Add extra sanity checks to jstrencode/jstrdecode

The function free_jstring_list() now takes a 'struct jstring
**jstring_list' and if not NULL it will set *jstring_list to NULL, after
freeing the list, in case the caller does something silly. Even so, the
two tools now set the list to NULL after calling the free function.

CHANGES.md

@@ -37,6 +37,12 @@ generated code, perhaps in a torture chamber or something like that, or for
 those who want hallucinations or nightmares :-) or simply those who are really
 curious what flex does.
 
+Add extra sanity checks to `jstrencode(1)` and `jstrdecode(1)` when freeing the
+lists. The function `free_jstring_list()` now takes a `struct jstring
+**jstring_list` and if not NULL it will set `*jstring_list` to NULL, after
+freeing the list, in case the caller does something silly. Even so, the two
+tools now set the list to NULL after calling the free function.
+
 
 ## Release 2.0.0 2024-10-31
 

jstr_util.c

@@ -155,28 +155,35 @@ free_jstring(struct jstring **jstr)
  *
  * given:
  *
- *  jstring_list    pointer to list to free
+ *  jstring_list    pointer to pointer to list to free
  *
- * This function takes a struct jstring *, a pointer to a linked list of struct
+ * This function takes a struct jstring **, a pointer to a linked list of struct
  * jstring *.
  *
  * NOTE: it is ASSUMED that the string in each struct jstring * is allocated on
  * the stack due to how the encoding/decoding works. If this is not the case
  * then expect errors.
+ *
+ * NOTE: if jstring_list is NULL then nothing is done.
  */
 void
-free_jstring_list(struct jstring *jstring_list)
+free_jstring_list(struct jstring **jstring_list)
 {
     struct jstring *jstr = NULL;    /* current in list */
     struct jstring *jstr_next = NULL;	/* next in list */
 
-    for (jstr = jstring_list; jstr != NULL; jstr = jstr_next) {
+
+    for (jstr = jstring_list != NULL ? *jstring_list : NULL; jstr != NULL; jstr = jstr_next) {
 	jstr_next = jstr->next;		/* get next in list before we free the current */
 
 	/* free current json string */
 	free_jstring(&jstr);
 	jstr = NULL;
     }
 
+    if (jstring_list != NULL) {
+        *jstring_list = NULL;
+    }
+
     jstring_list = NULL;
 }

jstr_util.h

@@ -75,6 +75,6 @@ struct jstring
 extern struct jstring *alloc_jstr(char *string, size_t bufsiz);
 extern int parse_entertainment(char const *optarg);
 extern void free_jstring(struct jstring **jstr);
-extern void free_jstring_list(struct jstring *jstring_list);
+extern void free_jstring_list(struct jstring **jstring_list);
 
 #endif /* INCLUDE_JSTR_UTIL_H */

jstrdecode.c

@@ -703,7 +703,8 @@ main(int argc, char **argv)
     /*
      * free list of decoded strings
      */
-    free_jstring_list(json_decoded_strings);
+    free_jstring_list(&json_decoded_strings);
+    json_decoded_strings = NULL;
 
     /*
      * All Done!!! All Done!!! -- Jessica Noll, Age 2

jstrdecode.h

@@ -69,7 +69,7 @@
 /*
  * official jstrdecode version
  */
-#define JSTRDECODE_VERSION "2.0.0 2024-10-31"	/* format: major.minor YYYY-MM-DD */
+#define JSTRDECODE_VERSION "2.0.1 2024-11-01"	/* format: major.minor YYYY-MM-DD */
 
 
 /*

jstrencode.c

@@ -604,7 +604,8 @@ main(int argc, char **argv)
     /*
      * free list of encoded strings
      */
-    free_jstring_list(json_encoded_strings);
+    free_jstring_list(&json_encoded_strings);
+    json_encoded_strings = NULL;
 
     /*
      * All Done!!! All Done!!! -- Jessica Noll, Age 2

jstrencode.h

@@ -69,7 +69,7 @@
 /*
  * official jstrencode version
  */
-#define JSTRENCODE_VERSION "2.0.0 2024-10-31"	/* format: major.minor YYYY-MM-DD */
+#define JSTRENCODE_VERSION "2.0.1 2024-11-01"	/* format: major.minor YYYY-MM-DD */
 
 
 /*