diff --git a/apps/restconf/clixon_restconf.h b/apps/restconf/clixon_restconf.h
index 2c23f61d..2f7861e2 100644
--- a/apps/restconf/clixon_restconf.h
+++ b/apps/restconf/clixon_restconf.h
@@ -63,8 +63,8 @@ int   restconf_terminate(clicon_handle h);
 int   restconf_insert_attributes(cxobj *xdata, cvec *qvec);
 int   restconf_main_extension_cb(clicon_handle h, yang_stmt *yext, yang_stmt *ys);
 /* also in restconf_handle.h */
-char *restconf_param_get(clicon_handle h, char *param);
-int   restconf_param_set(clicon_handle h, char *param, char *val);
+char *restconf_param_get(clicon_handle h, const char *param);
+int   restconf_param_set(clicon_handle h, const char *param, char *val);
 
 #endif /* _CLIXON_RESTCONF_H_ */
 
diff --git a/apps/restconf/restconf_api.h b/apps/restconf/restconf_api.h
index 21ab31da..ad23b765 100644
--- a/apps/restconf/restconf_api.h
+++ b/apps/restconf/restconf_api.h
@@ -42,9 +42,9 @@
  * Prototypes
  */
 #if defined(__GNUC__) && __GNUC__ >= 3
-int restconf_reply_header(void *req, char *name, char *vfmt, ...)  __attribute__ ((format (printf, 3, 4)));
+int restconf_reply_header(void *req, char *name, const char *vfmt, ...)  __attribute__ ((format (printf, 3, 4)));
 #else
-int restconf_reply_header(FCGX_Request *req, char *name, char *vfmt, ...);
+int restconf_reply_header(FCGX_Request *req, char *name, const char *vfmt, ...);
 #endif
 
 int restconf_reply_send(void *req, int code, cbuf *cb);
diff --git a/apps/restconf/restconf_api_fcgi.c b/apps/restconf/restconf_api_fcgi.c
index e7369bea..595b3f35 100644
--- a/apps/restconf/restconf_api_fcgi.c
+++ b/apps/restconf/restconf_api_fcgi.c
@@ -90,7 +90,7 @@ restconf_reply_body_start(void  *req0)
 int
 restconf_reply_header(void   *req0,
 		      char   *name,
-		      char   *vfmt,
+		      const char   *vfmt,
 		      ...)
 {
     FCGX_Request *req = (FCGX_Request *)req0;
diff --git a/apps/restconf/restconf_handle.c b/apps/restconf/restconf_handle.c
index 53348b67..84474f68 100644
--- a/apps/restconf/restconf_handle.c
+++ b/apps/restconf/restconf_handle.c
@@ -119,7 +119,7 @@ restconf_handle_exit(clicon_handle h)
  */
 char *
 restconf_param_get(clicon_handle h,
-		   char         *param)
+		   const char   *param)
 {
     struct restconf_handle *rh = handle(h);
 
@@ -138,7 +138,7 @@ restconf_param_get(clicon_handle h,
  */
 int
 restconf_param_set(clicon_handle h,
-		   char         *param,
+		   const char   *param,
 		   char         *val)
 {
     struct restconf_handle *rh = handle(h);
diff --git a/apps/restconf/restconf_handle.h b/apps/restconf/restconf_handle.h
index 464dd50d..7d286099 100644
--- a/apps/restconf/restconf_handle.h
+++ b/apps/restconf/restconf_handle.h
@@ -44,8 +44,8 @@
  */
 clicon_handle restconf_handle_init(void);
 int           restconf_handle_exit(clicon_handle h);
-char         *restconf_param_get(clicon_handle h, char *param);
-int           restconf_param_set(clicon_handle h, char *param, char *val);
+char         *restconf_param_get(clicon_handle h, const char *param);
+int           restconf_param_set(clicon_handle h, const char *param, char *val);
 int           restconf_param_del_all(clicon_handle h);
 
 #endif  /* _RESTCONF_HANDLE_H_ */
diff --git a/example/main/example_backend.c b/example/main/example_backend.c
index 1f76e373..6d00bf6d 100644
--- a/example/main/example_backend.c
+++ b/example/main/example_backend.c
@@ -538,7 +538,7 @@ static const map_str2str namespace_map[] = {
  */
 int
 example_upgrade(clicon_handle    h,
-		char            *db,
+		const char      *db,
 		cxobj           *xt,
 		modstate_diff_t *msd)
 {
diff --git a/lib/clixon/clixon_data.h b/lib/clixon/clixon_data.h
index fe619d24..154af55b 100644
--- a/lib/clixon/clixon_data.h
+++ b/lib/clixon/clixon_data.h
@@ -55,9 +55,9 @@ typedef struct {
 /*
  * Prototypes
  */
-int clicon_data_get(clicon_handle h, char *id, char **val);
-int clicon_data_set(clicon_handle h, char *id, char *val);
-int clicon_data_del(clicon_handle h, char *name);
+int clicon_data_get(clicon_handle h, const char *name, char **val);
+int clicon_data_set(clicon_handle h, const char *name, char *val);
+int clicon_data_del(clicon_handle h, const char *name);
 
 yang_stmt * clicon_dbspec_yang(clicon_handle h);
 int clicon_dbspec_yang_set(clicon_handle h, yang_stmt *ys);
diff --git a/lib/clixon/clixon_datastore.h b/lib/clixon/clixon_datastore.h
index 56515de7..478280b8 100644
--- a/lib/clixon/clixon_datastore.h
+++ b/lib/clixon/clixon_datastore.h
@@ -52,7 +52,7 @@ int xmldb_disconnect(clicon_handle h);
  /* in clixon_datastore_read.[ch] */
 int xmldb_get(clicon_handle h, const char *db, cvec *nsc, char *xpath, cxobj **xtop);
 int xmldb_get0(clicon_handle h, const char *db,
-	       cvec *nsc, char *xpath,
+	       cvec *nsc, const char *xpath,
 	       int copy, cxobj **xtop, modstate_diff_t *msd); 
 int xmldb_get0_clear(clicon_handle h, cxobj *x);
 int xmldb_get0_free(clicon_handle h, cxobj **xp);
diff --git a/lib/clixon/clixon_err.h b/lib/clixon/clixon_err.h
index 16a9a010..4e58eeb7 100644
--- a/lib/clixon/clixon_err.h
+++ b/lib/clixon/clixon_err.h
@@ -94,9 +94,9 @@ extern char clicon_err_reason[ERR_STRLEN];
  */
 int clicon_err_reset(void);
 #if defined(__GNUC__) && __GNUC__ >= 3
-int clicon_err_fn(const char *fn, const int line, int category, int err, char *format, ...) __attribute__ ((format (printf, 5, 6)));
+int clicon_err_fn(const char *fn, const int line, int category, int err, const char *format, ...) __attribute__ ((format (printf, 5, 6)));
 #else
-int clicon_err_fn(const char *fn, const int line, int category, int err, char *format, ...);
+int clicon_err_fn(const char *fn, const int line, int category, int err, const char *format, ...);
 #endif
 char *clicon_strerror(int err);
 void *clicon_err_save(void);
diff --git a/lib/clixon/clixon_log.h b/lib/clixon/clixon_log.h
index 21d87b5b..53b2cfe2 100644
--- a/lib/clixon/clixon_log.h
+++ b/lib/clixon/clixon_log.h
@@ -55,11 +55,11 @@ int clicon_log_opt(char c);
 int clicon_log_file(char *filename);
 int clicon_get_logflags(void);
 #if defined(__GNUC__) && __GNUC__ >= 3
-int clicon_log(int level, char *format, ...) __attribute__ ((format (printf, 2, 3)));
-int clicon_debug(int dbglevel, char *format, ...) __attribute__ ((format (printf, 2, 3)));
+int clicon_log(int level, const char *format, ...) __attribute__ ((format (printf, 2, 3)));
+int clicon_debug(int dbglevel, const char *format, ...) __attribute__ ((format (printf, 2, 3)));
 #else
-int clicon_log(int level, char *format, ...);
-int clicon_debug(int dbglevel, char *format, ...);
+int clicon_log(int level, const char *format, ...);
+int clicon_debug(int dbglevel, const char *format, ...);
 #endif
 int clicon_debug_init(int dbglevel, FILE *f);
 int clicon_debug_get(void);
diff --git a/lib/clixon/clixon_options.h b/lib/clixon/clixon_options.h
index 9628d9f2..03a5d2c6 100644
--- a/lib/clixon/clixon_options.h
+++ b/lib/clixon/clixon_options.h
@@ -125,7 +125,7 @@ enum regexp_mode{
 int clicon_option_dump(clicon_handle h, int dblevel);
 
 /* Add a clicon options overriding file setting */
-int clicon_option_add(clicon_handle h,	char *name, char *value);
+int clicon_option_add(clicon_handle h, const char *name, char *value);
 
 /* Initialize options: set defaults, read config-file, etc */
 int clicon_options_main(clicon_handle h);
diff --git a/lib/clixon/clixon_path.h b/lib/clixon/clixon_path.h
index ea665af2..08b717fc 100644
--- a/lib/clixon/clixon_path.h
+++ b/lib/clixon/clixon_path.h
@@ -85,13 +85,13 @@ int api_path2xml(char *api_path, yang_stmt *yspec, cxobj *xtop,
 		 cxobj **xpathp, yang_stmt **ypathp, cxobj **xerr);
 int xml2api_path_1(cxobj *x, cbuf *cb);
 #if defined(__GNUC__) && __GNUC__ >= 3
-int clixon_xml_find_api_path(cxobj *xt, yang_stmt *yt, cxobj ***xvec, int *xlen, char *format,
+int clixon_xml_find_api_path(cxobj *xt, yang_stmt *yt, cxobj ***xvec, int *xlen, const char *format,
 		     ...) __attribute__ ((format (printf, 5, 6)));;
-int clixon_xml_find_instance_id(cxobj *xt, yang_stmt *yt, cxobj ***xvec, int *xlen, char *format,
+int clixon_xml_find_instance_id(cxobj *xt, yang_stmt *yt, cxobj ***xvec, int *xlen, const char *format,
 		     ...) __attribute__ ((format (printf, 5, 6)));;
 #else
-int clixon_xml_find_api_path(cxobj *xt, yang_stmt *yt,  cxobj ***xvec, int *xlen, char *format, ...);
-int clixon_xml_find_instance_id(cxobj *xt, yang_stmt *yt, cxobj ***xvec, int *xlen, char *format, ...);
+int clixon_xml_find_api_path(cxobj *xt, yang_stmt *yt,  cxobj ***xvec, int *xlen, const char *format, ...);
+int clixon_xml_find_instance_id(cxobj *xt, yang_stmt *yt, cxobj ***xvec, int *xlen, const char *format, ...);
 #endif
 
 #endif  /* _CLIXON_PATH_H_ */
diff --git a/lib/clixon/clixon_plugin.h b/lib/clixon/clixon_plugin.h
index a3a29412..2873553d 100644
--- a/lib/clixon/clixon_plugin.h
+++ b/lib/clixon/clixon_plugin.h
@@ -179,7 +179,7 @@ typedef char *(cli_prompthook_t)(clicon_handle, char *mode);
  * @retval   -1    Error
  * @retval    0    OK
  */
-typedef int (datastore_upgrade_t)(clicon_handle h, char *db, cxobj *xt, modstate_diff_t *msd);
+typedef int (datastore_upgrade_t)(clicon_handle h, const char *db, cxobj *xt, modstate_diff_t *msd);
 
 /*! Startup status for use in startup-callback
  * Note that for STARTUP_ERR and _INVALID, running runs in failsafe mode
@@ -284,11 +284,11 @@ clixon_plugin *clixon_plugin_each(clicon_handle h, clixon_plugin *cpprev);
 
 clixon_plugin *clixon_plugin_each_revert(clicon_handle h, clixon_plugin *cpprev, int nr);
 
-clixon_plugin *clixon_plugin_find(clicon_handle h, char *name);
+clixon_plugin *clixon_plugin_find(clicon_handle h, const char *name);
 
-int clixon_plugins_load(clicon_handle h, char *function, char *dir, char *regexp);
+int clixon_plugins_load(clicon_handle h, const char *function, const char *dir, const char *regexp);
 
-int clixon_pseudo_plugin(clicon_handle h, char *name, clixon_plugin **cpp);
+int clixon_pseudo_plugin(clicon_handle h, const char *name, clixon_plugin **cpp);
 
 int clixon_plugin_start_one(clixon_plugin *cp, clicon_handle h);
 int clixon_plugin_start_all(clicon_handle h);
@@ -302,16 +302,16 @@ int clixon_plugin_auth_all(clicon_handle h, void *arg);
 int clixon_plugin_extension_one(clixon_plugin *cp, clicon_handle h, yang_stmt *yext, yang_stmt *ys);
 int clixon_plugin_extension_all(clicon_handle h, yang_stmt *yext, yang_stmt *ys);
 
-int clixon_plugin_datastore_upgrade_one(clixon_plugin *cp, clicon_handle h, char *db, cxobj *xt, modstate_diff_t *msd);
-int clixon_plugin_datastore_upgrade_all(clicon_handle h, char *db, cxobj *xt, modstate_diff_t *msd);
+int clixon_plugin_datastore_upgrade_one(clixon_plugin *cp, clicon_handle h, const char *db, cxobj *xt, modstate_diff_t *msd);
+int clixon_plugin_datastore_upgrade_all(clicon_handle h, const char *db, cxobj *xt, modstate_diff_t *msd);
 
 /* rpc callback API */
-int rpc_callback_register(clicon_handle h, clicon_rpc_cb cb, void *arg, char *ns, char *name);
+int rpc_callback_register(clicon_handle h, clicon_rpc_cb cb, void *arg, const char *ns, const char *name);
 int rpc_callback_delete_all(clicon_handle h);
 int rpc_callback_call(clicon_handle h, cxobj *xe, cbuf *cbret, void *arg);
 
 /* upgrade callback API */
-int upgrade_callback_reg_fn(clicon_handle h, clicon_upgrade_cb cb, const char *strfn, char *ns, void *arg);
+int upgrade_callback_reg_fn(clicon_handle h, clicon_upgrade_cb cb, const char *strfn, const char *ns, void *arg);
 int upgrade_callback_delete_all(clicon_handle h);
 int upgrade_callback_call(clicon_handle h, cxobj *xt, char *ns, uint16_t op, uint32_t from, uint32_t to, cbuf *cbret);
 
diff --git a/lib/clixon/clixon_proto.h b/lib/clixon/clixon_proto.h
index bb91f4d3..2d08a7ef 100644
--- a/lib/clixon/clixon_proto.h
+++ b/lib/clixon/clixon_proto.h
@@ -2,7 +2,9 @@
  *
   ***** BEGIN LICENSE BLOCK *****
  
-  Copyright (C) 2009-2019 Olof Hagsand and Benny Holmgren
+  Copyright (C) 2009-2016 Olof Hagsand and Benny Holmgren
+  Copyright (C) 2017-2019 Olof Hagsand
+  Copyright (C) 2020 Olof Hagsand and Rubicon Communications, LLC(Netgate)
 
   This file is part of CLIXON.
 
@@ -63,9 +65,9 @@ char *format_int2str(enum format_enum showas);
 enum format_enum format_str2int(char *str);
 
 #if defined(__GNUC__) && __GNUC__ >= 3
-struct clicon_msg *clicon_msg_encode(uint32_t id, char *format, ...) __attribute__ ((format (printf, 2, 3)));
+struct clicon_msg *clicon_msg_encode(uint32_t id, const char *format, ...) __attribute__ ((format (printf, 2, 3)));
 #else
-struct clicon_msg *clicon_msg_encode(uint32_t id, char *format, ...);
+struct clicon_msg *clicon_msg_encode(uint32_t id, const char *format, ...);
 #endif
 int clicon_msg_decode(struct clicon_msg *msg, yang_stmt *yspec, uint32_t *id, cxobj **xml, cxobj **xerr);
 
diff --git a/lib/clixon/clixon_string.h b/lib/clixon/clixon_string.h
index 9613ecf4..c35c2e5a 100644
--- a/lib/clixon/clixon_string.h
+++ b/lib/clixon/clixon_string.h
@@ -92,11 +92,11 @@ char *clicon_strjoin (int argc, char **argv, char *delim);
 int clixon_strsplit(char *nodeid, const int delim, char **prefix, char **id);
 int str2cvec(char *string, char delim1, char delim2, cvec **cvp);
 #if defined(__GNUC__) && __GNUC__ >= 3
-int uri_percent_encode(char **encp, char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
-int xml_chardata_encode(char **escp, char *fmt, ... ) __attribute__ ((format (printf, 2, 3)));
+int uri_percent_encode(char **encp, const char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
+int xml_chardata_encode(char **escp, const char *fmt, ... ) __attribute__ ((format (printf, 2, 3)));
 #else
-int uri_percent_encode(char **encp, char *str, ...);
-int xml_chardata_encode(char **escp, char *fmt, ...);
+int uri_percent_encode(char **encp, const char *str, ...);
+int xml_chardata_encode(char **escp, const char *fmt, ...);
 #endif
 int xml_chardata_cbuf_append(cbuf *cb, char *str);
 int uri_percent_decode(char *enc, char **str);
diff --git a/lib/clixon/clixon_xml.h b/lib/clixon/clixon_xml.h
index 822a6d35..685b0eb9 100644
--- a/lib/clixon/clixon_xml.h
+++ b/lib/clixon/clixon_xml.h
@@ -213,12 +213,12 @@ int       xml_enumerate_get(cxobj *x);
 
 char     *xml_body(cxobj *xn);
 cxobj    *xml_body_get(cxobj *xn);
-char     *xml_find_type_value(cxobj *xn_parent, char *prefix,
-			      char *name, enum cxobj_type type);
-cxobj    *xml_find_type(cxobj *xn_parent, char *prefix, char *name, enum cxobj_type type);
-char     *xml_find_value(cxobj *xn_parent, char *name);
-char     *xml_find_body(cxobj *xn, char *name);
-cxobj    *xml_find_body_obj(cxobj *xt, char *name, char *val);
+char     *xml_find_type_value(cxobj *xn_parent, const char *prefix,
+			      const char *name, enum cxobj_type type);
+cxobj    *xml_find_type(cxobj *xn_parent, const char *prefix, const char *name, enum cxobj_type type);
+char     *xml_find_value(cxobj *xn_parent, const char *name);
+char     *xml_find_body(cxobj *xn, const char *name);
+cxobj    *xml_find_body_obj(cxobj *xt, const char *name, char *val);
 
 int       xml_free(cxobj *xn);
 
@@ -239,9 +239,9 @@ int       xml_operation(char *opstr, enum operation_type *op);
 char     *xml_operation2str(enum operation_type op);
 int       xml_attr_insert2val(char *instr, enum insert_type *ins);
 #if defined(__GNUC__) && __GNUC__ >= 3
-int       clicon_log_xml(int level, cxobj *x, char *format, ...)  __attribute__ ((format (printf, 3, 4)));
+int       clicon_log_xml(int level, cxobj *x, const char *format, ...)  __attribute__ ((format (printf, 3, 4)));
 #else
-int       clicon_log_xml(int level, cxobj *x, char *format, ...);
+int       clicon_log_xml(int level, cxobj *x, const char *format, ...);
 #endif
 #ifdef XML_EXPLICIT_INDEX
 int       xml_search_index_p(cxobj *x);
diff --git a/lib/clixon/clixon_xpath.h b/lib/clixon/clixon_xpath.h
index 02594837..f842de4d 100644
--- a/lib/clixon/clixon_xpath.h
+++ b/lib/clixon/clixon_xpath.h
@@ -129,17 +129,17 @@ int   xpath_tree2cbuf(xpath_tree *xs, cbuf *xpathcb);
 int   xpath_tree_eq(xpath_tree *xt1, xpath_tree *xt2, xpath_tree ***vec, size_t *len);
 xpath_tree *xpath_tree_traverse(xpath_tree *xt, ...);
 int   xpath_tree_free(xpath_tree *xs);
-int   xpath_parse(char *xpath, xpath_tree **xptree);
-int   xpath_vec_ctx(cxobj *xcur, cvec *nsc, char *xpath, int localonly, xp_ctx  **xrp);
+int   xpath_parse(const char *xpath, xpath_tree **xptree);
+int   xpath_vec_ctx(cxobj *xcur, cvec *nsc, const char *xpath, int localonly, xp_ctx  **xrp);
 
 #if defined(__GNUC__) && __GNUC__ >= 3
-int    xpath_vec_bool(cxobj *xcur, cvec *nsc, char *xpformat, ...) __attribute__ ((format (printf, 3, 4)));
-int    xpath_vec_flag(cxobj *xcur, cvec *nsc, char *xpformat, uint16_t flags, 
+int    xpath_vec_bool(cxobj *xcur, cvec *nsc, const char *xpformat, ...) __attribute__ ((format (printf, 3, 4)));
+int    xpath_vec_flag(cxobj *xcur, cvec *nsc, const char *xpformat, uint16_t flags, 
 		   cxobj ***vec, int *veclen, ...) __attribute__ ((format (printf, 3, 7)));
 
 #else
-int    xpath_vec_bool(cxobj *xcur, cvec *nsc, char *xpformat, ...);
-int    xpath_vec_flag(cxobj *xcur, cvec *nsc, char *xpformat, uint16_t flags, 
+int    xpath_vec_bool(cxobj *xcur, cvec *nsc, const char *xpformat, ...);
+int    xpath_vec_flag(cxobj *xcur, cvec *nsc, const char *xpformat, uint16_t flags, 
 		      cxobj ***vec, int *veclen, ...);
 #endif
 
@@ -149,15 +149,15 @@ int    xpath_vec_flag(cxobj *xcur, cvec *nsc, char *xpformat, uint16_t flags,
  * If you do not know what a namespace context is, see README.md#xml-and-xpath
  */
 #if defined(__GNUC__) && __GNUC__ >= 3
-cxobj *xpath_first(cxobj *xcur, cvec *nsc, char *xpformat,  ...) __attribute__ ((format (printf, 3, 4)));
-cxobj *xpath_first_localonly(cxobj *xcur, char *xpformat,  ...) __attribute__ ((format (printf, 2, 3)));
-int    xpath_vec(cxobj *xcur, cvec *nsc, char *xpformat, cxobj ***vec, size_t *veclen, ...) __attribute__ ((format (printf, 3, 6)));
+cxobj *xpath_first(cxobj *xcur, cvec *nsc, const char *xpformat,  ...) __attribute__ ((format (printf, 3, 4)));
+cxobj *xpath_first_localonly(cxobj *xcur, const char *xpformat,  ...) __attribute__ ((format (printf, 2, 3)));
+int    xpath_vec(cxobj *xcur, cvec *nsc, const char *xpformat, cxobj ***vec, size_t *veclen, ...) __attribute__ ((format (printf, 3, 6)));
 #else
-cxobj *xpath_first(cxobj *xcur, cvec *nsc, char *xpformat, ...);
-cxobj *xpath_first_localonly(cxobj *xcur, char *xpformat, ...);
-int    xpath_vec(cxobj *xcur, cvec *nsc, char *xpformat, cxobj  ***vec, size_t *veclen, ...);
+cxobj *xpath_first(cxobj *xcur, cvec *nsc, const char *xpformat, ...);
+cxobj *xpath_first_localonly(cxobj *xcur, const char *xpformat, ...);
+int    xpath_vec(cxobj *xcur, cvec *nsc, const char *xpformat, cxobj  ***vec, size_t *veclen, ...);
 #endif
 
-int xpath2canonical(char *xpath0, cvec *nsc0, yang_stmt *yspec, char **xpath1, cvec **nsc1);
+int xpath2canonical(const char *xpath0, cvec *nsc0, yang_stmt *yspec, char **xpath1, cvec **nsc1);
 
 #endif /* _CLIXON_XPATH_H */
diff --git a/lib/src/clixon_data.c b/lib/src/clixon_data.c
index fe6aaaaf..325079da 100644
--- a/lib/src/clixon_data.c
+++ b/lib/src/clixon_data.c
@@ -88,7 +88,7 @@
  */
 int
 clicon_data_get(clicon_handle h,
-		char         *name,
+		const char   *name,
 		char        **val)
 {
     clicon_hash_t *cdat = clicon_data(h);
@@ -110,7 +110,7 @@ clicon_data_get(clicon_handle h,
  */
 int
 clicon_data_set(clicon_handle h, 
-		char         *name,
+		const char   *name,
 		char         *val)
 {
     clicon_hash_t  *cdat = clicon_data(h);
@@ -127,7 +127,7 @@ clicon_data_set(clicon_handle h,
  */
 int
 clicon_data_del(clicon_handle h, 
-		char         *name)
+		const char   *name)
 {
     clicon_hash_t  *cdat = clicon_data(h);
 
diff --git a/lib/src/clixon_datastore_read.c b/lib/src/clixon_datastore_read.c
index 2df896d6..d52752c0 100644
--- a/lib/src/clixon_datastore_read.c
+++ b/lib/src/clixon_datastore_read.c
@@ -427,7 +427,7 @@ static int
 xmldb_get_nocache(clicon_handle       h,
 		  const char         *db, 
 		  cvec               *nsc,
-		  char               *xpath,
+		  const char         *xpath,
 		  cxobj             **xtop,
 		  modstate_diff_t    *msdiff)
 {
@@ -511,7 +511,7 @@ static int
 xmldb_get_cache(clicon_handle    h,
 		const char      *db, 
 		cvec            *nsc,
-		char            *xpath,
+		const char      *xpath,
 		cxobj          **xtop,
 		modstate_diff_t *msdiff)
 {
@@ -612,7 +612,7 @@ static int
 xmldb_get_zerocopy(clicon_handle    h,
 		   const char      *db, 
 		   cvec            *nsc,
-		   char            *xpath,
+		   const char      *xpath,
 		   cxobj          **xtop,
 		   modstate_diff_t *msdiff)
 {
@@ -726,7 +726,7 @@ int
 xmldb_get0(clicon_handle    h, 
 	   const char      *db, 
 	   cvec            *nsc,
-	   char            *xpath,
+	   const char      *xpath,
 	   int              copy,
 	   cxobj          **xret,
 	   modstate_diff_t *msdiff)
diff --git a/lib/src/clixon_err.c b/lib/src/clixon_err.c
index a99bdc0a..d0901900 100644
--- a/lib/src/clixon_err.c
+++ b/lib/src/clixon_err.c
@@ -149,7 +149,7 @@ int clicon_err_fn(const char *fn,
 		  const int  line,
 		  int        category,
 		  int        suberr,
-		  char      *format, ...) 
+		  const char *format, ...) 
 {
     va_list args;
     int     len;
diff --git a/lib/src/clixon_log.c b/lib/src/clixon_log.c
index c3a752e0..793ac5d7 100644
--- a/lib/src/clixon_log.c
+++ b/lib/src/clixon_log.c
@@ -257,8 +257,8 @@ clicon_log_str(int           level,
  * @see clicon_log_init and clicon_log_str
  */
 int
-clicon_log(int   level, 
-	   char *format, ...)
+clicon_log(int         level, 
+	   const char *format, ...)
 {
     va_list args;
     int     len;
@@ -338,8 +338,8 @@ clicon_debug_get(void)
  * @param[in] format     Message to print as argv.
  */
 int
-clicon_debug(int   dbglevel, 
-	     char *format, ...)
+clicon_debug(int         dbglevel, 
+	     const char *format, ...)
 {
     va_list args;
     int     len;
diff --git a/lib/src/clixon_options.c b/lib/src/clixon_options.c
index 8e69ad4a..0380f26b 100644
--- a/lib/src/clixon_options.c
+++ b/lib/src/clixon_options.c
@@ -327,7 +327,7 @@ parse_configfile(clicon_handle  h,
  */
 int
 clicon_option_add(clicon_handle h,
-		  char         *name,
+		  const char   *name,
 		  char         *value)
 {
     int            retval = -1;
diff --git a/lib/src/clixon_path.c b/lib/src/clixon_path.c
index ff17384c..b1aaa671 100644
--- a/lib/src/clixon_path.c
+++ b/lib/src/clixon_path.c
@@ -1529,7 +1529,7 @@ clixon_xml_find_api_path(cxobj        *xt,
 			 yang_stmt    *yt,
 			 cxobj      ***xvec,
 			 int          *xlen,
-			 char         *format,
+			 const char   *format,
 			 ...)
 {
     int              retval = -1;
@@ -1623,7 +1623,7 @@ clixon_xml_find_instance_id(cxobj     *xt,
 			    yang_stmt *yt,
 			    cxobj   ***xvec,
 			    int       *xlen,
-			    char      *format,
+			    const char *format,
 			    ...)
 {
     int          retval = -1;
diff --git a/lib/src/clixon_plugin.c b/lib/src/clixon_plugin.c
index 13d24b83..dabbb935 100644
--- a/lib/src/clixon_plugin.c
+++ b/lib/src/clixon_plugin.c
@@ -159,7 +159,7 @@ clixon_plugin_each_revert(clicon_handle  h,
  */
 clixon_plugin *
 clixon_plugin_find(clicon_handle h,
-		   char         *name)
+		   const char   *name)
 {
     int            i;
     clixon_plugin *cp = NULL;
@@ -185,8 +185,8 @@ clixon_plugin_find(clicon_handle h,
  */
 static int
 plugin_load_one(clicon_handle   h, 
-		char           *file,
-		char           *function,
+		char           *file, /* note modified */
+		const char     *function,
 		int             dlflags,
 		clixon_plugin **cpp)
 {
@@ -267,9 +267,9 @@ plugin_load_one(clicon_handle   h,
  */
 int
 clixon_plugins_load(clicon_handle h,
-    		    char         *function,
-		    char         *dir,
-    		    char         *regexp)
+    		    const char   *function,
+		    const char   *dir,
+    		    const char   *regexp)
 {
     int            retval = -1;
     int            ndp;
@@ -316,7 +316,7 @@ done:
  */
 int
 clixon_pseudo_plugin(clicon_handle   h,
-		     char           *name,
+		     const char     *name,
 		     clixon_plugin **cpp)
 {
     int            retval = -1;
@@ -595,7 +595,7 @@ clixon_plugin_extension_all(clicon_handle h,
 int
 clixon_plugin_datastore_upgrade_one(clixon_plugin   *cp,
 				    clicon_handle    h,
-				    char            *db,
+				    const char      *db,
 				    cxobj           *xt,
 				    modstate_diff_t *msd)
 
@@ -628,7 +628,7 @@ clixon_plugin_datastore_upgrade_one(clixon_plugin   *cp,
  */
 int
 clixon_plugin_datastore_upgrade_all(clicon_handle    h,
-				    char            *db,
+				    const char      *db,
 				    cxobj           *xt,
 				    modstate_diff_t *msd)
 {
@@ -682,8 +682,8 @@ int
 rpc_callback_register(clicon_handle  h,
 		      clicon_rpc_cb  cb,
 		      void          *arg,       
-    		      char          *ns,
-		      char          *name)
+    		      const char    *ns,
+		      const char    *name)
 {
     rpc_callback_t *rc = NULL;
 
@@ -813,7 +813,7 @@ int
 upgrade_callback_reg_fn(clicon_handle     h,
 			clicon_upgrade_cb cb,
 			const char       *fnstr,
-			char             *ns,
+			const char       *ns,
 			void             *arg)
 {
     upgrade_callback_t *uc;
diff --git a/lib/src/clixon_proto.c b/lib/src/clixon_proto.c
index 84082877..71aceb63 100644
--- a/lib/src/clixon_proto.c
+++ b/lib/src/clixon_proto.c
@@ -136,7 +136,7 @@ format_str2int(char *str)
  */
 struct clicon_msg *
 clicon_msg_encode(uint32_t      id,
-		  char         *format, ...)
+		  const char   *format, ...)
 {
     va_list            args;
     uint32_t           xmllen;
diff --git a/lib/src/clixon_string.c b/lib/src/clixon_string.c
index 4bf9b021..66d8d563 100644
--- a/lib/src/clixon_string.c
+++ b/lib/src/clixon_string.c
@@ -244,7 +244,7 @@ uri_unreserved(unsigned char in)
  */
 int
 uri_percent_encode(char **encp, 
-		   char  *fmt, ...)
+		   const char *fmt, ...)
 {
     int     retval = -1;
     char   *str = NULL;  /* Expanded format string w stdarg */
@@ -370,8 +370,8 @@ uri_percent_decode(char  *enc,
  * @see xml_chardata_cbuf_append for a specialized version
  */
 int
-xml_chardata_encode(char **escp,
-		    char  *fmt,...)
+xml_chardata_encode(char      **escp,
+		    const char *fmt,...)
 {
     int     retval = -1;
     char   *str = NULL;  /* Expanded format string w stdarg */
diff --git a/lib/src/clixon_xml.c b/lib/src/clixon_xml.c
index d7915da0..712b32d0 100644
--- a/lib/src/clixon_xml.c
+++ b/lib/src/clixon_xml.c
@@ -1661,8 +1661,8 @@ xml_body_get(cxobj *xt)
  */
 char *
 xml_find_type_value(cxobj           *xt, 
-		    char            *prefix,
-		    char            *name,
+		    const char      *prefix,
+		    const char      *name,
 		    enum cxobj_type  type)
 {
     cxobj *x;
@@ -1691,8 +1691,8 @@ xml_find_type_value(cxobj           *xt,
  */
 cxobj *
 xml_find_type(cxobj           *xt, 
-	      char            *prefix,
-	      char            *name,
+	      const char      *prefix,
+	      const char      *name,
 	      enum cxobj_type  type)
 {
     cxobj *x = NULL;
@@ -1730,8 +1730,8 @@ xml_find_type(cxobj           *xt,
  *               return x_value
  */
 char *
-xml_find_value(cxobj *xt, 
-	       char  *name)
+xml_find_value(cxobj      *xt, 
+	       const char *name)
 {
     cxobj *x = NULL;
     
@@ -1755,8 +1755,8 @@ xml_find_value(cxobj *xt,
  *               x_name=name    return x_value
  */
 char *
-xml_find_body(cxobj *xt, 
-	      char  *name)
+xml_find_body(cxobj      *xt, 
+	      const char *name)
 {
     cxobj *x=NULL;
 
@@ -1783,9 +1783,9 @@ xml_find_body(cxobj *xt,
  *               return x
  */
 cxobj *
-xml_find_body_obj(cxobj *xt, 
-		  char  *name,
-		  char  *val)
+xml_find_body_obj(cxobj      *xt, 
+		  const char *name,
+		  char       *val)
 {
     cxobj *x = NULL;
     char  *bstr;
@@ -2315,9 +2315,9 @@ xml_attr_insert2val(char             *instr,
  * @param[in]  format   Message to print as argv.
 */
 int
-clicon_log_xml(int    level, 
-	       cxobj *x,
-	       char  *format, ...)
+clicon_log_xml(int         level, 
+	       cxobj      *x,
+	       const char *format, ...)
 {
     va_list args;
     int     len;
diff --git a/lib/src/clixon_xpath.c b/lib/src/clixon_xpath.c
index 70a72361..15bf7260 100644
--- a/lib/src/clixon_xpath.c
+++ b/lib/src/clixon_xpath.c
@@ -483,7 +483,7 @@ xpath_tree_free(xpath_tree *xs)
  * @see xpath_tree_free 
  */
 int
-xpath_parse(char        *xpath,
+xpath_parse(const char  *xpath,
 	    xpath_tree **xptree)
 {
     int               retval = -1;
@@ -541,11 +541,11 @@ xpath_parse(char        *xpath,
  * @endcode
  */
 int
-xpath_vec_ctx(cxobj    *xcur, 
-	      cvec     *nsc,
-	      char     *xpath,
-	      int       localonly,
-	      xp_ctx  **xrp)
+xpath_vec_ctx(cxobj      *xcur, 
+	      cvec       *nsc,
+	      const char *xpath,
+	      int         localonly,
+	      xp_ctx    **xrp)
 {
     int         retval = -1;
     xpath_tree *xptree = NULL;
@@ -591,9 +591,9 @@ xpath_vec_ctx(cxobj    *xcur,
  * @see also xpath_vec.
  */
 cxobj *
-xpath_first(cxobj    *xcur, 
-	    cvec     *nsc,
-	    char     *xpformat, 
+xpath_first(cxobj      *xcur, 
+	    cvec       *nsc,
+	    const char *xpformat, 
 	    ...)
 {
     cxobj     *cx = NULL;
@@ -651,8 +651,8 @@ xpath_first(cxobj    *xcur,
  * @see also xpath_first.
  */
 cxobj *
-xpath_first_localonly(cxobj    *xcur, 
-		      char     *xpformat, 
+xpath_first_localonly(cxobj      *xcur, 
+		      const char *xpformat, 
 		      ...)
 {
     cxobj     *cx = NULL;
@@ -712,11 +712,11 @@ xpath_first_localonly(cxobj    *xcur,
  * @endcode
  */
 int
-xpath_vec(cxobj    *xcur, 
-	  cvec     *nsc,
-	  char     *xpformat, 
-	  cxobj  ***vec, 
-	  size_t   *veclen,
+xpath_vec(cxobj      *xcur, 
+	  cvec       *nsc,
+	  const char *xpformat, 
+	  cxobj    ***vec, 
+	  size_t     *veclen,
 	  ...)
 {
     int        retval = -1;
@@ -784,12 +784,12 @@ xpath_vec(cxobj    *xcur,
  * @see also xpath_vec  This is a specialized version.
  */
 int
-xpath_vec_flag(cxobj    *xcur, 
-	       cvec     *nsc,
-	       char     *xpformat, 
-	       uint16_t  flags,
-	       cxobj  ***vec, 
-	       int      *veclen,
+xpath_vec_flag(cxobj      *xcur, 
+	       cvec       *nsc,
+	       const char *xpformat, 
+	       uint16_t    flags,
+	       cxobj    ***vec, 
+	       int        *veclen,
 	       ...)
 {
     int        retval = -1;
@@ -847,9 +847,9 @@ xpath_vec_flag(cxobj    *xcur,
  * @retval    -1        Error
  */
 int
-xpath_vec_bool(cxobj *xcur, 
-	       cvec  *nsc,
-	       char  *xpformat, 
+xpath_vec_bool(cxobj      *xcur, 
+	       cvec       *nsc,
+	       const char *xpformat, 
 	       ...)
 {
     int        retval = -1;
@@ -970,7 +970,7 @@ traverse_canonical(xpath_tree *xs,
  * @endcode
  */
 int
-xpath2canonical(char      *xpath0,
+xpath2canonical(const char *xpath0,
 		cvec      *nsc0,
 		yang_stmt *yspec,
 		char     **xpath1,
diff --git a/lib/src/clixon_xpath_parse.h b/lib/src/clixon_xpath_parse.h
index 8fa28d0f..cb29133d 100644
--- a/lib/src/clixon_xpath_parse.h
+++ b/lib/src/clixon_xpath_parse.h
@@ -43,7 +43,7 @@
 struct clixon_xpath_yacc{ 
     const char           *xpy_name;         /* Name of syntax (for error string) */
     int                   xpy_linenum;      /* Number of \n in parsed buffer */
-    char                 *xpy_parse_string; /* original (copy of) parse string */
+    const char           *xpy_parse_string; /* original (copy of) parse string */
     void                 *xpy_lexbuf;       /* internal parse buffer from lex */
     xpath_tree           *xpy_top;
 };
diff --git a/test/test_c++.sh b/test/test_c++.sh
index df6c141a..248e3a89 100755
--- a/test/test_c++.sh
+++ b/test/test_c++.sh
@@ -50,7 +50,7 @@ netconf_client_rpc(clicon_handle h,
     char  *ns;
 
     /* get namespace from rpc name, return back in each output parameter */
-    if ((ns = xml_find_type_value(xe, NULL, (char*)"xmlns", CX_ATTR)) == NULL){
+    if ((ns = xml_find_type_value(xe, NULL, "xmlns", CX_ATTR)) == NULL){
 	clicon_err(OE_XML, ENOENT, "No namespace given in rpc %s", xml_name(xe));
 	goto done;
     }
@@ -94,10 +94,10 @@ clixon_plugin_init(clicon_handle h)
 
 	api_initialization();
 
-    clicon_debug(1, (char*)"%s netconf", __FUNCTION__);
+    clicon_debug(1, "%s netconf", __FUNCTION__);
     /* Register local netconf rpc client (note not backend rpc client) */
     if (rpc_callback_register(h, netconf_client_rpc, NULL,
-			      (char*)"urn:example:clixon", (char*)"client-rpc") < 0)
+			      "urn:example:clixon", "client-rpc") < 0)
 	return NULL;
     return &api;
 }