diff --git a/Makefile.am b/Makefile.am
index c57b2db..6ee27a8 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -12,7 +12,7 @@ endif
 
 ACLOCAL_AMFLAGS =-I m4
 AUTOMAKE_OPTIONS = foreign subdir-objects
-AM_CPPFLAGS=-I. -I$(srcdir)/include "-D_U_=__attribute__((unused))"
+AM_CPPFLAGS=-I. -I$(srcdir)/include
 AM_CFLAGS=$(WARN_CFLAGS)
 
 EXTRA_DIST = autogen.sh COPYING LICENCE-GPL-2.txt LICENCE-LGPL-2.1.txt \
diff --git a/aros/Makefile.AROS b/aros/Makefile.AROS
index d3042da..211d049 100755
--- a/aros/Makefile.AROS
+++ b/aros/Makefile.AROS
@@ -1,6 +1,6 @@
 AR=ar
 CC=gcc
-CFLAGS=-g -O0 -DAROS=1 -D_U_=" " -DHAVE_SYS_TYPES_H -DHAVE_SOCKADDR_LEN -I. -Iinclude -Iaros
+CFLAGS=-g -O0 -DAROS=1 -DHAVE_SYS_TYPES_H -DHAVE_SOCKADDR_LEN -I. -Iinclude -Iaros
 
 OBJS=lib/connect.o lib/crc32c.o lib/discovery.o lib/init.o lib/iscsi-command.o lib/logging.o lib/login.o lib/md5.o lib/nop.o lib/pdu.o lib/scsi-lowlevel.o lib/socket.o lib/sync.o lib/task_mgmt.o aros/aros_compat.o
 
diff --git a/aros/iscsi-ls.c b/aros/iscsi-ls.c
index 43cf048..23df2ed 100644
--- a/aros/iscsi-ls.c
+++ b/aros/iscsi-ls.c
@@ -219,7 +219,7 @@ void list_luns(struct client_state *clnt, const char *target, const char *portal
 
 
 
-void discoverylogout_cb(struct iscsi_context *iscsi, int status, void *command_data _U_, void *private_data)
+void discoverylogout_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	struct client_state *state = (struct client_state *)private_data;
 
@@ -259,7 +259,7 @@ void discovery_cb(struct iscsi_context *iscsi, int status, void *command_data, v
 }
 
 
-void discoverylogin_cb(struct iscsi_context *iscsi, int status, void *command_data _U_, void *private_data)
+void discoverylogin_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	if (status != 0) {
 		fprintf(stderr, "Login failed. %s\n", iscsi_get_error(iscsi));
@@ -272,7 +272,7 @@ void discoverylogin_cb(struct iscsi_context *iscsi, int status, void *command_da
 	}
 }
 
-void discoveryconnect_cb(struct iscsi_context *iscsi, int status, void *command_data _U_, void *private_data)
+void discoveryconnect_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	if (status != 0) {
 		fprintf(stderr, "discoveryconnect_cb: connection failed : %s\n", iscsi_get_error(iscsi));
diff --git a/configure.ac b/configure.ac
index db8d6bf..756b189 100644
--- a/configure.ac
+++ b/configure.ac
@@ -30,6 +30,7 @@ AC_ARG_ENABLE([werror], [AS_HELP_STRING([--disable-werror],
 if test "$ac_cv_prog_gcc" = yes; then
    WARN_CFLAGS="-Wall -W -Wshadow -Wstrict-prototypes -Wpointer-arith -Wcast-align -Wcast-qual -Wno-strict-aliasing -Wvla"
    WARN_CFLAGS="$WARN_CFLAGS -Wno-unknown-warning-option -Wno-stringop-truncation"
+   WARN_CFLAGS="$WARN_CFLAGS -Wno-unused-parameter"
    if test "x$enable_werror" != "xno"; then
        WARN_CFLAGS="$WARN_CFLAGS -Werror"
    fi
diff --git a/examples/Makefile.am b/examples/Makefile.am
index 28e5af1..fa439ff 100644
--- a/examples/Makefile.am
+++ b/examples/Makefile.am
@@ -1,4 +1,4 @@
-AM_CPPFLAGS=-I. -I${srcdir}/../include "-D_U_=__attribute__((unused))"
+AM_CPPFLAGS=-I. -I${srcdir}/../include
 AM_CFLAGS=$(WARN_CFLAGS)
 AM_LDFLAGS=-no-undefined
 LIBS=../lib/libiscsi.la
diff --git a/examples/iscsi-dd.c b/examples/iscsi-dd.c
index 2daae44..4c97499 100644
--- a/examples/iscsi-dd.c
+++ b/examples/iscsi-dd.c
@@ -102,7 +102,7 @@ void write_cb(struct iscsi_context *iscsi, int status, void *command_data, void
 	free(wt);
 }
 
-void read_cb(struct iscsi_context *iscsi _U_, int status, void *command_data, void *private_data)
+void read_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	struct client *client = (struct client *)private_data;
 	struct scsi_task *task = command_data;
@@ -276,7 +276,7 @@ void populate_param_header(unsigned char *buf, int list_id, int str, int list_id
 	buf[15] = inline_data_len & 0xFF;
 }
 
-void xcopy_cb(struct iscsi_context *iscsi _U_, int status, void *command_data, void *private_data)
+void xcopy_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	struct client *client = (struct client *)private_data;
 	struct scsi_task *task = command_data;
diff --git a/examples/iscsiclient.c b/examples/iscsiclient.c
index a61d6e0..7bbe06d 100644
--- a/examples/iscsiclient.c
+++ b/examples/iscsiclient.c
@@ -63,7 +63,7 @@ struct client_state {
 
 unsigned char small_buffer[512];
 
-void tm_at_cb(struct iscsi_context *iscsi _U_, int status _U_, void *command_data _U_, void *private_data)
+void tm_at_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	struct client_state *clnt = (struct client_state *)private_data;
 
@@ -74,7 +74,7 @@ void tm_at_cb(struct iscsi_context *iscsi _U_, int status _U_, void *command_dat
 }
 
 
-void synccache10_cb(struct iscsi_context *iscsi _U_, int status, void *command_data _U_, void *private_data _U_)
+void synccache10_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	printf("SYNCCACHE10 status:%d\n", status);
 }
@@ -103,7 +103,7 @@ void nop_out_cb(struct iscsi_context *iscsi, int status, void *command_data, voi
 }
 
 
-void write10_1_cb(struct iscsi_context *iscsi _U_, int status, void *command_data, void *private_data _U_)
+void write10_1_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	struct scsi_task *task = command_data;
 
@@ -123,7 +123,7 @@ void write10_1_cb(struct iscsi_context *iscsi _U_, int status, void *command_dat
 	exit(10);
 }
 
-void write10_cb(struct iscsi_context *iscsi _U_, int status, void *command_data, void *private_data _U_)
+void write10_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	struct client_state *clnt = (struct client_state *)private_data;
 	struct scsi_task *task = command_data;
@@ -482,7 +482,7 @@ void reportluns_cb(struct iscsi_context *iscsi, int status, void *command_data,
 }
 
 
-void normallogin_cb(struct iscsi_context *iscsi, int status, void *command_data _U_, void *private_data)
+void normallogin_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	if (status != 0) {
 		printf("Failed to log in to target : %s\n", iscsi_get_error(iscsi));
@@ -497,7 +497,7 @@ void normallogin_cb(struct iscsi_context *iscsi, int status, void *command_data
 }
 
 
-void normalconnect_cb(struct iscsi_context *iscsi, int status, void *command_data _U_, void *private_data)
+void normalconnect_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	printf("Connected to iscsi socket\n");
 
@@ -517,7 +517,7 @@ void normalconnect_cb(struct iscsi_context *iscsi, int status, void *command_dat
 
 
 
-void discoverylogout_cb(struct iscsi_context *iscsi, int status, void *command_data _U_, void *private_data)
+void discoverylogout_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	struct client_state *clnt = (struct client_state *)private_data;
 	
@@ -586,7 +586,7 @@ void discovery_cb(struct iscsi_context *iscsi, int status, void *command_data, v
 }
 
 
-void discoverylogin_cb(struct iscsi_context *iscsi, int status, void *command_data _U_, void *private_data)
+void discoverylogin_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	if (status != 0) {
 		printf("Failed to log in to target. : %s\n", iscsi_get_error(iscsi));
@@ -601,7 +601,7 @@ void discoverylogin_cb(struct iscsi_context *iscsi, int status, void *command_da
 
 }
 
-void discoveryconnect_cb(struct iscsi_context *iscsi, int status, void *command_data _U_, void *private_data)
+void discoveryconnect_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	printf("Connected to iscsi socket status:0x%08x\n", status);
 
@@ -619,7 +619,7 @@ void discoveryconnect_cb(struct iscsi_context *iscsi, int status, void *command_
 }
 
 
-int main(int argc _U_, char *argv[] _U_)
+int main(int argc, char *argv[])
 {
 	struct iscsi_context *iscsi;
 	struct pollfd pfd;
diff --git a/include/iscsi-private.h b/include/iscsi-private.h
index e03dd0c..a649254 100644
--- a/include/iscsi-private.h
+++ b/include/iscsi-private.h
@@ -371,7 +371,7 @@ uint32_t iscsi_itt_post_increment(struct iscsi_context *iscsi);
 
 void iscsi_timeout_scan(struct iscsi_context *iscsi);
 
-void iscsi_reconnect_cb(struct iscsi_context *iscsi _U_, int status,
+void iscsi_reconnect_cb(struct iscsi_context *iscsi, int status,
                         void *command_data, void *private_data);
 
 struct iscsi_pdu *iscsi_tcp_new_pdu(struct iscsi_context *iscsi, size_t size);
diff --git a/lib/Makefile.am b/lib/Makefile.am
index 90b508e..de05776 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -22,8 +22,7 @@ endif
 
 libiscsipriv_la_LDFLAGS = -no-undefined
 
-libiscsipriv_la_CPPFLAGS = -I${srcdir}/../include -I$(srcdir)/include \
-	"-D_U_=__attribute__((unused))"
+libiscsipriv_la_CPPFLAGS = -I${srcdir}/../include -I$(srcdir)/include
 
 AM_CFLAGS=$(WARN_CFLAGS)
 
diff --git a/lib/connect.c b/lib/connect.c
index daa7007..68b6ca2 100644
--- a/lib/connect.c
+++ b/lib/connect.c
@@ -46,7 +46,7 @@ struct connect_task {
 };
 
 static void
-iscsi_connect_cb(struct iscsi_context *iscsi, int status, void *command_data _U_,
+iscsi_connect_cb(struct iscsi_context *iscsi, int status, void *command_data,
 		 void *private_data);
 
 
@@ -144,7 +144,7 @@ iscsi_testunitready_cb(struct iscsi_context *iscsi, int status,
 }
 
 static void
-iscsi_login_cb(struct iscsi_context *iscsi, int status, void *command_data _U_,
+iscsi_login_cb(struct iscsi_context *iscsi, int status, void *command_data,
 	       void *private_data)
 {
 	struct connect_task *ct = private_data;
@@ -184,7 +184,7 @@ iscsi_login_cb(struct iscsi_context *iscsi, int status, void *command_data _U_,
 }
 
 static void
-iscsi_connect_cb(struct iscsi_context *iscsi, int status, void *command_data _U_,
+iscsi_connect_cb(struct iscsi_context *iscsi, int status, void *command_data,
 		 void *private_data)
 {
 	struct connect_task *ct = private_data;
@@ -276,8 +276,8 @@ void iscsi_defer_reconnect(struct iscsi_context *iscsi)
 	iscsi_cancel_pdus(iscsi);
 }
 
-void iscsi_reconnect_cb(struct iscsi_context *iscsi _U_, int status,
-                        void *command_data _U_, void *private_data _U_)
+void iscsi_reconnect_cb(struct iscsi_context *iscsi, int status,
+                        void *command_data, void *private_data)
 {
 	struct iscsi_context *old_iscsi;
 	int i;
diff --git a/lib/iscsi-command.c b/lib/iscsi-command.c
index 3eb8e8f..a4df637 100644
--- a/lib/iscsi-command.c
+++ b/lib/iscsi-command.c
@@ -40,7 +40,7 @@
 
 static void
 iscsi_scsi_response_cb(struct iscsi_context *iscsi, int status,
-		       void *command_data _U_, void *private_data)
+		       void *command_data, void *private_data)
 {
 	struct iscsi_scsi_cbdata *scsi_cbdata =
 	  (struct iscsi_scsi_cbdata *)private_data;
@@ -2433,7 +2433,7 @@ iscsi_get_scsi_task_iovector_in(struct iscsi_context *iscsi, struct iscsi_in_pdu
 }
 
 struct scsi_iovector *
-iscsi_get_scsi_task_iovector_out(struct iscsi_context *iscsi _U_, struct iscsi_pdu *pdu)
+iscsi_get_scsi_task_iovector_out(struct iscsi_context *iscsi, struct iscsi_pdu *pdu)
 {
 	if (pdu->scsi_cbdata.task->iovector_out.iov == NULL) {
 		return NULL;
diff --git a/lib/iser.c b/lib/iser.c
index ed3b84f..bbd9662 100644
--- a/lib/iser.c
+++ b/lib/iser.c
@@ -83,7 +83,7 @@ iscsi_iser_get_fd(struct iscsi_context *iscsi)
  * Being used in QEMU iscsi block so we need compatability with TCP
  */
 static int
-iscsi_iser_which_events(struct iscsi_context *iscsi _U_)
+iscsi_iser_which_events(struct iscsi_context *iscsi)
 {
 	/* iSER is waiting to events from CQ that are always POLLIN */
 	return 1;
@@ -1401,8 +1401,8 @@ no_waitpdu:
  *
  */
 static int
-iser_snd_completion(struct iser_tx_desc *tx_desc _U_,
-		    struct iser_conn *iser_conn _U_)
+iser_snd_completion(struct iser_tx_desc *tx_desc,
+		    struct iser_conn *iser_conn)
 {
 	return 0;
 }
diff --git a/lib/login.c b/lib/login.c
index 73e7673..786ae03 100644
--- a/lib/login.c
+++ b/lib/login.c
@@ -1435,7 +1435,7 @@ iscsi_logout_async(struct iscsi_context *iscsi, iscsi_command_cb cb,
 
 int
 iscsi_process_logout_reply(struct iscsi_context *iscsi, struct iscsi_pdu *pdu,
-struct iscsi_in_pdu *in _U_)
+struct iscsi_in_pdu *in)
 {
 	iscsi->is_loggedin = 0;
 	ISCSI_LOG(iscsi, 2, "logout successful");
diff --git a/lib/pdu.c b/lib/pdu.c
index 524144a..6fe70db 100644
--- a/lib/pdu.c
+++ b/lib/pdu.c
@@ -330,7 +330,7 @@ int iscsi_process_target_nop_in(struct iscsi_context *iscsi,
 }
 
 static void iscsi_reconnect_after_logout(struct iscsi_context *iscsi, int status,
-                        void *command_data _U_, void *opaque _U_)
+                        void *command_data, void *opaque)
 {
 	if (status) {
 		ISCSI_LOG(iscsi, 1, "logout failed: %s", iscsi_get_error(iscsi));
diff --git a/lib/scsi-lowlevel.c b/lib/scsi-lowlevel.c
index 559a2b1..50ec515 100644
--- a/lib/scsi-lowlevel.c
+++ b/lib/scsi-lowlevel.c
@@ -1246,7 +1246,7 @@ scsi_cdb_report_supported_opcodes(int rctd, int options, enum scsi_opcode opcode
  * readcapacity10 datain structure
  */
 static int
-scsi_readcapacity10_datain_getfullsize(struct scsi_task *task _U_)
+scsi_readcapacity10_datain_getfullsize(struct scsi_task *task)
 {
 	return 8;
 }
diff --git a/lib/socket.c b/lib/socket.c
index dc197ff..5d3952b 100644
--- a/lib/socket.c
+++ b/lib/socket.c
@@ -1069,7 +1069,7 @@ void iscsi_set_tcp_keepintvl(struct iscsi_context *iscsi, int value)
 	ISCSI_LOG(iscsi, 2, "TCP_KEEPINTVL will be set to %d on next socket creation",value);
 }
 
-int iscsi_set_tcp_keepalive(struct iscsi_context *iscsi, int idle _U_, int count _U_, int interval _U_)
+int iscsi_set_tcp_keepalive(struct iscsi_context *iscsi, int idle, int count, int interval)
 {
 #ifdef SO_KEEPALIVE
 	int value = 1;
@@ -1104,7 +1104,7 @@ int iscsi_set_tcp_keepalive(struct iscsi_context *iscsi, int idle _U_, int count
 	return 0;
 }
 
-void iscsi_set_bind_interfaces(struct iscsi_context *iscsi, char * interfaces _U_)
+void iscsi_set_bind_interfaces(struct iscsi_context *iscsi, char * interfaces)
 {
 #if __linux
 	strncpy(iscsi->bind_interfaces,interfaces,MAX_STRING_SIZE);
diff --git a/lib/sync.c b/lib/sync.c
index e46a206..36ef6f0 100644
--- a/lib/sync.c
+++ b/lib/sync.c
@@ -82,8 +82,8 @@ event_loop(struct iscsi_context *iscsi, struct iscsi_sync_state *state)
  * Synchronous iSCSI commands
  */
 static void
-iscsi_sync_cb(struct iscsi_context *iscsi _U_, int status,
-	      void *command_data _U_, void *private_data)
+iscsi_sync_cb(struct iscsi_context *iscsi, int status,
+	      void *command_data, void *private_data)
 {
 	struct iscsi_sync_state *state = private_data;
 
@@ -340,7 +340,7 @@ iscsi_task_mgmt_target_cold_reset_sync(struct iscsi_context *iscsi)
  * Synchronous SCSI commands
  */
 static void
-scsi_sync_cb(struct iscsi_context *iscsi _U_, int status, void *command_data,
+scsi_sync_cb(struct iscsi_context *iscsi, int status, void *command_data,
 	     void *private_data)
 {
 	struct scsi_task *task = command_data;
@@ -1820,7 +1820,7 @@ iscsi_modesense10_sync(struct iscsi_context *iscsi, int lun, int llbaa, int dbd,
 	return state.task;
 }
 
-void iscsi_free_discovery_data(struct iscsi_context *iscsi _U_,
+void iscsi_free_discovery_data(struct iscsi_context *iscsi,
                                struct iscsi_discovery_address *da)
 {
         while (da) {
@@ -1840,7 +1840,7 @@ void iscsi_free_discovery_data(struct iscsi_context *iscsi _U_,
 }
 
 static void
-iscsi_discovery_cb(struct iscsi_context *iscsi _U_, int status,
+iscsi_discovery_cb(struct iscsi_context *iscsi, int status,
 	      void *command_data, void *private_data)
 {
 	struct iscsi_sync_state *state = private_data;
diff --git a/test-tool/Makefile.am b/test-tool/Makefile.am
index 6f75666..a39bf3e 100644
--- a/test-tool/Makefile.am
+++ b/test-tool/Makefile.am
@@ -1,5 +1,4 @@
-AM_CPPFLAGS=-I. -I${srcdir}/../include \
-	"-D_U_=__attribute__((unused)) "
+AM_CPPFLAGS=-I. -I${srcdir}/../include
 AM_CFLAGS=$(WARN_CFLAGS)
 AM_LDFLAGS=-no-undefined
 LIBS = ../lib/libiscsipriv.la
diff --git a/test-tool/test_iscsi_nop_simple.c b/test-tool/test_iscsi_nop_simple.c
index b45ab30..7f5c4fe 100644
--- a/test-tool/test_iscsi_nop_simple.c
+++ b/test-tool/test_iscsi_nop_simple.c
@@ -57,7 +57,7 @@ test_iscsi_nop_txrx(struct test_iscsi_nop_state *state)
 }
 
 static void
-test_iscsi_nop_cb(struct iscsi_context *iscsi _U_, int status,
+test_iscsi_nop_cb(struct iscsi_context *iscsi, int status,
                   void *command_data, void *private_data)
 {
         struct test_iscsi_nop_state *state = private_data;
diff --git a/test-tool/test_iscsi_sendtargets.c b/test-tool/test_iscsi_sendtargets.c
index e4ac6d2..e7a1892 100644
--- a/test-tool/test_iscsi_sendtargets.c
+++ b/test-tool/test_iscsi_sendtargets.c
@@ -59,8 +59,8 @@ test_iscsi_sendtargets_txrx(struct test_iscsi_sendtargets_state *state)
 }
 
 static void
-test_iscsi_sendtargets_cb(struct iscsi_context *iscsi _U_, int status,
-                          void *command_data _U_, void *private_data)
+test_iscsi_sendtargets_cb(struct iscsi_context *iscsi, int status,
+                          void *command_data, void *private_data)
 {
         struct test_iscsi_sendtargets_state *state = private_data;
 
diff --git a/test-tool/test_sanitize_reset.c b/test-tool/test_sanitize_reset.c
index 19d1fb5..fffc55a 100644
--- a/test-tool/test_sanitize_reset.c
+++ b/test-tool/test_sanitize_reset.c
@@ -26,8 +26,8 @@
 #include "scsi-lowlevel.h"
 #include "iscsi-test-cu.h"
 
-static void sanitize_cb(struct iscsi_context *iscsi _U_, int status _U_,
-       void *command_data _U_, void *private_data _U_)
+static void sanitize_cb(struct iscsi_context *iscsi, int status,
+       void *command_data, void *private_data)
 {
 }
 
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 6423e85..599033b 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1,4 +1,4 @@
-AM_CPPFLAGS = -I${srcdir}/../include "-D_U_=__attribute__((unused))"
+AM_CPPFLAGS = -I${srcdir}/../include
 AM_CFLAGS = $(WARN_CFLAGS)
 AM_LDFLAGS = -no-undefined
 LIBS = ../lib/libiscsi.la
diff --git a/tests/prog_header_digest.c b/tests/prog_header_digest.c
index 9668654..357ba9f 100644
--- a/tests/prog_header_digest.c
+++ b/tests/prog_header_digest.c
@@ -82,8 +82,8 @@ void event_loop(struct iscsi_context *iscsi, struct client_state *state,
 	}
 }
 
-void tur_cb(struct iscsi_context *iscsi _U_, int status,
-	    void *command_data _U_, void *private_data)
+void tur_cb(struct iscsi_context *iscsi, int status,
+	    void *command_data, void *private_data)
 {
 	struct client_state *state = (struct client_state *)private_data;
 
diff --git a/tests/prog_noop_reply.c b/tests/prog_noop_reply.c
index f6a2d2c..a844ce2 100644
--- a/tests/prog_noop_reply.c
+++ b/tests/prog_noop_reply.c
@@ -82,8 +82,8 @@ void event_loop(struct iscsi_context *iscsi, struct client_state *state,
 	}
 }
 
-void tur_cb(struct iscsi_context *iscsi _U_, int status,
-	    void *command_data _U_, void *private_data)
+void tur_cb(struct iscsi_context *iscsi, int status,
+	    void *command_data, void *private_data)
 {
 	struct client_state *state = (struct client_state *)private_data;
 
diff --git a/tests/prog_read_all_pdus.c b/tests/prog_read_all_pdus.c
index 0f4d19a..2c30d7c 100644
--- a/tests/prog_read_all_pdus.c
+++ b/tests/prog_read_all_pdus.c
@@ -68,8 +68,8 @@ void print_help(void)
 	fprintf(stderr, "  \"ipv6-address\"   [fce0::1]\n");
 }
 
-void tur_cb(struct iscsi_context *iscsi _U_, int status _U_,
-	       void *command_data _U_, void *private_data)
+void tur_cb(struct iscsi_context *iscsi, int status,
+	       void *command_data, void *private_data)
 {
         int *count = (int *)private_data;
         
diff --git a/tests/prog_reconnect.c b/tests/prog_reconnect.c
index 9012cca..ba7871f 100644
--- a/tests/prog_reconnect.c
+++ b/tests/prog_reconnect.c
@@ -73,7 +73,7 @@ void event_loop(struct iscsi_context *iscsi, struct client_state *state)
 }
 
 void logout_cb(struct iscsi_context *iscsi, int status,
-	       void *command_data _U_, void *private_data)
+	       void *command_data, void *private_data)
 {
 	struct client_state *state = (struct client_state *)private_data;
 
diff --git a/tests/prog_reconnect_timeout.c b/tests/prog_reconnect_timeout.c
index 3693af9..d6b5881 100644
--- a/tests/prog_reconnect_timeout.c
+++ b/tests/prog_reconnect_timeout.c
@@ -83,7 +83,7 @@ void event_loop(struct iscsi_context *iscsi, struct client_state *state)
 }
 
 void logout_cb(struct iscsi_context *iscsi, int status,
-	       void *command_data _U_, void *private_data)
+	       void *command_data, void *private_data)
 {
 	struct client_state *state = (struct client_state *)private_data;
 
diff --git a/tests/prog_timeout.c b/tests/prog_timeout.c
index f6b8824..a5fc7d4 100644
--- a/tests/prog_timeout.c
+++ b/tests/prog_timeout.c
@@ -72,7 +72,7 @@ void print_help(void)
 	fprintf(stderr, "  \"ipv6-address\"   [fce0::1]\n");
 }
 
-void tur_cb(struct iscsi_context *iscsi _U_, int status, void *command_data _U_, void *private_data)
+void tur_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	uint32_t *i = private_data;
 
@@ -86,7 +86,7 @@ void tur_cb(struct iscsi_context *iscsi _U_, int status, void *command_data _U_,
 	}
 }
 
-void logout_cb(struct iscsi_context *iscsi _U_, int status, void *command_data _U_, void *private_data)
+void logout_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	uint32_t *i = private_data;
 
diff --git a/utils/Makefile.am b/utils/Makefile.am
index a8c053a..1c2684a 100644
--- a/utils/Makefile.am
+++ b/utils/Makefile.am
@@ -1,4 +1,4 @@
-AM_CPPFLAGS = -I${srcdir}/../include "-D_U_=__attribute__((unused))"
+AM_CPPFLAGS = -I${srcdir}/../include
 AM_CFLAGS = $(WARN_CFLAGS)
 AM_LDFLAGS = -no-undefined
 LIBS = ../lib/libiscsi.la
diff --git a/utils/iscsi-ls.c b/utils/iscsi-ls.c
index c446c96..dbb7ebc 100644
--- a/utils/iscsi-ls.c
+++ b/utils/iscsi-ls.c
@@ -234,7 +234,7 @@ void list_luns(struct client_state *clnt, const char *target, const char *portal
 
 
 
-void discoverylogout_cb(struct iscsi_context *iscsi, int status, void *command_data _U_, void *private_data)
+void discoverylogout_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	struct client_state *state = (struct client_state *)private_data;
 	
@@ -287,7 +287,7 @@ void discovery_cb(struct iscsi_context *iscsi, int status, void *command_data, v
 }
 
 
-void discoverylogin_cb(struct iscsi_context *iscsi, int status, void *command_data _U_, void *private_data)
+void discoverylogin_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	if (status != 0) {
 		fprintf(stderr, "Login failed. %s\n", iscsi_get_error(iscsi));
@@ -300,7 +300,7 @@ void discoverylogin_cb(struct iscsi_context *iscsi, int status, void *command_da
 	}
 }
 
-void discoveryconnect_cb(struct iscsi_context *iscsi, int status, void *command_data _U_, void *private_data)
+void discoveryconnect_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	if (status != 0) {
 		fprintf(stderr, "discoveryconnect_cb: connection failed : %s\n", iscsi_get_error(iscsi));
diff --git a/utils/iscsi-perf.c b/utils/iscsi-perf.c
index f84c180..f91496d 100644
--- a/utils/iscsi-perf.c
+++ b/utils/iscsi-perf.c
@@ -126,7 +126,7 @@ void progress(struct client *client) {
 	client->last_bytes = client->bytes;
 }
 
-void cb(struct iscsi_context *iscsi _U_, int status, void *command_data, void *private_data)
+void cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data)
 {
 	struct client *client = (struct client *)private_data;
 	struct scsi_task *task = command_data, *task2 = NULL;
diff --git a/win32/iscsi-ls/iscsi-ls.vcxproj b/win32/iscsi-ls/iscsi-ls.vcxproj
index 61d2e56..6745a6c 100644
--- a/win32/iscsi-ls/iscsi-ls.vcxproj
+++ b/win32/iscsi-ls/iscsi-ls.vcxproj
@@ -84,7 +84,7 @@
       </PrecompiledHeader>
       <WarningLevel>Level3</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;_WIN32_WINNT=0x0501;_U_=;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;_WIN32_WINNT=0x0501;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>..\..\include;..\..\.;..\..\win32</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
@@ -103,7 +103,7 @@
       </PrecompiledHeader>
       <WarningLevel>Level3</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;_WIN32_WINNT=0x0501;_U_=;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;_WIN32_WINNT=0x0501;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>..\..\include;..\..\.;..\..\win32</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
@@ -124,7 +124,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;_WIN32_WINNT=0x0501;_U_=;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;_WIN32_WINNT=0x0501;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>..\..\include;..\..\.;..\..\win32</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
@@ -143,7 +143,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;_WIN32_WINNT=0x0501;_U_=;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;_WIN32_WINNT=0x0501;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>..\..\include;..\..\.;..\..\win32</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
diff --git a/win32/libiscsi/libiscsi.vcxproj b/win32/libiscsi/libiscsi.vcxproj
index 644204f..86ddd16 100644
--- a/win32/libiscsi/libiscsi.vcxproj
+++ b/win32/libiscsi/libiscsi.vcxproj
@@ -88,7 +88,7 @@
       </PrecompiledHeader>
       <WarningLevel>Level3</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;_USRDLL;_U_=;_USE_32BIT_TIME_T;__STDC_CONSTANT_MACROS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;_USRDLL;_USE_32BIT_TIME_T;__STDC_CONSTANT_MACROS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>..\..\include;..\..\.;..\..\win32;..\..\lib</AdditionalIncludeDirectories>
       <CompileAs>Default</CompileAs>
       <DisableSpecificWarnings>4996</DisableSpecificWarnings>
@@ -111,7 +111,7 @@
       </PrecompiledHeader>
       <WarningLevel>Level3</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;_USRDLL;_U_=;__STDC_CONSTANT_MACROS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;_USRDLL;__STDC_CONSTANT_MACROS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>..\..\include;..\..\.;..\..\win32;..\..\lib</AdditionalIncludeDirectories>
       <CompileAs>Default</CompileAs>
       <DisableSpecificWarnings>4996</DisableSpecificWarnings>
@@ -136,7 +136,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;_USRDLL;_U_=;_USE_32BIT_TIME_T;__STDC_CONSTANT_MACROS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;_USRDLL;_USE_32BIT_TIME_T;__STDC_CONSTANT_MACROS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>..\..\include;..\..\.;..\..\win32;..\..\lib</AdditionalIncludeDirectories>
       <DisableSpecificWarnings>4996</DisableSpecificWarnings>
     </ClCompile>
@@ -161,7 +161,7 @@
       <Optimization>Full</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;_USRDLL;_U_=;__STDC_CONSTANT_MACROS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;_USRDLL;__STDC_CONSTANT_MACROS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>..\..\include;..\..\.;..\..\win32;..\..\lib</AdditionalIncludeDirectories>
       <DisableSpecificWarnings>4996</DisableSpecificWarnings>
       <InlineFunctionExpansion>AnySuitable</InlineFunctionExpansion>