclisten = "127.0.0.1";
+    dm_info->vnclisten = strdup("127.0.0.1");
     dm_info->vncdisplay = 0;
     dm_info->vncunused = 1;
     dm_info->keymap = NULL;
@@ -313,7 +313,7 @@ static void init_dm_info(libxl_device_mo
     dm_info->opengl = 0;
     dm_info->nographic = 0;
     dm_info->serial = NULL;
-    dm_info->boot = "cda";
+    dm_info->boot = strdup("cda");
     dm_info->usb = 0;
     dm_info->usbdevice = NULL;
     dm_info->xen_platform_pci = 1;
@@ -1022,38 +1022,30 @@ skip_vfb:
         init_dm_info(dm_info, c_info, b_info);
 
         /* then process config related to dm */
-        if (!xlu_cfg_get_string (config, "device_model", &buf))
-            dm_info->device_model = strdup(buf);
+        !xlu_cfg_replace_string (config, "device_model", 
&dm_info->device_model);
         if (!xlu_cfg_get_long (config, "stdvga", &l))
             dm_info->stdvga = l;
         if (!xlu_cfg_get_long (config, "vnc", &l))
             dm_info->vnc = l;
-        if (!xlu_cfg_get_string (config, "vnclisten", &buf))
-            dm_info->vnclisten = strdup(buf);
-        if (!xlu_cfg_get_string (config, "vncpasswd", &buf))
-            dm_info->vncpasswd = strdup(buf);
+        xlu_cfg_replace_string (config, "vnclisten", &dm_info->vnclisten);
+        xlu_cfg_replace_string (config, "vncpasswd", &dm_info->vncpasswd);
         if (!xlu_cfg_get_long (config, "vncdisplay", &l))
             dm_info->vncdisplay = l;
         if (!xlu_cfg_get_long (config, "vncunused", &l))
             dm_info->vncunused = l;
-        if (!xlu_cfg_get_string (config, "keymap", &buf))
-            dm_info->keymap = strdup(buf);
+        xlu_cfg_replace_string (config, "keymap", &dm_info->keymap);
         if (!xlu_cfg_get_long (config, "sdl", &l))
             dm_info->sdl = l;
         if (!xlu_cfg_get_long (config, "opengl", &l))
             dm_info->opengl = l;
         if (!xlu_cfg_get_long (config, "nographic", &l))
             dm_info->nographic = l;
-        if (!xlu_cfg_get_string (config, "serial", &buf))
-            dm_info->serial = strdup(buf);
-        if (!xlu_cfg_get_string (config, "boot", &buf))
-            dm_info->boot = strdup(buf);
+        xlu_cfg_replace_string (config, "serial", &dm_info->serial);
+        xlu_cfg_replace_string (config, "boot", &dm_info->boot);
         if (!xlu_cfg_get_long (config, "usb", &l))
             dm_info->usb = l;
-        if (!xlu_cfg_get_string (config, "usbdevice", &buf))
-            dm_info->usbdevice = strdup(buf);
-        if (!xlu_cfg_get_string (config, "soundhw", &buf))
-            dm_info->soundhw = strdup(buf);
+        xlu_cfg_replace_string (config, "usbdevice", &dm_info->usbdevice);
+        xlu_cfg_replace_string (config, "soundhw", &dm_info->soundhw);
         if (!xlu_cfg_get_long (config, "xen_platform_pci", &l))
             dm_info->xen_platform_pci = l;
     }



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