build: Don't use 0 as NULL/nullptr in pointer compare and assignment

src/configure.ac

@@ -1728,6 +1728,19 @@ add_to_cflags() {
 # Always add -Wextra
 add_to_cflags "-Wextra"
 
+# Add option to enable warnings when integer 0 is used to act
+# as NULL or nullptr in assignment or comparison.
+AC_ARG_ENABLE(wzero-as-null-pointer-constant,
+    AS_HELP_STRING(
+      [--enable-wzero-as-null-pointer-constant],
+      [Warn on zero being used as NULL pointer constant (-Wzero-as-null-pointer-constant).],
+    ),
+    [
+      case "$enableval" in
+        (yes) add_to_cflags "-Wzero-as-null-pointer-constant" ;;
+      esac
+    ])
+
 # The last thing before subst-exporting CFLAGS and CXXFLAGS is to add -Werror
 # if requested. Doing it earlier causes conf-tests to fail that are supposed to
 # succeed when they generate warnings.

src/emc/canterp/canterp.cc

@@ -67,7 +67,7 @@ static char the_command_args[LINELEN] = { 0 };	// just the args part
 
 class Canterp : public InterpBase {
 public:
-    Canterp () : f(0), filename{} {}
+    Canterp () : f(NULL), filename{} {}
     char *error_text(int errcode, char *buf, size_t buflen) override;
     char *stack_name(int index, char *buf, size_t buflen) override;
     char *line_text(char *buf, size_t buflen) override;
@@ -209,7 +209,7 @@ static int canterp_parse(char *buffer)
        now we're at the args; skip first and last quotes when building
        args_ptr, and make commas spaces for easy parsing later
      */
-    last_quote_ptr = 0;
+    last_quote_ptr = NULL;
     inquote = 0;
     while (')' != *ptr && 0 != *ptr) {
 	if ('"' == *ptr) {
@@ -235,7 +235,7 @@ static int canterp_parse(char *buffer)
 	*cmd_ptr = 0;
 	return INTERP_ERROR;
     }
-    if (0 != last_quote_ptr)
+    if (NULL != last_quote_ptr)
 	*last_quote_ptr = 0;
     *args_ptr = 0;
     *cmd_ptr++ = ')';
@@ -692,7 +692,7 @@ int Canterp::execute(const char *line, int /*line_number*/) {
 }
 
 int Canterp::execute() {
-    return execute(0);
+    return execute(NULL);
 }
 
 int Canterp::open(const char *newfilename) {

src/emc/ini/inifile.cc

@@ -1106,9 +1106,9 @@ std::optional<rtapi_s64> IniFile::convertSInt(const std::string &_val)
 	char *eptr;
 
 	// Make sure we always use the C locale for conversion (thread local)
-	locale_t olc = uselocale(static_cast<locale_t>(0));
-	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(0));
-	if(static_cast<locale_t>(0) == nlc) {
+	locale_t olc = uselocale(static_cast<locale_t>(nullptr));
+	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(nullptr));
+	if(static_cast<locale_t>(nullptr) == nlc) {
 		print_msg("internal error: ConvertSInt(): Cannot set locale to \"C\" for strtoll");
 		return std::nullopt;
 	}
@@ -1135,9 +1135,9 @@ std::optional<rtapi_s64> IniFile::convertSInt(const IniFileTag *val) const
 	char *eptr;
 
 	// Make sure we always use the C locale for conversion (thread local)
-	locale_t olc = uselocale(static_cast<locale_t>(0));
-	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(0));
-	if(static_cast<locale_t>(0) == nlc) {
+	locale_t olc = uselocale(static_cast<locale_t>(nullptr));
+	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(nullptr));
+	if(static_cast<locale_t>(nullptr) == nlc) {
 		print_msg(fmt::format("{}:{}: internal error: Cannot set locale to \"C\" for strtoll", val->path, val->lineno));
 		return std::nullopt;
 	}
@@ -1171,9 +1171,9 @@ std::optional<rtapi_u64> IniFile::convertUInt(const std::string &_val)
 	}
 
 	// Make sure we always use the C locale for conversion (thread local)
-	locale_t olc = uselocale(static_cast<locale_t>(0));
-	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(0));
-	if(static_cast<locale_t>(0) == nlc) {
+	locale_t olc = uselocale(static_cast<locale_t>(nullptr));
+	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(nullptr));
+	if(static_cast<locale_t>(nullptr) == nlc) {
 		print_msg("internal error: ConvertUInt(): Cannot set locale to \"C\" for strtoull");
 		return std::nullopt;
 	}
@@ -1205,9 +1205,9 @@ std::optional<rtapi_u64> IniFile::convertUInt(const IniFileTag *val) const
 	}
 
 	// Make sure we always use the C locale for conversion (thread local)
-	locale_t olc = uselocale(static_cast<locale_t>(0));
-	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(0));
-	if(static_cast<locale_t>(0) == nlc) {
+	locale_t olc = uselocale(static_cast<locale_t>(nullptr));
+	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(nullptr));
+	if(static_cast<locale_t>(nullptr) == nlc) {
 		print_msg(fmt::format("{}:{}: internal error: Cannot set locale to \"C\" for strtoull", val->path, val->lineno));
 		return std::nullopt;
 	}
@@ -1235,9 +1235,9 @@ std::optional<double> IniFile::convertReal(const std::string &val)
 	char *eptr;
 
 	// Make sure we always use the C locale for conversion (thread local)
-	locale_t olc = uselocale(static_cast<locale_t>(0));
-	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(0));
-	if(static_cast<locale_t>(0) == nlc) {
+	locale_t olc = uselocale(static_cast<locale_t>(nullptr));
+	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(nullptr));
+	if(static_cast<locale_t>(nullptr) == nlc) {
 		print_msg("internal error: ConvertReal(): Cannot set locale to \"C\" for strtod");
 		return std::nullopt;
 	}
@@ -1262,9 +1262,9 @@ std::optional<double> IniFile::convertReal(const IniFileTag *val) const
 	char *eptr;
 
 	// Make sure we always use the C locale for conversion (thread local)
-	locale_t olc = uselocale(static_cast<locale_t>(0));
-	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(0));
-	if(static_cast<locale_t>(0) == nlc) {
+	locale_t olc = uselocale(static_cast<locale_t>(nullptr));
+	locale_t nlc = newlocale(LC_NUMERIC_MASK, "C", static_cast<locale_t>(nullptr));
+	if(static_cast<locale_t>(nullptr) == nlc) {
 		print_msg(fmt::format("{}:{}: internal error: Cannot set locale to \"C\" for strtod", val->path, val->lineno));
 		return std::nullopt;
 	}

src/emc/ini/inihal.cc

@@ -144,7 +144,7 @@ int ini_hal_init(int numjoints)
     }
 
     the_inihal_data = (ptr_inihal_data *) hal_malloc(sizeof(ptr_inihal_data));
-    if (the_inihal_data == 0) {
+    if (the_inihal_data == NULL) {
         rtapi_print_msg(RTAPI_MSG_ERR,
                        "ini_hal_init: ERROR: hal_malloc() failed\n");
         hal_exit(comp_id);

src/emc/kinematics/genserfuncs.c

@@ -62,7 +62,7 @@ static struct haldata {
     genser_struct *kins;
     go_pose *pos; // used in various functions, we malloc it
                   // only once in genserKinematicsSetup()
-} *haldata = 0;
+} *haldata = NULL;
 
 static int total_joints;
 double j[GENSER_MAX_JOINTS];

src/emc/kinematics/lineardeltakins.cc

@@ -46,6 +46,8 @@ static object get_geometry()
     return make_tuple(R, L);
 }
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
 BOOST_PYTHON_MODULE(lineardeltakins)
 {
     set_geometry(DELTA_RADIUS, DELTA_DIAGONAL_ROD);
@@ -54,3 +56,4 @@ BOOST_PYTHON_MODULE(lineardeltakins)
     def("forward", forward);
     def("inverse", inverse);
 }
+#pragma GCC diagnostic pop

src/emc/kinematics/rotarydeltakins.cc

@@ -45,6 +45,8 @@ static object get_geometry()
     return make_tuple(platformradius, thighlength, shinlength, footradius);
 }
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
 BOOST_PYTHON_MODULE(rotarydeltakins)
 {
     set_geometry(RDELTA_PFR, RDELTA_TL, RDELTA_SL, RDELTA_FR);
@@ -53,3 +55,4 @@ BOOST_PYTHON_MODULE(rotarydeltakins)
     def("forward", forward);
     def("inverse", inverse);
 }
+#pragma GCC diagnostic pop

src/emc/motion-logger/motion-logger.c

@@ -44,13 +44,13 @@ static struct motion_logger_data_t {
 FILE *logfile = NULL;
 char *logfile_name = NULL;
 
-emcmot_struct_t *emcmotStruct = 0;
+emcmot_struct_t *emcmotStruct = NULL;
 
-struct emcmot_command_t *c = 0;
-struct emcmot_status_t *emcmotStatus = 0;
-struct emcmot_config_t *emcmotConfig = 0;
-struct emcmot_internal_t *emcmotInternal = 0;
-struct emcmot_error_t *emcmotError = 0;
+struct emcmot_command_t *c = NULL;
+struct emcmot_status_t *emcmotStatus = NULL;
+struct emcmot_config_t *emcmotConfig = NULL;
+struct emcmot_internal_t *emcmotInternal = NULL;
+struct emcmot_error_t *emcmotError = NULL;
 
 static int mot_comp_id;
 
@@ -85,11 +85,11 @@ static int init_comm_buffers(void) {
     rtapi_print_msg(RTAPI_MSG_INFO,
 	"MOTION: init_comm_buffers() starting...\n");
 
-    emcmotStruct = 0;
-    emcmotInternal = 0;
-    emcmotStatus = 0;
-    c = 0;
-    emcmotConfig = 0;
+    emcmotStruct = NULL;
+    emcmotInternal = NULL;
+    emcmotStatus = NULL;
+    c = NULL;
+    emcmotConfig = NULL;
 
     /* allocate and initialize the shared memory structure */
     shmem_id = rtapi_shmem_new(DEFAULT_SHMEM_KEY, mot_comp_id, sizeof(emcmot_struct_t));

src/emc/motion/dbuf.c

@@ -187,7 +187,7 @@ int dbuf_get_string(dbuf_iter *di, const char **s) {
     // NUL, but let's be safe and not return a string if there's no terminated
     // string in the dbuf
     if(ch != 0) {
-        *s = 0;
+        *s = NULL;
         return -EAGAIN;
     }
 

src/emc/motion/emcmotutil.c

@@ -35,7 +35,7 @@
 
 int emcmotErrorInit(emcmot_error_t * errlog)
 {
-    if (errlog == 0) {
+    if (errlog == NULL) {
 	return -1;
     }
 
@@ -53,7 +53,7 @@ int emcmotErrorPutfv(emcmot_error_t * errlog, const char *fmt, va_list ap)
     struct dbuf_iter it;
     unsigned long long my_seq;
 
-    if (errlog == 0) {
+    if (errlog == NULL) {
 	return -1;
     }
 
@@ -108,7 +108,7 @@ int emcmotErrorGet(emcmot_error_t * errlog, char *error)
     unsigned long long w_res;
     unsigned long long w_com;
 
-    if (errlog == 0) {
+    if (errlog == NULL) {
 	return -1;
     }
 

src/emc/motion/usrmotintf.cc

@@ -40,12 +40,12 @@ using namespace linuxcnc;
 
 static int inited = 0;		/* flag if inited */
 
-static emcmot_command_t *emcmotCommand = 0;
-static emcmot_status_t *emcmotStatus = 0;
-static emcmot_config_t *emcmotConfig = 0;
-static emcmot_internal_t *emcmotInternal = 0;
-static emcmot_error_t *emcmotError = 0;
-static emcmot_struct_t *emcmotStruct = 0;
+static emcmot_command_t *emcmotCommand = NULL;
+static emcmot_status_t *emcmotStatus = NULL;
+static emcmot_config_t *emcmotConfig = NULL;
+static emcmot_internal_t *emcmotInternal = NULL;
+static emcmot_error_t *emcmotError = NULL;
+static emcmot_struct_t *emcmotStruct = NULL;
 
 /* usrmotIniLoad() loads params (SHMEM_KEY, COMM_TIMEOUT)
    from named INI file */
@@ -89,7 +89,7 @@ int usrmotWriteEmcmotCommand(emcmot_command_t * c)
     c->commandNum = ++commandNum;
 
     /* check for mapped mem still around */
-    if (0 == emcmotCommand) {
+    if (NULL == emcmotCommand) {
         rcs_print("USRMOT: ERROR: can't connect to shared memory\n");
 	return EMCMOT_COMM_ERROR_CONNECT;
     }
@@ -126,7 +126,7 @@ int usrmotReadEmcmotStatus(emcmot_status_t * s)
     int split_read_count;
 
     /* check for shmem still around */
-    if (0 == emcmotStatus) {
+    if (NULL == emcmotStatus) {
 	return EMCMOT_COMM_ERROR_CONNECT;
     }
     split_read_count = 0;
@@ -152,7 +152,7 @@ int usrmotReadEmcmotConfig(emcmot_config_t * s)
     int split_read_count;
 
     /* check for shmem still around */
-    if (0 == emcmotConfig) {
+    if (NULL == emcmotConfig) {
 	return EMCMOT_COMM_ERROR_CONNECT;
     }
     split_read_count = 0;
@@ -177,7 +177,7 @@ int usrmotReadEmcmotInternal(emcmot_internal_t * s)
     int split_read_count;
 
     /* check for shmem still around */
-    if (0 == emcmotInternal) {
+    if (NULL == emcmotInternal) {
 	return EMCMOT_COMM_ERROR_CONNECT;
     }
     split_read_count = 0;
@@ -200,7 +200,7 @@ int usrmotReadEmcmotInternal(emcmot_internal_t * s)
 int usrmotReadEmcmotError(char *e)
 {
     /* check to see if ptr still around */
-    if (emcmotError == 0) {
+    if (emcmotError == NULL) {
 	return -1;
     }
 
@@ -609,10 +609,10 @@ int usrmotExit(void)
 	rtapi_exit(module_id);
     }
 
-    emcmotStruct = 0;
-    emcmotCommand = 0;
-    emcmotStatus = 0;
-    emcmotError = 0;
+    emcmotStruct = NULL;
+    emcmotCommand = NULL;
+    emcmotStatus = NULL;
+    emcmotError = NULL;
 /*! \todo Another #if 0 */
 #if 0
 /*! \todo FIXME - comp structs no longer in shmem */

src/emc/pythonplugin/python_plugin.cc

@@ -291,8 +291,8 @@ PythonPlugin::PythonPlugin(struct _inittab *inittab) :
     status(0),
     module_mtime(0),
     reload_on_change(0),
-    toplevel(0),
-    abs_path(0),
+    toplevel(NULL),
+    abs_path(NULL),
     log_level(0)
 {
   PyConfig config;

src/emc/rs274ngc/canonmodule.cc

@@ -36,6 +36,8 @@ static void wrap_canon_error(const char *s)
 }
 
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
 BOOST_PYTHON_MODULE(emccanon) {
     using namespace boost::python;
     scope().attr("__doc__") =
@@ -269,3 +271,4 @@ BOOST_PYTHON_MODULE(emccanon) {
     def("GET_EXTERNAL_OFFSETS",&GET_EXTERNAL_OFFSETS);
 
 }
+#pragma GCC diagnostic pop

src/emc/rs274ngc/gcodemodule.cc

@@ -120,6 +120,8 @@ static PyMemberDef LineCodeMembers[] = {
     {}
 };
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
 static PyTypeObject LineCodeType = {
     PyVarObject_HEAD_INIT(NULL, 0)
     "gcode.linecode",       /*tp_name*/
@@ -180,6 +182,7 @@ static PyTypeObject LineCodeType = {
 #endif
 #endif
 };
+#pragma GCC diagnostic pop
 
 static PyObject *callback;
 static int interp_error;
@@ -854,8 +857,8 @@ void SET_NAIVECAM_TOLERANCE(double /*tolerance*/) { }
 #define RESULT_OK (result == INTERP_OK || result == INTERP_EXECUTE_FINISH)
 static PyObject *parse_file(PyObject * /*self*/, PyObject *args) {
     char *f;
-    char *unitcode=0, *initcode=0, *interpname=0;
-    PyObject *initcodes=0;
+    char *unitcode=NULL, *initcode=NULL, *interpname=NULL;
+    PyObject *initcodes=NULL;
     int error_line_offset = 0;
     struct timeval t0, t1;
     int wait = 1;
@@ -872,7 +875,7 @@ static PyObject *parse_file(PyObject * /*self*/, PyObject *args) {
 
     if(pinterp) {
         delete pinterp;
-        pinterp = 0;
+        pinterp = NULL;
     }
     if(interpname && *interpname)
         pinterp = interp_from_shlib(interpname);