diff --git a/src/engine-assuan.c b/src/engine-assuan.c
index 1f48173f..5f0ea06d 100644
--- a/src/engine-assuan.c
+++ b/src/engine-assuan.c
@@ -359,7 +359,7 @@ llass_set_locale (void *engine, int category, const char *value)
   gpgme_error_t err;
   engine_llass_t llass = engine;
   char *optstr;
-  char *catstr;
+  const char *catstr;
 
   if (!llass->opt.gpg_agent)
     return 0;
diff --git a/src/engine-g13.c b/src/engine-g13.c
index ce98b1bd..7f225eb2 100644
--- a/src/engine-g13.c
+++ b/src/engine-g13.c
@@ -356,7 +356,7 @@ g13_set_locale (void *engine, int category, const char *value)
   engine_g13_t g13 = engine;
   gpgme_error_t err;
   char *optstr;
-  char *catstr;
+  const char *catstr;
 
   /* FIXME: If value is NULL, we need to reset the option to default.
      But we can't do this.  So we error out here.  G13 needs support
@@ -405,7 +405,7 @@ g13_set_locale (void *engine, int category, const char *value)
 
 #if USE_DESCRIPTOR_PASSING
 static gpgme_error_t
-g13_assuan_simple_command (assuan_context_t ctx, char *cmd,
+g13_assuan_simple_command (assuan_context_t ctx, const char *cmd,
 			   engine_status_handler_t status_fnc,
 			   void *status_fnc_value)
 {
diff --git a/src/engine-gpg.c b/src/engine-gpg.c
index 7270e362..f22d8b44 100644
--- a/src/engine-gpg.c
+++ b/src/engine-gpg.c
@@ -1574,6 +1574,8 @@ gpg_passwd (void *engine, gpgme_key_t key, unsigned int flags)
   engine_gpg_t gpg = engine;
   gpgme_error_t err;
 
+  (void)flags;
+
   if (!key || !key->subkeys || !key->subkeys->fpr)
     return gpg_error (GPG_ERR_INV_CERT_OBJ);
 
diff --git a/src/engine-gpgsm.c b/src/engine-gpgsm.c
index 1cf50467..0610c7a7 100644
--- a/src/engine-gpgsm.c
+++ b/src/engine-gpgsm.c
@@ -517,7 +517,7 @@ gpgsm_set_locale (void *engine, int category, const char *value)
   engine_gpgsm_t gpgsm = engine;
   gpgme_error_t err;
   char *optstr;
-  char *catstr;
+  const char *catstr;
 
   /* FIXME: If value is NULL, we need to reset the option to default.
      But we can't do this.  So we error out here.  GPGSM needs support
@@ -565,7 +565,7 @@ gpgsm_set_locale (void *engine, int category, const char *value)
 
 
 static gpgme_error_t
-gpgsm_assuan_simple_command (engine_gpgsm_t gpgsm, char *cmd,
+gpgsm_assuan_simple_command (engine_gpgsm_t gpgsm, const char *cmd,
 			     engine_status_handler_t status_fnc,
 			     void *status_fnc_value)
 {
@@ -674,7 +674,7 @@ gpgsm_set_fd (engine_gpgsm_t gpgsm, fd_type_t fd_type, const char *opt)
 {
   gpg_error_t err = 0;
   char line[COMMANDLINELEN];
-  char *which;
+  const char *which;
   iocb_data_t *iocb_data;
 #if USE_DESCRIPTOR_PASSING
   int dir;
@@ -1480,6 +1480,7 @@ gpgsm_genkey (void *engine,
     }
 
   (void)userid;
+  (void)algo;
   (void)expires;
   (void)key;
   (void)flags;
@@ -2017,6 +2018,8 @@ gpgsm_passwd (void *engine, gpgme_key_t key, unsigned int flags)
   gpgme_error_t err;
   char *line;
 
+  (void)flags;
+
   if (!key || !key->subkeys || !key->subkeys->fpr)
     return gpg_error (GPG_ERR_INV_CERT_OBJ);
 
diff --git a/src/engine-uiserver.c b/src/engine-uiserver.c
index 215dbe39..2817527f 100644
--- a/src/engine-uiserver.c
+++ b/src/engine-uiserver.c
@@ -251,6 +251,7 @@ uiserver_new (void **engine, const char *file_name, const char *home_dir,
   char *dft_ttytype = NULL;
   char *optstr;
 
+  (void)home_dir;
   (void)version; /* Not yet used.  */
 
   uiserver = calloc (1, sizeof *uiserver);
@@ -400,7 +401,7 @@ uiserver_set_locale (void *engine, int category, const char *value)
   engine_uiserver_t uiserver = engine;
   gpgme_error_t err;
   char *optstr;
-  char *catstr;
+  const char *catstr;
 
   /* FIXME: If value is NULL, we need to reset the option to default.
      But we can't do this.  So we error out here.  UISERVER needs support
@@ -459,7 +460,7 @@ uiserver_set_protocol (void *engine, gpgme_protocol_t protocol)
 
 
 static gpgme_error_t
-uiserver_assuan_simple_command (engine_uiserver_t uiserver, char *cmd,
+uiserver_assuan_simple_command (engine_uiserver_t uiserver, const char *cmd,
                                 engine_status_handler_t status_fnc,
                                 void *status_fnc_value)
 {
@@ -534,7 +535,7 @@ uiserver_set_fd (engine_uiserver_t uiserver, fd_type_t fd_type, const char *opt)
 {
   gpg_error_t err = 0;
   char line[COMMANDLINELEN];
-  char *which;
+  const char *which;
   iocb_data_t *iocb_data;
   int dir;
 
diff --git a/src/gpgme-tool.c b/src/gpgme-tool.c
index 80d7d725..fb158f13 100644
--- a/src/gpgme-tool.c
+++ b/src/gpgme-tool.c
@@ -202,7 +202,7 @@ peek_membuf (membuf_t *mb, size_t *len)
 
 /* SUPPORT.  */
 FILE *log_stream;
-char *program_name = "gpgme-tool";
+char program_name[] = "gpgme-tool";
 
 #define spacep(p)   (*(p) == ' ' || *(p) == '\t')
 
@@ -308,7 +308,7 @@ struct result_xml_state
 
 #define MAX_TAGS 20
   int next_tag;
-  char *tag[MAX_TAGS];
+  const char *tag[MAX_TAGS];
   int had_data[MAX_TAGS];
 };
 
@@ -492,7 +492,8 @@ result_xml_tag_end (struct result_xml_state *state)
 
 
 gpg_error_t
-result_add_error (struct result_xml_state *state, char *name, gpg_error_t err)
+result_add_error (struct result_xml_state *state,
+                  const char *name, gpg_error_t err)
 {
   char code[20];
   char msg[1024];
@@ -508,7 +509,7 @@ result_add_error (struct result_xml_state *state, char *name, gpg_error_t err)
 
 gpg_error_t
 result_add_pubkey_algo (struct result_xml_state *state,
-			char *name, gpgme_pubkey_algo_t algo)
+			const char *name, gpgme_pubkey_algo_t algo)
 {
   char code[20];
   char msg[80];
@@ -524,10 +525,11 @@ result_add_pubkey_algo (struct result_xml_state *state,
 
 gpg_error_t
 result_add_hash_algo (struct result_xml_state *state,
-			 char *name, gpgme_hash_algo_t algo)
+                      const char *name, gpgme_hash_algo_t algo)
 {
   char code[20];
   char msg[80];
+
   snprintf (code, sizeof (code) - 1, "0x%x", algo);
   snprintf (msg, sizeof (msg) - 1, "%s",
 	    gpgme_hash_algo_name (algo));
@@ -539,7 +541,8 @@ result_add_hash_algo (struct result_xml_state *state,
 
 
 gpg_error_t
-result_add_keyid (struct result_xml_state *state, char *name, char *keyid)
+result_add_keyid (struct result_xml_state *state,
+                  const char *name, const char *keyid)
 {
   result_xml_tag_start (state, name, NULL);
   result_xml_tag_data (state, keyid);
@@ -549,7 +552,8 @@ result_add_keyid (struct result_xml_state *state, char *name, char *keyid)
 
 
 gpg_error_t
-result_add_fpr (struct result_xml_state *state, char *name, char *fpr)
+result_add_fpr (struct result_xml_state *state,
+                const char *name, const char *fpr)
 {
   result_xml_tag_start (state, name, NULL);
   result_xml_tag_data (state, fpr);
@@ -559,7 +563,7 @@ result_add_fpr (struct result_xml_state *state, char *name, char *fpr)
 
 
 gpg_error_t
-result_add_timestamp (struct result_xml_state *state, char *name,
+result_add_timestamp (struct result_xml_state *state, const char *name,
 		      unsigned int timestamp)
 {
   char code[20];
@@ -572,10 +576,10 @@ result_add_timestamp (struct result_xml_state *state, char *name,
 
 
 gpg_error_t
-result_add_sig_mode (struct result_xml_state *state, char *name,
+result_add_sig_mode (struct result_xml_state *state, const char *name,
 		     gpgme_sig_mode_t sig_mode)
 {
-  char *mode;
+  const char *mode;
   char code[20];
 
   snprintf (code, sizeof (code) - 1, "%i", sig_mode);
@@ -602,7 +606,7 @@ result_add_sig_mode (struct result_xml_state *state, char *name,
 
 
 gpg_error_t
-result_add_protocol (struct result_xml_state *state, char *name,
+result_add_protocol (struct result_xml_state *state, const char *name,
 		     gpgme_protocol_t protocol)
 {
   const char *str;
@@ -620,7 +624,7 @@ result_add_protocol (struct result_xml_state *state, char *name,
 
 
 gpg_error_t
-result_add_validity (struct result_xml_state *state, char *name,
+result_add_validity (struct result_xml_state *state, const char *name,
 		     gpgme_validity_t validity)
 {
   const char *str;
@@ -657,7 +661,7 @@ result_add_validity (struct result_xml_state *state, char *name,
 
 gpg_error_t
 result_add_value (struct result_xml_state *state,
-		  char *name, unsigned int val)
+		  const char *name, unsigned int val)
 {
   char code[20];
 
@@ -670,7 +674,7 @@ result_add_value (struct result_xml_state *state,
 
 gpg_error_t
 result_add_string (struct result_xml_state *state,
-		   char *name, char *str)
+		   const char *name, const char *str)
 {
   if (!str)
     str = "";
diff --git a/src/posix-io.c b/src/posix-io.c
index 258e8ea5..c0b2f4fa 100644
--- a/src/posix-io.c
+++ b/src/posix-io.c
@@ -282,7 +282,7 @@ _gpgme_io_set_nonblocking (int fd)
 static long int
 get_max_fds (void)
 {
-  char *source = NULL;
+  const char *source = NULL;
   long int fds = -1;
   int rc;
 
diff --git a/src/version.c b/src/version.c
index a9bf7b80..8bc898ff 100644
--- a/src/version.c
+++ b/src/version.c
@@ -196,7 +196,7 @@ _gpgme_compare_versions (const char *my_version,
 const char *
 gpgme_check_version (const char *req_version)
 {
-  char *result;
+  const char *result;
   do_subsystem_inits ();
 
   /* Catch-22: We need to get at least the debug subsystem ready