diff --git a/ChangeLog b/ChangeLog
index da04e8477..877815674 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2010-11-19  Robert Larice
+ * */** :
+    Nr 4/5 (x = ...) != NULL , swallow warnings
+
 2010-11-19  Robert Larice
  * */** :
     Nr 3/5 (x = ...) != 0 , swallow warnings
diff --git a/src/frontend/com_compose.c b/src/frontend/com_compose.c
index 897e63def..5e888f23f 100644
--- a/src/frontend/com_compose.c
+++ b/src/frontend/com_compose.c
@@ -212,7 +212,7 @@ com_compose(wordlist *wl)
     } else {
         /* Parse the line... */
         while (wl) {
-            if ((s =strchr(wl->wl_word, '=')) && s[1]) {
+            if ((s = strchr(wl->wl_word, '=')) != NULL && s[1]) {
                 /* This is var=val. */
                 *s = '\0';
                 var = wl->wl_word;
diff --git a/src/frontend/com_history.c b/src/frontend/com_history.c
index c7f7c3d30..29cb8f535 100644
--- a/src/frontend/com_history.c
+++ b/src/frontend/com_history.c
@@ -124,7 +124,7 @@ dohsubst(char *string)
 
             case '?':
             (void) strcpy(buf, string + 1);
-            if ((s =strchr(buf, '?')))
+            if ((s = strchr(buf, '?')) != NULL)
                 *s = '\0';
             wl = hpattern(buf);
             if (!wl)
diff --git a/src/frontend/com_let.c b/src/frontend/com_let.c
index 99ca8b860..bd41a127d 100644
--- a/src/frontend/com_let.c
+++ b/src/frontend/com_let.c
@@ -37,14 +37,14 @@ com_let(wordlist *wl)
 
     /* extract indices */
     numdims = 0;
-    if ((rhs =strchr(p, '='))) {
+    if ((rhs = strchr(p, '=')) != NULL) {
 	*rhs++ = 0;
     } else {
 	fprintf(cp_err, "Error: bad let syntax\n");
 	tfree(p);
 	return;
     }
-    if ((s =strchr(p, '['))) {
+    if ((s = strchr(p, '[')) != NULL) {
 	need_open = 0;
 	*s++ = 0;
 	while (!need_open || *s == '[') {
diff --git a/src/frontend/com_measure2.c b/src/frontend/com_measure2.c
index 8e98e30b3..ee174638e 100644
--- a/src/frontend/com_measure2.c
+++ b/src/frontend/com_measure2.c
@@ -65,7 +65,7 @@ measure_get_precision(void)
    char *env_ptr;
    int  precision = 5;
 
-   if ( ( env_ptr = getenv("NGSPICE_MEAS_PRECISION") ) ) {
+   if (( env_ptr = getenv("NGSPICE_MEAS_PRECISION")) != NULL) {
       precision = atoi(env_ptr);
    }
 
diff --git a/src/frontend/cpitf.c b/src/frontend/cpitf.c
index 7909ddbee..4cc023a1d 100644
--- a/src/frontend/cpitf.c
+++ b/src/frontend/cpitf.c
@@ -247,7 +247,7 @@ ft_cpinit(void)
             /* add "spinit" to buf after actual position */
             (void) strcat(r, "spinit");
 #endif
-            if ((fp = fopen(buf, "r"))) {
+            if ((fp = fopen(buf, "r")) != NULL) {
                 cp_interactive = FALSE;
                 inp_spsource(fp, TRUE, buf);
                 cp_interactive = TRUE;
@@ -255,7 +255,7 @@ ft_cpinit(void)
                 break;
 #if defined (HAS_WINDOWS) || defined (__MINGW32__) || defined (_MSC_VER)
             /* search in local directory where ngspice.exe resides */
-            } else if ((fp = fopen("./spinit", "r"))) {
+            } else if ((fp = fopen("./spinit", "r")) != NULL) {
                 cp_interactive = FALSE;
                 inp_spsource(fp, TRUE, buf);
                 cp_interactive = TRUE;
@@ -348,7 +348,7 @@ cp_oddcomm(char *s, wordlist *wl)
     char buf[BSIZE_SP];
     wordlist ww;
 
-    if ((fp = inp_pathopen(s, "r"))) {
+    if ((fp = inp_pathopen(s, "r")) != NULL) {
         (void) fclose(fp);
         (void) sprintf(buf, "argc = %d argv = ( ", wl_length(wl));
         while (wl) {
diff --git a/src/frontend/dotcards.c b/src/frontend/dotcards.c
index 3ee81c4ef..fbd3a6ea9 100644
--- a/src/frontend/dotcards.c
+++ b/src/frontend/dotcards.c
@@ -540,7 +540,7 @@ gettoks(char *s)
     prevp = &list;
 
     if (strstr( s, "(" )) s = stripWhiteSpacesInsideParens(s);
-    while ((t = gettok(&s))) {
+    while ((t = gettok(&s)) != NULL) {
 	if (*t == '(')
 	    continue;
 	l =strrchr(t, '('/*)*/);
diff --git a/src/frontend/help/readhelp.c b/src/frontend/help/readhelp.c
index 4a40d0924..26aed8c61 100644
--- a/src/frontend/help/readhelp.c
+++ b/src/frontend/help/readhelp.c
@@ -129,7 +129,7 @@ endtext:
         s = &buf[10];
         /* process tokens within line, updating pointer */
 	while (*s) {
-          if ((topiclink = getsubtoplink(&s))) {
+          if ((topiclink = getsubtoplink(&s)) != NULL) {
             if (tend)
               tend->next = topiclink;
             else
@@ -146,7 +146,7 @@ endtext:
         s = &buf[9];
         /* process tokens within line, updating pointer */
 	while (*s) {
-          if ((topiclink = getsubtoplink(&s))) {
+          if ((topiclink = getsubtoplink(&s)) != NULL) {
             if (tend)
               tend->next = topiclink;
             else
@@ -186,7 +186,7 @@ static toplink *getsubtoplink(char **ss)
     s = *ss;
 
     tl = alloc(toplink);
-    if ((tmp =strchr(s, ':'))) {
+    if ((tmp =strchr(s, ':')) != NULL) {
       tl->place = alloc(fplace);
       tl->place->filename = strncpy(
             TMALLOC(char, tmp - s + 1),
diff --git a/src/frontend/inpcom.c b/src/frontend/inpcom.c
index e096dc29b..1e0c8e104 100644
--- a/src/frontend/inpcom.c
+++ b/src/frontend/inpcom.c
@@ -189,7 +189,7 @@ inp_pathopen(char *name, char *mode)
        /* add file name */
        strcat(buf2, name);
        /* try to open file */
-       if ((fp = fopen(buf2, mode)))
+       if ((fp = fopen(buf2, mode)) != NULL)
           return (fp);
     }
 #endif
@@ -219,7 +219,7 @@ inp_pathopen(char *name, char *mode)
                 controlled_exit(EXIT_FAILURE);
             }
         }
-        if ((fp = fopen(buf, mode)))
+        if ((fp = fopen(buf, mode)) != NULL)
             return (fp);
         v = v->va_next;
     }
@@ -238,7 +238,7 @@ inp_fix_gnd_name( struct line *deck ) {
     // if there is a comment or no gnd, go to next line
     if (( *gnd == '*' ) || (strstr( gnd, "gnd" ) == NULL)) { c = c->li_next; continue; }
     // replace "§gnd§" by "§ 0 §", § being a ' '  ','  '('  ')'.
-	while ( (gnd = strstr( gnd, "gnd" ) ) ) {
+	while ((gnd = strstr( gnd, "gnd" )) != NULL) {
       if (( isspace(*(gnd-1)) || *(gnd-1) == '(' || *(gnd-1) == ','  ) &&
          ( isspace(*(gnd+3)) || *(gnd+3) == ')' || *(gnd+3) == ','  ))
       {
@@ -278,10 +278,10 @@ inp_chk_for_multi_in_vcvs( struct line *deck, int *line_number ) {
     for ( c = deck; c != NULL; c = c->li_next ) {
         str_ptr1 = line = c->li_line;
         if ( *line == 'e' ) {
-            if ( (bool_ptr = strstr( line, "nand(" )) ||
-              (bool_ptr = strstr( line, "and("  )) ||
-              (bool_ptr = strstr( line, "nor("  )) ||
-              (bool_ptr = strstr( line, "or("   )) ) {
+            if ( (bool_ptr = strstr( line, "nand(" )) != NULL ||
+              (bool_ptr = strstr( line, "and("  )) != NULL ||
+              (bool_ptr = strstr( line, "nor("  )) != NULL ||
+              (bool_ptr = strstr( line, "or("   )) != NULL ) {
                 while ( !isspace(*str_ptr1) ) str_ptr1++;
                 keep = *str_ptr1;	
 				*str_ptr1  = '\0';
@@ -539,7 +539,7 @@ get_instance_subckt( char *line )
   char keep = ' ';
 
   // see if instance has parameters
-  if ( ( equal_ptr = strstr( line, "=" ) ) ) {
+  if ((equal_ptr = strstr(line, "=")) != NULL) {
     end_ptr = equal_ptr - 1;
     while ( isspace(*end_ptr)  ) end_ptr--;
     while ( !isspace(*end_ptr) ) end_ptr--;
@@ -718,7 +718,7 @@ model_bin_match( char* token, char* model_name )
   bool  flag = FALSE;
 
   if ( strncmp( model_name, token, strlen(token) ) == 0 ) {
-    if ( (dot_char = strstr( model_name, "." )) ) {
+    if ((dot_char = strstr( model_name, "." )) != NULL) {
       flag = TRUE;
       dot_char++;
       while( *dot_char != '\0' ) {
@@ -951,7 +951,7 @@ inp_fix_ternary_operator_str( char *line )
     str_ptr2 = colon - 1;
     while ( isspace(*str_ptr2) ) str_ptr2--;	
   }
-  else if ( ( colon = strstr( str_ptr, ":" ) ) ) {
+  else if ((colon = strstr( str_ptr, ":" )) != NULL) {
     str_ptr2 = colon - 1;
     while ( isspace(*str_ptr2) ) str_ptr2--;
   }
@@ -992,7 +992,7 @@ inp_fix_ternary_operator_str( char *line )
     *str_ptr2 = keep;
   }
   else {
-    if ( ( str_ptr2 = strstr( str_ptr, "}" ) ) ) {
+    if ((str_ptr2 = strstr(str_ptr, "}")) != NULL) {
       *str_ptr2 = '\0';
       else_str = inp_fix_ternary_operator_str(strdup(str_ptr));
       *str_ptr2 = '}';
@@ -1147,7 +1147,7 @@ inp_readall(FILE *fp, struct line **data, int call_depth, char *dir_name, bool c
 
 /* gtri - end - 12/12/90 */
 #else
-   while ((buffer = readline(fp))) {
+   while ((buffer = readline(fp)) != NULL) {
 #endif
 
 #ifdef TRACE
@@ -1402,7 +1402,7 @@ inp_readall(FILE *fp, struct line **data, int call_depth, char *dir_name, bool c
       end->li_linenum = line_number++;
       end->li_linenum_orig = line_number_orig++;
       tfree(buffer);
-   }  /* end while ((buffer = readline(fp))) */
+   }  /* end while ((buffer = readline(fp)) != NULL) */
 
    if (!end) { /* No stuff here */
       *data = NULL;
@@ -1849,7 +1849,7 @@ inp_fix_subckt( char *s )
 
     head = alloc(struct line);
     /* create list of parameters that need to get sorted */
-    while ( *beg && (ptr1 = strstr( beg, "=" ) ) ) {
+    while ( *beg && (ptr1 = strstr( beg, "=" )) != NULL ) {
       ptr2 = ptr1+1;
       ptr1--;
       while ( isspace(*ptr1)  ) ptr1--;
@@ -2131,7 +2131,7 @@ inp_get_params( char *line, char *param_names[], char *param_values[] )
   char keep;
   bool is_expression = FALSE;
 
-  while ( ( equal_ptr = strstr( line, "=" ) ) ) {
+  while ( (equal_ptr = strstr( line, "=" )) != NULL ) {
 
     // check for equality '=='
     if ( *(equal_ptr+1) == '=' ) { line = equal_ptr+2; continue; }
@@ -2534,7 +2534,7 @@ inp_do_macro_param_replace( int fcn_number, char *params[] )
       search_ptr = curr_ptr = curr_str;
       curr_str = NULL;
     }
-    while ( ( param_ptr = strstr( search_ptr, func_params[fcn_number][i] ) ) ) {
+    while ((param_ptr = strstr( search_ptr, func_params[fcn_number][i] ) ) != NULL ) {
 
       /* make sure actually have the parameter name */
       if (param_ptr == search_ptr) /* no valid 'before' */
@@ -2600,7 +2600,7 @@ inp_expand_macro_in_str( char *str )
    char *orig_ptr = str, *search_ptr = str, *orig_str = strdup(str);
    char keep;
 
-   while ( ( open_paren_ptr = strstr( search_ptr, "(" ) ) ) {
+   while ( (open_paren_ptr = strstr( search_ptr, "(" )) != NULL ) {
       fcn_name = open_paren_ptr;
       if ( open_paren_ptr != search_ptr) {
          while ( --fcn_name != search_ptr && (isalnum(*fcn_name) || *fcn_name == '_') )
@@ -2793,7 +2793,7 @@ inp_fix_param_values( struct line *deck )
     /* exclude CIDER devices with ic.file parameter */
     if ( strstr(line, "ic.file")) { c = c->li_next; continue; }
 
-    while ( ( equal_ptr = strstr( line, "=" ) ) ) {
+    while ((equal_ptr = strstr( line, "=" )) != NULL ) {
 
       // special case: .MEASURE {DC|AC|TRAN} result FIND out_variable WHEN out_variable2=out_variable3
       // no braces around out_variable3. out_variable3 may be v(...) or i(...) 
@@ -2974,7 +2974,7 @@ get_param_name( char *line )
   char *name = NULL, *equal_ptr, *beg;
   char keep;
 
-  if ( ( equal_ptr = strstr( line, "=" ) ) )
+  if (( equal_ptr = strstr( line, "=" ) ) != NULL )
     {
       equal_ptr--;
       while ( isspace(*equal_ptr)  ) equal_ptr--;
@@ -3001,7 +3001,7 @@ get_param_str( char *line )
 {
   char *equal_ptr;
 
-  if ( ( equal_ptr = strstr( line, "=" ) ) ) {
+  if (( equal_ptr = strstr( line, "=" ) ) != NULL ) {
     equal_ptr++;
     while ( isspace(*equal_ptr) ) equal_ptr++;
     return equal_ptr;
@@ -3089,7 +3089,7 @@ get_number_terminals( char *c )
       name[i] = gettok_instance(&c);
       if (strstr(name[i], "off") || strstr(name[i], "=")) j++;
       /* If we have IC=VBE, VCE instead of IC=VBE,VCE we need to inc j */
-      if ((comma = strstr(name[i], ",")) && ( *(++comma) == '\0')) j++;
+      if ((comma = strstr(name[i], ",")) != NULL && ( *(++comma) == '\0')) j++;
       /* If we have IC=VBE , VCE ("," is a token) we need to inc j */
       if (eq(name[i], ",")) j++;
       i++;
@@ -3218,7 +3218,7 @@ inp_sort_params( struct line *start_card, struct line *end_card, struct line *ca
 
           param_str = param_strs[j];
 
-          while ( ( param_ptr = strstr( param_str, param_name ) ) )
+          while ((param_ptr = strstr( param_str, param_name ) ) != NULL )
           {  
             ioff = (strstr(param_ptr, "}") != NULL ? 1 : 0);  /* want prevent wrong memory access below */
             /* looking for curly braces or other string limiter */
@@ -3274,7 +3274,7 @@ inp_sort_params( struct line *start_card, struct line *end_card, struct line *ca
 	      while ( isspace(*str_ptr)  && *str_ptr != '\0' ) str_ptr++;
 	    }
 
-	  while ( ( str_ptr = strstr( str_ptr, param_names[i] ) ) )
+	  while ((str_ptr = strstr( str_ptr, param_names[i] ) ) != NULL )
 	    {
 	      /* make sure actually have the parameter name */
 	      char before = *(str_ptr-1);
@@ -3475,7 +3475,7 @@ inp_split_multi_param_lines( struct line *deck, int line_num )
       if ( ciprefix( ".param", curr_line ) )
 	{
 	  counter = 0;
-	  while ( ( equal_ptr = strstr( curr_line, "=" ) ) ) {
+	  while (( equal_ptr = strstr( curr_line, "=" ) ) != NULL ) {
 	    // check for equality '=='
 	    if ( *(equal_ptr+1) == '=' ) { curr_line = equal_ptr+2; continue; }
 	    // check for '!=', '<=', '>='
@@ -3487,7 +3487,7 @@ inp_split_multi_param_lines( struct line *deck, int line_num )
 	  // need to split multi param line
 	  curr_line = card->li_line;
 	  counter   = 0;
-	  while ( curr_line < card->li_line+strlen(card->li_line) && ( equal_ptr = strstr( curr_line, "=" ) ) )
+	  while ( curr_line < card->li_line+strlen(card->li_line) && ( equal_ptr = strstr( curr_line, "=" ) ) != NULL )
 	    {
 	      // check for equality '=='
 	      if ( *(equal_ptr+1) == '=' ) { curr_line = equal_ptr+2; continue; }
diff --git a/src/frontend/measure.c b/src/frontend/measure.c
index 075d969b5..e8cd55773 100644
--- a/src/frontend/measure.c
+++ b/src/frontend/measure.c
@@ -83,7 +83,7 @@ com_meas(wordlist *wl) {
          } 
       } 
 	   /* may be inside the same wl_word */
-      else if ( (equal_ptr = strstr( token, "=" )) ) {
+      else if ( (equal_ptr = strstr( token, "=" )) != NULL ) {
          vec_found = equal_ptr + 1;
          if (!cieq(vec_found, "LAST")) {
             INPevaluate( &vec_found, &err, 1 );
@@ -162,7 +162,7 @@ get_double_value(
 
       *value = INPevaluate( &junk, &err, 1 );
     } else {
-      if ( (equal_ptr = strstr( token, "=" )) ) {
+      if ( (equal_ptr = strstr( token, "=" )) != NULL ) {
 	equal_ptr += 1;
 	*value = INPevaluate( &equal_ptr, &err, 1 );
       } else {
diff --git a/src/frontend/newcoms.c b/src/frontend/newcoms.c
index 3bd5bd7f0..93975db26 100644
--- a/src/frontend/newcoms.c
+++ b/src/frontend/newcoms.c
@@ -45,7 +45,7 @@ com_reshape(wordlist *wl)
 
 	p = NULL;
 	for (w = wl; w; w = w->wl_next) {
-	  if ((p =strchr(w->wl_word, '[')))
+	  if ((p = strchr(w->wl_word, '[')) != NULL)
 		    break;
 	}
 
@@ -210,5 +210,5 @@ com_reshape(wordlist *wl)
 	    if (vname)
 	        tfree(vname);
 	}
-    } while ((wl = wlast));
+    } while ((wl = wlast) != NULL);
 }
diff --git a/src/frontend/numparam/mystring.c b/src/frontend/numparam/mystring.c
index ea0d4fdef..d9fcb4f70 100644
--- a/src/frontend/numparam/mystring.c
+++ b/src/frontend/numparam/mystring.c
@@ -865,7 +865,7 @@ spos_(char *sub, char *s)
 {
   char *ptr;
 
-  if ((ptr = strstr (s, sub)))
+  if ((ptr = strstr (s, sub)) != NULL)
     return (int) (strlen (s) - strlen (ptr));
   else
     return -1 ;
diff --git a/src/frontend/numparam/xpressn.c b/src/frontend/numparam/xpressn.c
index 6291767ff..544ed1736 100644
--- a/src/frontend/numparam/xpressn.c
+++ b/src/frontend/numparam/xpressn.c
@@ -2263,7 +2263,7 @@ nupa_subcktcall (tdico * dico, char *s, char *x, bool err)
       token = strtok(buf, " ");       /* a bit more exact - but not sufficient everytime */
       j = j + (int) strlen(token) + 1;
       if (strcmp(token, spice_dstring_value(&subname))) {
-        while ((token = strtok(NULL, " "))) {
+        while ((token = strtok(NULL, " ")) != NULL) {
           if (!strcmp(token, spice_dstring_value(&subname))) {
             found = 1;
             break;
diff --git a/src/frontend/options.c b/src/frontend/options.c
index 96cffe3b7..04f3f5df3 100644
--- a/src/frontend/options.c
+++ b/src/frontend/options.c
@@ -155,23 +155,23 @@ cp_usrvars(struct variable **v1, struct variable **v2)
         v =  plot_cur->pl_env;
     else
         v = NULL;
-    if ((tv = cp_enqvar("plots"))) {
+    if ((tv = cp_enqvar("plots")) != NULL) {
         tv->va_next = v;
         v = tv;
     }
-    if ((tv = cp_enqvar("curplot"))) {
+    if ((tv = cp_enqvar("curplot")) != NULL) {
         tv->va_next = v;
         v = tv;
     }
-    if ((tv = cp_enqvar("curplottitle"))) {
+    if ((tv = cp_enqvar("curplottitle")) != NULL) {
         tv->va_next = v;
         v = tv;
     }
-    if ((tv = cp_enqvar("curplotname"))) {
+    if ((tv = cp_enqvar("curplotname")) != NULL) {
         tv->va_next = v;
         v = tv;
     }
-    if ((tv = cp_enqvar("curplotdate"))) {
+    if ((tv = cp_enqvar("curplotdate")) != NULL) {
         tv->va_next = v;
         v = tv;
     }
diff --git a/src/frontend/outitf.c b/src/frontend/outitf.c
index 892fc05d3..86ce22500 100644
--- a/src/frontend/outitf.c
+++ b/src/frontend/outitf.c
@@ -815,7 +815,7 @@ fileInit_pass2(runDesc *run)
  
         if ( type == SV_CURRENT ) {
           branch = NULL;
-          if ( (branch = strstr( name, "#branch" )) ) {
+          if ( (branch = strstr( name, "#branch" )) != NULL ) {
             *branch = '\0';
           }
           fprintf(run->fp, "\t%d\ti(%s)\t%s", i, name, ft_typenames(type));
@@ -1089,14 +1089,14 @@ name_eq(char *n1, char *n2)
 {
     char buf1[BSIZE_SP], buf2[BSIZE_SP], *s;
 
-    if ((s =strchr(n1, '('))) {
+    if ((s =strchr(n1, '(')) != NULL) {
         strcpy(buf1, s);
         if (!(s =strchr(buf1, ')')))
             return FALSE;
         *s = '\0';
         n1 = buf1;
     }
-    if ((s =strchr(n2, '('))) {
+    if ((s =strchr(n2, '(')) != NULL) {
         strcpy(buf2, s);
         if (!(s =strchr(buf2, ')')))
             return FALSE;
@@ -1119,7 +1119,7 @@ getSpecial(dataDesc *desc, runDesc *run, IFvalue *val)
             &selector) == OK) {
       desc->type &= (IF_REAL | IF_COMPLEX);   /* mask out other bits */
       return TRUE;
-    } else if ((vv = if_getstat(run->circuit, &desc->name[1]))) {
+    } else if ((vv = if_getstat(run->circuit, &desc->name[1])) != NULL) {
 						/* skip @ sign */
       desc->type = IF_REAL;
       if (vv->va_type == CP_REAL)
diff --git a/src/frontend/parser/complete.c b/src/frontend/parser/complete.c
index e0d89b65a..3f81025eb 100644
--- a/src/frontend/parser/complete.c
+++ b/src/frontend/parser/complete.c
@@ -215,7 +215,7 @@ ccfilec(char *buf)
         lcomp = buf;
         if (*buf == cp_til) {   /* User name completion... */
             buf++;
-            while ((pw = getpwent())) {
+            while ((pw = getpwent()) != NULL) {
                 if (prefix(buf, pw->pw_name)) {
                     if (wl == NULL) {
                         wl = alloc(struct wordlist);
@@ -246,7 +246,7 @@ ccfilec(char *buf)
     }
     if (!(wdir = opendir(dir)))
         return (NULL);
-    while ((de = readdir(wdir)))
+    while ((de = readdir(wdir)) != NULL)
         if ((prefix(lcomp, de->d_name)) && (*lcomp ||
                 (*de->d_name != '.'))) {
             if (wl == NULL) {
diff --git a/src/frontend/plotting/graf.c b/src/frontend/plotting/graf.c
index be4cbe45d..6e29b3bbc 100644
--- a/src/frontend/plotting/graf.c
+++ b/src/frontend/plotting/graf.c
@@ -279,7 +279,7 @@ gr_point(struct dvec *dv,
 	   want to connect with oldx and oldy. */
 	if (np)
 	    DevDrawLine(fromx, fromy, tox, toy);
-	if ((tics = (double *) currentgraph->ticdata)) {
+	if ((tics = (double *) currentgraph->ticdata) != NULL) {
 	    for (; *tics < HUGE; tics++) {
 		if (*tics == (double) np) {
 		    DevDrawText("x", (int) (tox - currentgraph->fontwidth / 2),
diff --git a/src/frontend/plotting/grid.c b/src/frontend/plotting/grid.c
index e67348bb7..4fc2e2baa 100644
--- a/src/frontend/plotting/grid.c
+++ b/src/frontend/plotting/grid.c
@@ -350,7 +350,7 @@ lingrid(GRAPH *graph, double lo, double hi, double delta, int type, Axis axis)
 	(void) sprintf(buf, "x10^%d ", mag);
     }
 
-    if ((s = ft_typabbrev(type))) {
+    if ((s = ft_typabbrev(type)) != NULL) {
 	(void) strcat(buf, s);
     } else {
 	(void) strcat(buf, "Units");
@@ -612,7 +612,7 @@ loggrid(GRAPH *graph, double lo, double hi, int type, Axis axis)
     dd[0] = pow(10.0, (double) lmt);
     dd[1] = pow(10.0, (double) hmt);
 
-    if ((s = ft_typabbrev(type))) {
+    if ((s = ft_typabbrev(type)) != NULL) {
 	(void) strcpy(buf, s);
     } else {
 	(void) strcpy(buf, "Units");
diff --git a/src/frontend/plotting/x11.c b/src/frontend/plotting/x11.c
index 9b69c5f1f..60e028391 100644
--- a/src/frontend/plotting/x11.c
+++ b/src/frontend/plotting/x11.c
@@ -812,7 +812,7 @@ zoomin(GRAPH *graph)
     }
 
     strncpy(buf2, graph->plotname, sizeof(buf2));
-    if ((t =strchr(buf2, ':')))
+    if ((t = strchr(buf2, ':')) != NULL)
 	    *t = 0;
 
     if (!eq(plot_cur->pl_typename, buf2)) {
diff --git a/src/frontend/rawfile.c b/src/frontend/rawfile.c
index 7072f4061..c9365977a 100644
--- a/src/frontend/rawfile.c
+++ b/src/frontend/rawfile.c
@@ -157,7 +157,7 @@ raw_write(char *name, struct plot *pl, bool app, bool binary)
     for (i = 0, v = pl->pl_dvecs; v; v = v->v_next) {
       if ( strcmp( ft_typenames(v->v_type), "current" ) == 0 ) {
 	branch = NULL;
-	if ( (branch = strstr( v->v_name, "#branch" )) ) {
+	if ((branch = strstr( v->v_name, "#branch" )) != NULL) {
 	  *branch = '\0';
 	}
         fprintf(fp, "\t%d\ti(%s)\t%s", i++, v->v_name, ft_typenames(v->v_type));
@@ -372,7 +372,7 @@ raw_read(char *name)
         } else if (ciprefix("flags:", buf)) {
             s = buf;
             skip(s);
-            while ((t = gettok(&s))) {
+            while ((t = gettok(&s)) != NULL) {
                 if (cieq(t, "real"))
                     flags |= VF_REAL;
                 else if (cieq(t, "complex"))
@@ -497,7 +497,7 @@ raw_read(char *name)
                     s = buf;
                 }
                 (void) gettok(&s);  /* The strchr field. */
-                if ((t = gettok(&s)))
+                if ((t = gettok(&s)) != NULL)
                     v->v_name = t;
                 else {
                     fprintf(cp_err, 
@@ -516,13 +516,13 @@ raw_read(char *name)
                 
                 /* Fix the name... */
                 if (isdigit(*v->v_name) && (r = ft_typabbrev(v
-                        ->v_type))) {
+                        ->v_type)) != NULL) {
                     (void) sprintf(buf2, "%s(%s)", r,
                             v->v_name);
                     v->v_name = copy(buf2);
                 }
                 /* Now come the strange options... */
-                while ((t = gettok(&s))) {
+                while ((t = gettok(&s)) != NULL) {
                     if (ciprefix("min=", t)) {
                         if (sscanf(t + 4, "%lf",
                             &v->v_minsignal) != 1)
diff --git a/src/frontend/subckt.c b/src/frontend/subckt.c
index a2c90b5ab..de7188382 100644
--- a/src/frontend/subckt.c
+++ b/src/frontend/subckt.c
@@ -899,7 +899,7 @@ translate(struct line *deck, char *formal, char *actual, char *scname, char *sub
 
         if ( ciprefix( ".ic", c->li_line ) || ciprefix( ".nodeset", c->li_line ) ) {
             paren_ptr = s = c->li_line;
-            while ( ( paren_ptr = strstr( paren_ptr, "(" ) ) ) {
+            while ( ( paren_ptr = strstr( paren_ptr, "(" ) )  != NULL) {
                 *paren_ptr = '\0';
                 paren_ptr++;
                 name = paren_ptr;
@@ -1457,7 +1457,7 @@ model_bin_match( char* token, char* model_name )
    /* continue evaluation if toeken is part of model_name */ 
    if ( strncmp( model_name, token, strlen(token) ) == 0 ) {
       /* find last dot in model_name */
-      if ( (dot_char = strrchr( model_name, '.' )) ) {
+      if ( (dot_char = strrchr( model_name, '.' )) != NULL ) {
          flag = TRUE;
          dot_char++;
          while( *dot_char != '\0' ) {
@@ -1945,7 +1945,7 @@ devmodtranslate(struct line *deck, char *subname)
            for (wlsub = submod; wlsub; wlsub = wlsub->wl_next) {
                i = (int) strlen(wlsub->wl_word);
                j = 0; /* Now, have we a binned model? */
-               if ( (dot_char = strstr( wlsub->wl_word, "." )) ) {
+               if ( (dot_char = strstr( wlsub->wl_word, "." )) != NULL) {
                   dot_char++; j++;
                   while( *dot_char != '\0' ) {
                     if ( !isdigit( *dot_char ) ) {
diff --git a/src/frontend/terminal.c b/src/frontend/terminal.c
index 9efd23bf7..20375ea46 100644
--- a/src/frontend/terminal.c
+++ b/src/frontend/terminal.c
@@ -301,7 +301,7 @@ tcap_init(void)
 
     charbuf = buf2;
 
-    if ((s = getenv("TERM"))) {
+    if ((s = getenv("TERM")) != NULL) {
 	if (tgetent(tbuf, s) != -1) {
 	    xsize = tgetnum("co");
 	    ysize = tgetnum("li");
@@ -316,14 +316,14 @@ tcap_init(void)
 #endif
 
     if (!xsize) {
-        if ((s = getenv("COLS")))
+        if ((s = getenv("COLS")) != NULL)
             xsize = atoi(s);
         if (xsize <= 0)
             xsize = 0;
     }
 
     if (!ysize) {
-        if ((s = getenv("LINES")))
+        if ((s = getenv("LINES")) != NULL)
             ysize = atoi(s);
         if (ysize <= 0)
             ysize = 0;
diff --git a/src/frontend/variable.c b/src/frontend/variable.c
index db5f34e13..84ea090c9 100644
--- a/src/frontend/variable.c
+++ b/src/frontend/variable.c
@@ -298,7 +298,7 @@ cp_setparse(wordlist *wl)
         } else if (wl && (*wl->wl_word == '=')) {
             val = wl->wl_word + 1;
             wl = wl->wl_next;
-        } else if ((s =strchr(name, '='))) {
+        } else if ((s =strchr(name, '=')) != NULL) {
             val = s + 1;
             *s = '\0';
             if (*val == '\0') {
@@ -667,7 +667,7 @@ cp_variablesubst(wordlist *wlist)
     for (wl = wlist; wl; wl = wl->wl_next) {
         t = wl->wl_word;
         i = 0;
-        while ((s =strchr(t, cp_dol))) {
+        while ((s =strchr(t, cp_dol)) != NULL) {
             while (t < s)
                 wbuf[i++] = *t++;
             wbuf[i] = '\0';
@@ -732,7 +732,7 @@ vareval(char *string)
     int i, up, low;
 
     cp_wstrip(string);
-    if ((s =strchr(string, '['))) {
+    if ((s =strchr(string, '[')) != NULL) {
         *s = '\0';
         range = s + 1;
     }
@@ -830,7 +830,7 @@ vareval(char *string)
         string = oldstring;
         v = cp_enqvar(string);
     }
-    if (!v && (s = getenv(string))) {
+    if (!v && (s = getenv(string)) != NULL) {
         wl = alloc(struct wordlist);
         wl->wl_next = wl->wl_prev = NULL;
         wl->wl_word = copy(s);
diff --git a/src/frontend/wdisp/windisp.c b/src/frontend/wdisp/windisp.c
index 44604272c..f20291976 100644
--- a/src/frontend/wdisp/windisp.c
+++ b/src/frontend/wdisp/windisp.c
@@ -480,7 +480,7 @@ LRESULT CALLBACK PlotWindowProc( HWND hwnd,
       WIN_ScreentoData(gr, xe, ye, &fxe, &fye);
       
       strncpy(buf2, gr->plotname, sizeof(buf2));
-      if ((t = index(buf2, ':'))) /* strchr */
+      if ((t = index(buf2, ':')) != NULL) /* strchr */
          *t = 0;
 
       if (!eq(plot_cur->pl_typename, buf2)) {
diff --git a/src/maths/sparse/spsmp.c b/src/maths/sparse/spsmp.c
index c2a5497cb..ac7def851 100644
--- a/src/maths/sparse/spsmp.c
+++ b/src/maths/sparse/spsmp.c
@@ -424,7 +424,7 @@ LoadGmin(SMPmatrix *eMatrix, double Gmin)
     if (Gmin != 0.0) {
 	Diag = Matrix->Diag;
 	for (I = Matrix->Size; I > 0; I--) {
-	    if ((diag = Diag[I]))
+	    if ((diag = Diag[I]) != NULL)
 		diag->Real += Gmin;
 	}
     }
diff --git a/src/misc/hash.c b/src/misc/hash.c
index c8f301797..78a48f407 100644
--- a/src/misc/hash.c
+++ b/src/misc/hash.c
@@ -540,7 +540,7 @@ static NGTABLEPTR _nghash_find_item(NGHASHPTR htable,void * user_key,void * data
     }
 
     /* insert into table only if distinct number */
-    if( (temptr = table[hsum]) ){
+    if( (temptr = table[hsum]) != NULL ){
       /* list started at this hash */
       for(curPtr=temptr ; curPtr ; curPtr=curPtr->next ) {
 	if( htable->compare_func == (void *) NGHASH_DEF_CMP_STR ) {
@@ -574,14 +574,14 @@ void * nghash_enumeratek(NGHASHPTR htable, void * *key_return, BOOL start_flag)
     NGTABLEPTR current_spot ;	/* current place in threaded list */
 
     if( start_flag ){
-	if( (htable->enumeratePtr = htable->thread) ){
+	if( (htable->enumeratePtr = htable->thread) != NULL ) {
 	    current_spot = htable->enumeratePtr ;
 	    *key_return = current_spot->key ;
 	    return( current_spot->data ) ;
 	}
     } else {
 	if( htable->enumeratePtr && 
-	    (htable->enumeratePtr = htable->enumeratePtr->thread_next) ){
+	    (htable->enumeratePtr = htable->enumeratePtr->thread_next) != NULL ){
 	    current_spot = htable->enumeratePtr ;
 	    *key_return = current_spot->key ;
 	    return( current_spot->data ) ;
@@ -597,13 +597,13 @@ void * nghash_enumerate(NGHASHPTR htable,BOOL start_flag)
     NGTABLEPTR current_spot ;	/* current place in threaded list */
 
     if( start_flag ){
-	if( (htable->enumeratePtr = htable->thread) ){
+	if( (htable->enumeratePtr = htable->thread) != NULL ){
 	    current_spot = htable->enumeratePtr ;
 	    return( current_spot->data ) ;
 	}
     } else {
 	if( htable->enumeratePtr && 
-	    (htable->enumeratePtr = htable->enumeratePtr->thread_next) ){
+	    (htable->enumeratePtr = htable->enumeratePtr->thread_next) != NULL ){
 	    current_spot = htable->enumeratePtr ;
 	    return( current_spot->data ) ;
 	}
@@ -625,14 +625,14 @@ void * nghash_enumeratekRE(NGHASHPTR htable, void * *key_return, NGHASHITERPTR i
       return(NULL) ;
     }
     if(!(iter_p->position)){
-      if( (iter_p->position = htable->thread) ){
+      if( (iter_p->position = htable->thread) != NULL ){
 	current_spot = iter_p->position ;
 	*key_return = current_spot->key ;
 	return( current_spot->data ) ;
       }
     } else {
       if( iter_p->position && 
-	(iter_p->position = iter_p->position->thread_next) ){
+	(iter_p->position = iter_p->position->thread_next) != NULL ){
 	current_spot = iter_p->position ;
 	*key_return = current_spot->key ;
 	return( current_spot->data ) ;
@@ -656,13 +656,13 @@ void * nghash_enumerateRE(NGHASHPTR htable, NGHASHITERPTR iter_p)
       return(NULL) ;
     }
     if(!(iter_p->position)){
-      if( (iter_p->position = htable->thread) ){
+      if( (iter_p->position = htable->thread) != NULL ){
 	current_spot = iter_p->position ;
 	return( current_spot->data ) ;
       }
     } else {
       if( iter_p->position && 
-	(iter_p->position = iter_p->position->thread_next) ){
+	(iter_p->position = iter_p->position->thread_next) != NULL ){
 	current_spot = iter_p->position ;
 	return( current_spot->data ) ;
       }
@@ -716,7 +716,7 @@ void nghash_dump(NGHASHPTR htable, void (*print_key) (void *))
     fprintf( stderr, "Table is %4.2f%% full\n", 
 	100.0 * (double) htable->num_entries / (double) htable->size ) ;
     for( i = 0 ; i < htable->size ; i++ ) {
-	if( (hptr = table[i]) ){
+	if( (hptr = table[i]) != NULL ){
 	    fprintf( stderr, " [%5d]:", i ) ;
 	    count = 0 ;
 	    for( ; hptr ; hptr=hptr->next ){
diff --git a/src/misc/ivars.c b/src/misc/ivars.c
index 581c05b7f..4e3309875 100644
--- a/src/misc/ivars.c
+++ b/src/misc/ivars.c
@@ -26,7 +26,7 @@ static void
 env_overr(char **v, char *e)
 {
     char *p;
-    if (v && e && (p = getenv(e)))
+    if (v && e && (p = getenv(e)) != NULL)
         *v = p;
 }
 
diff --git a/src/misc/string.c b/src/misc/string.c
index c0b7fd792..e165aa2ba 100644
--- a/src/misc/string.c
+++ b/src/misc/string.c
@@ -28,7 +28,7 @@ copy(const char *str)
 {
     char *p;
     
-    if ((p = TMALLOC(char, strlen(str) + 1)))
+    if ((p = TMALLOC(char, strlen(str) + 1)) != NULL)
 	    (void) strcpy(p, str);
     return(p);
 }
@@ -39,7 +39,7 @@ copy_substring(const char *str, const char *end)
     size_t n = (size_t) (end - str);
     char *p;
 
-    if ((p = TMALLOC(char, n + 1))) {
+    if ((p = TMALLOC(char, n + 1)) != NULL) {
         (void) strncpy(p, str, n);
         p[n] = '\0';
     }
@@ -544,7 +544,7 @@ get_comma_separated_values( char *values[], char *str ) {
   int count = 0;
   char *ptr, *comma_ptr, keep;
   
-  while ( ( comma_ptr = strstr( str, "," ) ) ) {
+  while ( ( comma_ptr = strstr( str, "," ) ) != NULL ) {
     ptr = comma_ptr - 1;
     while ( isspace(*ptr) ) ptr--;
     ptr++; keep = *ptr; *ptr = '\0';
diff --git a/src/xspice/evt/evtdump.c b/src/xspice/evt/evtdump.c
index 15a676277..7c5220b47 100755
--- a/src/xspice/evt/evtdump.c
+++ b/src/xspice/evt/evtdump.c
@@ -292,7 +292,7 @@ void EVTdump(
             if(node_dict[index].send) {
                 /* Scan through new events and send the data for each event */
                 here = *(node_data->last_step[index]);
-                while((here = here->next)) {
+                while((here = here->next) != NULL) {
                     EVTsend_line(node_dict[index].ipc_index,
                                  here->step,
                                  here->node_value,