diff --git a/Makefile b/Makefile
index 7eafd63..66d97e7 100644
--- a/Makefile
+++ b/Makefile
@@ -9,8 +9,16 @@ HDRS+= source/scpi_regs.h
 HDRS+= source/scpi_builtins.h
 HDRS+= source/scpi_errors.h
 
+CFLAGS      += -std=gnu99
+CFLAGS      += -Wall -Wextra -Wshadow
+CFLAGS      += -Wwrite-strings -Wold-style-definition -Winline
+CFLAGS      += -Wredundant-decls -Wfloat-equal -Wsign-compare -Wunused-function
+
+# gcc bug?
+CFLAGS      += -Wno-missing-braces
+
 all: $(SRC) $(HDRS)
-	gcc $(SRC) -o main.elf
+	gcc $(CFLAGS) $(SRC) -o main.elf
 
 run: all
 	./main.elf
diff --git a/main.c b/main.c
index 58e2890..7e945df 100644
--- a/main.c
+++ b/main.c
@@ -12,7 +12,7 @@ static void send_cmd(const char *cmd)
 	scpi_handle_string(cmd);
 }
 
-int main()
+int main(void)
 {
 	send_cmd("*IDN?\n"); // builtin commands..
 	send_cmd("*SRE 4\n"); // enable SRQ on error
@@ -93,6 +93,8 @@ void cmd_DATA_BLOB_data(const uint8_t *bytes)
 
 void cmd_USRERR_cb(const SCPI_argval_t *args)
 {
+	(void) args;
+
 	printf("cb USRERR - raising user error 10.\n");
 	scpi_add_error(10, "Custom error message...");
 }
diff --git a/scpi b/scpi
new file mode 100755
index 0000000..939e605
Binary files /dev/null and b/scpi differ
diff --git a/scpi.pro.user b/scpi.pro.user
index f2d5683..bf950fc 100644
--- a/scpi.pro.user
+++ b/scpi.pro.user
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE QtCreatorProject>
-<!-- Written by QtCreator 3.5.1, 2015-12-05T19:13:04. -->
+<!-- Written by QtCreator 3.5.1, 2015-12-05T21:07:16. -->
 <qtcreator>
  <data>
   <variable>EnvironmentId</variable>
@@ -70,21 +70,9 @@
    <value type="int" key="ProjectExplorer.Target.ActiveDeployConfiguration">0</value>
    <value type="int" key="ProjectExplorer.Target.ActiveRunConfiguration">0</value>
    <valuemap type="QVariantMap" key="ProjectExplorer.Target.BuildConfiguration.0">
-    <value type="QString" key="ProjectExplorer.BuildConfiguration.BuildDirectory">/home/ondra/stm32/build-scpi-Desktop-Debug</value>
+    <value type="QString" key="ProjectExplorer.BuildConfiguration.BuildDirectory">/home/ondra/stm32/scpi_</value>
     <valuemap type="QVariantMap" key="ProjectExplorer.BuildConfiguration.BuildStepList.0">
      <valuemap type="QVariantMap" key="ProjectExplorer.BuildStepList.Step.0">
-      <value type="bool" key="ProjectExplorer.BuildStep.Enabled">true</value>
-      <value type="QString" key="ProjectExplorer.ProjectConfiguration.DefaultDisplayName">qmake</value>
-      <value type="QString" key="ProjectExplorer.ProjectConfiguration.DisplayName"></value>
-      <value type="QString" key="ProjectExplorer.ProjectConfiguration.Id">QtProjectManager.QMakeBuildStep</value>
-      <value type="bool" key="QtProjectManager.QMakeBuildStep.LinkQmlDebuggingLibrary">false</value>
-      <value type="bool" key="QtProjectManager.QMakeBuildStep.LinkQmlDebuggingLibraryAuto">true</value>
-      <value type="QString" key="QtProjectManager.QMakeBuildStep.QMakeArguments"></value>
-      <value type="bool" key="QtProjectManager.QMakeBuildStep.QMakeForced">false</value>
-      <value type="bool" key="QtProjectManager.QMakeBuildStep.SeparateDebugInfo">false</value>
-      <value type="bool" key="QtProjectManager.QMakeBuildStep.UseQtQuickCompiler">false</value>
-     </valuemap>
-     <valuemap type="QVariantMap" key="ProjectExplorer.BuildStepList.Step.1">
       <value type="bool" key="ProjectExplorer.BuildStep.Enabled">true</value>
       <value type="QString" key="ProjectExplorer.ProjectConfiguration.DefaultDisplayName">Make</value>
       <value type="QString" key="ProjectExplorer.ProjectConfiguration.DisplayName"></value>
@@ -97,7 +85,7 @@
       <value type="QString" key="Qt4ProjectManager.MakeStep.MakeArguments"></value>
       <value type="QString" key="Qt4ProjectManager.MakeStep.MakeCommand"></value>
      </valuemap>
-     <value type="int" key="ProjectExplorer.BuildStepList.StepsCount">2</value>
+     <value type="int" key="ProjectExplorer.BuildStepList.StepsCount">1</value>
      <value type="QString" key="ProjectExplorer.ProjectConfiguration.DefaultDisplayName">Build</value>
      <value type="QString" key="ProjectExplorer.ProjectConfiguration.DisplayName"></value>
      <value type="QString" key="ProjectExplorer.ProjectConfiguration.Id">ProjectExplorer.BuildSteps.Build</value>
diff --git a/source/scpi_builtins.c b/source/scpi_builtins.c
index fa97e1f..a597a28 100644
--- a/source/scpi_builtins.c
+++ b/source/scpi_builtins.c
@@ -16,6 +16,8 @@ static char sbuf[256];
 
 static void builtin_CLS(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	// clear the registers
 	SCPI_REG_SESR.u8 = 0;
 	SCPI_REG_OPER.u16 = 0;
@@ -32,6 +34,8 @@ static void builtin_CLS(const SCPI_argval_t *args)
 
 static void builtin_RST(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	if (scpi_user_RST) {
 		scpi_user_RST();
 	}
@@ -40,6 +44,8 @@ static void builtin_RST(const SCPI_argval_t *args)
 
 static void builtin_TSTq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	if (scpi_user_TSTq) {
 		scpi_user_TSTq();
 	}
@@ -48,6 +54,8 @@ static void builtin_TSTq(const SCPI_argval_t *args)
 
 static void builtin_IDNq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	scpi_send_string(scpi_device_identifier());
 }
 
@@ -61,6 +69,8 @@ static void builtin_ESE(const SCPI_argval_t *args)
 
 static void builtin_ESEq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	sprintf(sbuf, "%d", SCPI_REG_SESR_EN.u8);
 	scpi_send_string(sbuf);
 }
@@ -68,6 +78,8 @@ static void builtin_ESEq(const SCPI_argval_t *args)
 
 static void builtin_ESRq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	sprintf(sbuf, "%d", SCPI_REG_SESR.u8);
 	scpi_send_string(sbuf);
 
@@ -78,6 +90,8 @@ static void builtin_ESRq(const SCPI_argval_t *args)
 
 static void builtin_OPC(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	// implementation for instruments with no overlapping commands.
 	// Can be overridden in the user commands.
 	SCPI_REG_SESR.OPC = 1;
@@ -87,6 +101,8 @@ static void builtin_OPC(const SCPI_argval_t *args)
 
 static void builtin_OPCq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	// implementation for instruments with no overlapping commands.
 	// Can be overridden in the user commands.
 	// (would be): sprintf(sbuf, "%d", SCPI_REG_SESR.OPC);
@@ -104,6 +120,8 @@ static void builtin_SRE(const SCPI_argval_t *args)
 
 static void builtin_SREq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	sprintf(sbuf, "%d", SCPI_REG_SRE.u8);
 	scpi_send_string(sbuf);
 }
@@ -111,6 +129,8 @@ static void builtin_SREq(const SCPI_argval_t *args)
 
 static void builtin_STBq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	sprintf(sbuf, "%d", SCPI_REG_STB.u8);
 	scpi_send_string(sbuf);
 }
@@ -118,12 +138,16 @@ static void builtin_STBq(const SCPI_argval_t *args)
 
 static void builtin_WAI(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	// no-op
 }
 
 
 static void builtin_SYST_ERR_NEXTq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	scpi_read_error(sbuf);
 	scpi_send_string(sbuf);
 }
@@ -132,6 +156,8 @@ static void builtin_SYST_ERR_NEXTq(const SCPI_argval_t *args)
 // optional
 static void builtin_SYST_ERR_ALLq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	int cnt = 0;
 	while (scpi_error_count()) {
 		scpi_read_error(sbuf);
@@ -145,6 +171,8 @@ static void builtin_SYST_ERR_ALLq(const SCPI_argval_t *args)
 
 static void builtin_SYST_ERR_CODE_NEXTq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	scpi_read_error(sbuf);
 
 	// end at comma
@@ -162,6 +190,8 @@ static void builtin_SYST_ERR_CODE_NEXTq(const SCPI_argval_t *args)
 // optional
 static void builtin_SYST_ERR_CODE_ALLq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	int cnt = 0;
 	while (scpi_error_count()) {
 		scpi_read_error(sbuf);
@@ -185,6 +215,8 @@ static void builtin_SYST_ERR_CODE_ALLq(const SCPI_argval_t *args)
 // optional
 static void builtin_SYST_ERR_COUNq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	sprintf(sbuf, "%d", scpi_error_count());
 	scpi_send_string(sbuf);
 }
@@ -193,18 +225,24 @@ static void builtin_SYST_ERR_COUNq(const SCPI_argval_t *args)
 // optional, custom
 static void builtin_SYST_ERR_CLEAR(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	scpi_clear_errors();
 }
 
 
 static void builtin_SYST_VERSq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	scpi_send_string("1999.0"); // implemented SCPI version
 }
 
 
 static void builtin_STAT_OPER_EVENq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	// read and clear
 	sprintf(sbuf, "%d", SCPI_REG_OPER.u16);
 	SCPI_REG_OPER.u16 = 0x0000;
@@ -215,6 +253,8 @@ static void builtin_STAT_OPER_EVENq(const SCPI_argval_t *args)
 
 static void builtin_STAT_OPER_CONDq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	// read and keep
 	sprintf(sbuf, "%d", SCPI_REG_OPER.u16);
 	scpi_send_string(sbuf);
@@ -230,6 +270,8 @@ static void builtin_STAT_OPER_ENAB(const SCPI_argval_t *args)
 
 static void builtin_STAT_OPER_ENABq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	sprintf(sbuf, "%d", SCPI_REG_OPER_EN.u16);
 	scpi_send_string(sbuf);
 }
@@ -237,6 +279,8 @@ static void builtin_STAT_OPER_ENABq(const SCPI_argval_t *args)
 
 static void builtin_STAT_QUES_EVENq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	// read and clear
 	sprintf(sbuf, "%d", SCPI_REG_QUES.u16);
 	SCPI_REG_QUES.u16 = 0x0000;
@@ -247,6 +291,8 @@ static void builtin_STAT_QUES_EVENq(const SCPI_argval_t *args)
 
 static void builtin_STAT_QUES_CONDq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	// read and keep
 	sprintf(sbuf, "%d", SCPI_REG_QUES.u16);
 	scpi_send_string(sbuf);
@@ -262,6 +308,8 @@ static void builtin_STAT_QUES_ENAB(const SCPI_argval_t *args)
 
 static void builtin_STAT_QUES_ENABq(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	sprintf(sbuf, "%d", SCPI_REG_QUES_EN.u16);
 	scpi_send_string(sbuf);
 }
@@ -269,6 +317,8 @@ static void builtin_STAT_QUES_ENABq(const SCPI_argval_t *args)
 
 static void builtin_STAT_PRES(const SCPI_argval_t *args)
 {
+	(void)args;
+
 	// Command required by SCPI spec, useless for this SCPI implementation.
 	// This is meant to preset transition and filter registers, which are not used here.
 
diff --git a/source/scpi_errors.c b/source/scpi_errors.c
index 7ce33bb..6cd968d 100644
--- a/source/scpi_errors.c
+++ b/source/scpi_errors.c
@@ -23,11 +23,9 @@ static struct {
 
 void scpi_add_error(int16_t errno, const char *extra)
 {
-	bool added = true;
 	if (erq.count >= ERR_QUEUE_LEN) {
 		errno = E_DEV_QUEUE_OVERFLOW;
 		extra = NULL;
-		added = false; // replaced only
 
 		// backtrack
 		erq.w_pos--;
diff --git a/source/scpi_parser.c b/source/scpi_parser.c
index 0849095..f27af77 100644
--- a/source/scpi_parser.c
+++ b/source/scpi_parser.c
@@ -16,7 +16,7 @@
 
 // Char matching
 #define INRANGE(c, a, b) ((c) >= (a) && (c) <= (b))
-#define IS_WHITESPACE(c) (INRANGE((c), 0, 9) || INRANGE((c), 11, 32))
+#define IS_WHITESPACE(c) ((c) <= 9 || INRANGE((c), 11, 32))
 
 #define IS_LCASE_CHAR(c) INRANGE((c), 'a', 'z')
 #define IS_UCASE_CHAR(c) INRANGE((c), 'A', 'Z')
@@ -135,7 +135,7 @@ void scpi_send_string(const char *message)
 
 // ------- Error shortcuts ----------
 
-static void err_no_such_command()
+static void err_no_such_command(void)
 {
 	char *b = ebuf;
 	for (int i = 0; i < pst.cur_level_i; i++) {
@@ -147,7 +147,7 @@ static void err_no_such_command()
 }
 
 
-static void err_no_such_command_partial()
+static void err_no_such_command_partial(void)
 {
 	char *b = ebuf;
 	for (int i = 0; i < pst.cur_level_i; i++) {