env: delete selected vars not present in imported env

When variables explicitly specified on the command line are not present
in the imported env, delete them from the running env.
If the variable is also missing from the running env, issue a warning.

Signed-off-by: Gerlando Falauto <gerlando.falauto@keymile.com>
Reviewed-by: Marek Vasut <marex@denx.de>

lib/hashtable.c

@@ -607,22 +607,32 @@ ssize_t hexport_r(struct hsearch_data *htab, const char sep,
  * himport()
  */
 
-/* Check whether variable name is amongst vars[] */
-static int is_var_in_set(const char *name, int nvars, char * const vars[])
+/*
+ * Check whether variable 'name' is amongst vars[],
+ * and remove all instances by setting the pointer to NULL
+ */
+static int drop_var_from_set(const char *name, int nvars, char * vars[])
 {
 	int i = 0;
+	int res = 0;
 
 	/* No variables specified means process all of them */
 	if (nvars == 0)
 		return 1;
 
 	for (i = 0; i < nvars; i++) {
-		if (!strcmp(name, vars[i]))
-			return 1;
+		if (vars[i] == NULL)
+			continue;
+		/* If we found it, delete all of them */
+		if (!strcmp(name, vars[i])) {
+			vars[i] = NULL;
+			res = 1;
+		}
 	}
-	debug("Skipping non-listed variable %s\n", name);
+	if (!res)
+		debug("Skipping non-listed variable %s\n", name);
 
-	return 0;
+	return res;
 }
 
 /*
@@ -665,6 +675,8 @@ int himport_r(struct hsearch_data *htab,
 		int nvars, char * const vars[], int do_apply)
 {
 	char *data, *sp, *dp, *name, *value;
+	char *localvars[nvars];
+	int i;
 
 	/* Test for correct arguments.  */
 	if (htab == NULL) {
@@ -681,6 +693,10 @@ int himport_r(struct hsearch_data *htab,
 	memcpy(data, env, size);
 	dp = data;
 
+	/* make a local copy of the list of variables */
+	if (nvars)
+		memcpy(localvars, vars, sizeof(vars[0]) * nvars);
+
 	if ((flag & H_NOCLEAR) == 0) {
 		/* Destroy old hash table if one exists */
 		debug("Destroy Hash Table: %p table = %p\n", htab,
@@ -749,7 +765,7 @@ int himport_r(struct hsearch_data *htab,
 			*dp++ = '\0';	/* terminate name */
 
 			debug("DELETE CANDIDATE: \"%s\"\n", name);
-			if (!is_var_in_set(name, nvars, vars))
+			if (!drop_var_from_set(name, nvars, localvars))
 				continue;
 
 			if (hdelete_r(name, htab, do_apply) == 0)
@@ -769,7 +785,7 @@ int himport_r(struct hsearch_data *htab,
 		++dp;
 
 		/* Skip variables which are not supposed to be processed */
-		if (!is_var_in_set(name, nvars, vars))
+		if (!drop_var_from_set(name, nvars, localvars))
 			continue;
 
 		/* enter into hash table */
@@ -809,6 +825,24 @@ int himport_r(struct hsearch_data *htab,
 	debug("INSERT: free(data = %p)\n", data);
 	free(data);
 
+	/* process variables which were not considered */
+	for (i = 0; i < nvars; i++) {
+		if (localvars[i] == NULL)
+			continue;
+		/*
+		 * All variables which were not deleted from the variable list
+		 * were not present in the imported env
+		 * This could mean two things:
+		 * a) if the variable was present in current env, we delete it
+		 * b) if the variable was not present in current env, we notify
+		 *    it might be a typo
+		 */
+		if (hdelete_r(localvars[i], htab, do_apply) == 0)
+			printf("WARNING: '%s' neither in running nor in imported env!\n", localvars[i]);
+		else
+			printf("WARNING: '%s' not in imported env, deleting it!\n", localvars[i]);
+	}
+
 	debug("INSERT: done\n");
 	return 1;		/* everything OK */
 }