libxl, xl: don't free string literals in config structure

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.

[ fixed up for stray ! sign -iwj ]

Signed-off-by: Gianni Tedesco <gianni.tedesco@citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/tools/libxl/libxlu_cfg.c b/tools/libxl/libxlu_cfg.c
index 09a7c71eda..07e65e1043 100644
--- a/tools/libxl/libxlu_cfg.c
+++ b/tools/libxl/libxlu_cfg.c
@@ -151,7 +151,18 @@ int xlu_cfg_get_string(const XLU_Config *cfg, const char *n,
     *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;