diff --git a/src/actions.c b/src/actions.c
index 2dc51239..11974f03 100644
--- a/src/actions.c
+++ b/src/actions.c
@@ -2046,12 +2046,12 @@ void new_polygon(int what) /*  20171115 */
 }
 
 #ifdef HAS_CAIRO
-int text_bbox(char *str, double xscale, double yscale,
+int text_bbox(const char *str, double xscale, double yscale,
     int rot, int flip, int hcenter, int vcenter, double x1,double y1, double *rx1, double *ry1,
     double *rx2, double *ry2)
 {
   int c=0;
-  char *str_ptr;
+  char *str_ptr, *s = NULL;
   double size;
   cairo_text_extents_t ext;
   cairo_font_extents_t fext;
@@ -2069,18 +2069,19 @@ int text_bbox(char *str, double xscale, double yscale,
   ww=0.; hh=1.;
   c=0;
   cairo_lines=1;
-  str_ptr = str;
-  while( str && str[c] ) {
-    if(str[c] == '\n') {
-      str[c]='\0';
+  my_strdup2(1158, &s, str);
+  str_ptr = s;
+  while( s && s[c] ) {
+    if(s[c] == '\n') {
+      s[c]='\0';
       hh++;
       cairo_lines++;
       if(str_ptr[0]!='\0') {
         cairo_text_extents(ctx, str_ptr, &ext);
         if(ext.x_advance > ww) ww= ext.x_advance;
       }
-      str[c]='\n';
-      str_ptr = str+c+1;
+      s[c]='\n';
+      str_ptr = s+c+1;
     } else {
     }
     c++;
@@ -2089,6 +2090,7 @@ int text_bbox(char *str, double xscale, double yscale,
     cairo_text_extents(ctx, str_ptr, &ext);
     if(ext.x_advance > ww) ww= ext.x_advance;
   }
+  my_free(1159, &s);
   hh = hh*fext.height*cairo_font_line_spacing;
   cairo_longest_line = ww;
 
@@ -2125,11 +2127,11 @@ int text_bbox(char *str, double xscale, double yscale,
   RECTORDER((*rx1),(*ry1),(*rx2),(*ry2));
   return 1;
 }
-int text_bbox_nocairo(char * str,double xscale, double yscale,
+int text_bbox_nocairo(const char * str,double xscale, double yscale,
     int rot, int flip, int hcenter, int vcenter, double x1,double y1, double *rx1, double *ry1,
     double *rx2, double *ry2)
 #else
-int text_bbox(char * str,double xscale, double yscale,
+int text_bbox(const char * str,double xscale, double yscale,
     int rot, int flip, int hcenter, int vcenter, double x1,double y1, double *rx1, double *ry1,
     double *rx2, double *ry2)
 #endif
diff --git a/src/draw.c b/src/draw.c
index af394e6a..dd310bca 100644
--- a/src/draw.c
+++ b/src/draw.c
@@ -288,10 +288,10 @@ void cairo_draw_string_line(cairo_t *ctx, char *s,
 }
 
 /* CAIRO version */
-void draw_string(int layer, int what, char *s, int rot, int flip, int hcenter, int vcenter,
+void draw_string(int layer, int what, const char *s, int rot, int flip, int hcenter, int vcenter,
                  double x, double y, double xscale, double yscale)
 {
-  char *tt, *ss;
+  char *tt, *ss, *sss=NULL;
   char c;
   int lineno=0; 
   double size;
@@ -343,9 +343,9 @@ void draw_string(int layer, int what, char *s, int rot, int flip, int hcenter, i
   cairo_set_font_size (ctx, size*mooz);
   cairo_set_font_size (save_ctx, size*mooz);
   cairo_font_extents(ctx, &fext);
-  /*fprintf(errfp, "cairo_draw_string(): s=%s lines=%d\n", s, cairo_lines); */
   llength=0;
-  tt=ss=s;
+  my_strdup2(73, &sss, s);
+  tt=ss=sss;
   for(;;) {
     c=*ss;
     if(c=='\n' || c==0) {
@@ -365,12 +365,13 @@ void draw_string(int layer, int what, char *s, int rot, int flip, int hcenter, i
     }
     ss++;
   }
+  my_free(1157, &sss);
 }
 
 #else /* !HAS_CAIRO */
 
 /* no CAIRO version */
-void draw_string(int layer, int what, char *str, int rot, int flip, int hcenter, int vcenter, 
+void draw_string(int layer, int what, const char *str, int rot, int flip, int hcenter, int vcenter, 
                  double x1,double y1, double xscale, double yscale)  
 {
  double a=0.0,yy;
@@ -431,7 +432,7 @@ void draw_string(int layer, int what, char *str, int rot, int flip, int hcenter,
 
 #endif /* HAS_CAIRO */
 
-void draw_temp_string(GC gctext, int what, char *str, int rot, int flip, int hcenter, int vcenter,
+void draw_temp_string(GC gctext, int what, const char *str, int rot, int flip, int hcenter, int vcenter,
                  double x1,double y1, double xscale, double yscale)  
 {
  if(!has_x) return;
@@ -545,11 +546,12 @@ void draw_symbol(int what,int c, int n,int layer,int tmp_flip, int rot,
   }
   if( (layer==TEXTWIRELAYER && !(inst_ptr[n].flags&2) ) || 
       (sym_txt && (layer==TEXTLAYER) && (inst_ptr[n].flags&2) ) ) {
+    const char *txtptr;
     for(j=0;j< symptr->texts;j++)
     {
       text = symptr->txtptr[j];
       if(text.xscale*FONTWIDTH*mooz<1) continue;
-      text.txt_ptr= translate(n, text.txt_ptr);
+      txtptr= translate(n, text.txt_ptr);
       ROTATION(0.0,0.0,text.x0,text.y0,x1,y1);
 
       textlayer = c;
@@ -567,7 +569,8 @@ void draw_symbol(int what,int c, int n,int layer,int tmp_flip, int rot,
           cairo_select_font_face (save_ctx, textfont, CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL);
         }
         #endif
-        draw_string(textlayer, what, text.txt_ptr,
+        dbg(1, "drawing string: str=%s prop=%s\n", txtptr, text.prop_ptr);
+        draw_string(textlayer, what, txtptr,
           (text.rot + ( (flip && (text.rot & 1) ) ? rot+2 : rot) ) & 0x3,
           flip^text.flip, text.hcenter, text.vcenter, 
           x0+x1, y0+y1, text.xscale, text.yscale);                    
@@ -686,17 +689,17 @@ void draw_temp_symbol(int what, GC gc, int n,int layer,int tmp_flip, int rot,
 
  if(layer==PROPERTYLAYER && sym_txt)
  {
+  const char *txtptr;
   for(j=0;j< symptr->texts;j++)
   {
    text = symptr->txtptr[j];
    if(text.xscale*FONTWIDTH*mooz<1) continue;
-   text.txt_ptr= 
-     translate(n, text.txt_ptr);
+   txtptr= translate(n, text.txt_ptr);
    ROTATION(0.0,0.0,text.x0,text.y0,x1,y1);
    #ifdef HAS_CAIRO
    customfont = set_text_custom_font(&text);
    #endif
-   if(text.txt_ptr[0]) draw_temp_string(gc, what, text.txt_ptr,
+   if(txtptr[0]) draw_temp_string(gc, what, txtptr,
      (text.rot + ( (flip && (text.rot & 1) ) ? rot+2 : rot) ) & 0x3,
      flip^text.flip, text.hcenter, text.vcenter, x0+x1, y0+y1, text.xscale, text.yscale);                    
    #ifdef HAS_CAIRO
diff --git a/src/psprint.c b/src/psprint.c
index 1524b558..cdf1352a 100644
--- a/src/psprint.c
+++ b/src/psprint.c
@@ -164,7 +164,7 @@ static void ps_drawline(int gc, double linex1,double liney1,double linex2,double
   }
 }
 
-static void ps_draw_string(int gctext,  char *str, 
+static void ps_draw_string(int gctext,  const char *str, 
                  int rot, int flip, int hcenter, int vcenter, 
                  double x1,double y1,
                  double xscale, double yscale)  
@@ -340,12 +340,12 @@ static void ps_draw_symbol(int n,int layer,int tmp_flip, int rot,
    if(  (layer==TEXTWIRELAYER  && !(inst_ptr[n].flags&2) ) || 
         (sym_txt && (layer==TEXTLAYER)   && (inst_ptr[n].flags&2) ) )
    {
+    const char *txtptr;
     for(j=0;j< (inst_ptr[n].ptr+instdef)->texts;j++)
     {
      text = (inst_ptr[n].ptr+instdef)->txtptr[j];
      /* if(text.xscale*FONTWIDTH* mooz<1) continue; */
-     text.txt_ptr= 
-       translate(n, text.txt_ptr);
+     txtptr= translate(n, text.txt_ptr);
      ROTATION(0.0,0.0,text.x0,text.y0,x1,y1);
      textlayer = layer;
      if( !(layer == PINLAYER && (inst_ptr[n].flags & 4))) {
@@ -353,7 +353,7 @@ static void ps_draw_symbol(int n,int layer,int tmp_flip, int rot,
        if(textlayer < 0 || textlayer >= cadlayers) textlayer = layer;
      }
      if((layer == PINLAYER && inst_ptr[n].flags & 4) ||  enable_layer[textlayer]) {
-       ps_draw_string(textlayer, text.txt_ptr,
+       ps_draw_string(textlayer, txtptr,
          (text.rot + ( (flip && (text.rot & 1) ) ? rot+2 : rot) ) & 0x3,
          flip^text.flip, text.hcenter, text.vcenter,
          x0+x1, y0+y1, text.xscale, text.yscale);                    
diff --git a/src/save.c b/src/save.c
index 44af29af..27d05fe2 100644
--- a/src/save.c
+++ b/src/save.c
@@ -1479,7 +1479,7 @@ int load_sym_def(const char *name, FILE *embed_fd)
      fscanf(lcc[level].fd, "%lf %lf %d %d %lf %lf ",&tt[i].x0, &tt[i].y0, &tt[i].rot,
         &tt[i].flip, &tt[i].xscale, &tt[i].yscale);
      if (level>0) {
-       char* tmp = translate2(lcc, level, tt[i].txt_ptr);
+       const char* tmp = translate2(lcc, level, tt[i].txt_ptr);
        if (tmp) my_strdup(651, &tt[i].txt_ptr, tmp);
        ROTATION(0.0, 0.0, tt[i].x0, tt[i].y0, rx1, ry1);
        tt[i].x0 = lcc[level].x0 + rx1;  tt[i].y0 = lcc[level].y0 + ry1;
@@ -1488,7 +1488,7 @@ int load_sym_def(const char *name, FILE *embed_fd)
      }
      tt[i].prop_ptr=NULL;
      load_ascii_string(&tt[i].prop_ptr, lcc[level].fd);
-      dbg(2, "l_d_s(): loaded text\n");
+     dbg(1, "l_d_s(): loaded text : t=%s p=%s\n", tt[i].txt_ptr, tt[i].prop_ptr);
 
      my_strdup(351, &tt[i].font, get_tok_value(tt[i].prop_ptr, "font", 0));/*20171206 */
 
diff --git a/src/select.c b/src/select.c
index fe5850a2..bcb056d4 100644
--- a/src/select.c
+++ b/src/select.c
@@ -32,7 +32,7 @@ void symbol_bbox(int i, double *x1,double *y1, double *x2, double *y2)
 {
    int j;
    Text text;
-   char *tmp_txt;
+   const char *tmp_txt;
    int rot,flip;
    double x0, y0 ;
    double text_x0, text_y0;
diff --git a/src/svgdraw.c b/src/svgdraw.c
index 200c64e4..ea586f88 100644
--- a/src/svgdraw.c
+++ b/src/svgdraw.c
@@ -192,7 +192,7 @@ static void svg_drawline(int gc, double linex1,double liney1,double linex2,doubl
   }
 }
 
-static void svg_draw_string(int gctext,  char *str, 
+static void svg_draw_string(int gctext, const char *str, 
                  int rot, int flip, int hcenter, int vcenter, 
                  double x1,double y1,
                  double xscale, double yscale)  
@@ -367,12 +367,12 @@ static void svg_draw_symbol(int n,int layer,int tmp_flip, int rot,
    if(  (layer==TEXTWIRELAYER  && !(inst_ptr[n].flags&2) ) || 
         (sym_txt && (layer==TEXTLAYER)   && (inst_ptr[n].flags&2) ) )
    {
+    const char *txtptr;
     for(j=0;j< (inst_ptr[n].ptr+instdef)->texts;j++)
     {
      text = (inst_ptr[n].ptr+instdef)->txtptr[j];
      /* if(text.xscale*FONTWIDTH* mooz<1) continue; */
-     text.txt_ptr= 
-       translate(n, text.txt_ptr);
+     txtptr= translate(n, text.txt_ptr);
      ROTATION(0.0,0.0,text.x0,text.y0,x1,y1);
      textlayer = layer;
      if( !(layer == PINLAYER && (inst_ptr[n].flags & 4))) {
@@ -380,7 +380,7 @@ static void svg_draw_symbol(int n,int layer,int tmp_flip, int rot,
        if(textlayer < 0 || textlayer >= cadlayers) textlayer = layer;
      }
      if((layer == PINLAYER && inst_ptr[n].flags & 4) ||  enable_layer[textlayer]) {
-       svg_draw_string(textlayer, text.txt_ptr,
+       svg_draw_string(textlayer, txtptr,
          (text.rot + ( (flip && (text.rot & 1) ) ? rot+2 : rot) ) & 0x3,
          flip^text.flip, text.hcenter, text.vcenter, 
          x0+x1, y0+y1, text.xscale, text.yscale);                    
diff --git a/src/token.c b/src/token.c
index 1d6a784a..26db2e2a 100644
--- a/src/token.c
+++ b/src/token.c
@@ -757,7 +757,7 @@ void new_prop_string(int i, const char *old_prop, int fast, int disable_unique_n
  my_free(988, &new_name);
 }
 
-char *subst_token(const char *s, const char *tok, const char *new_val)
+const char *subst_token(const char *s, const char *tok, const char *new_val)
 /* given a string <s> with multiple "token=value ..." assignments */
 /* substitute <tok>'s value with <new_val> */
 /* if tok not found in s and new_val!=NULL add tok=new_val at end.*/
@@ -2454,8 +2454,9 @@ const char *find_nth(const char *str, char sep, int n)
 /* substitute given tokens in a string with their corresponding values */
 /* ex.: name=@name w=@w l=@l ---> name=m112 w=3e-6 l=0.8e-6 */
 /* if s==NULL return emty string */
-char *translate(int inst, char* s)
+const char *translate(int inst, char* s)
 {
+ static char empty[]="";
  static char *result=NULL;
  int size=0, tmp;
  register int c, state=XBEGIN, space;
@@ -2474,7 +2475,7 @@ char *translate(int inst, char* s)
 
  if(!s) {
    my_free(1063, &result);
-   return "";
+   return empty;
  }
     
  size=CADCHUNKALLOC;
@@ -2748,8 +2749,9 @@ char *translate(int inst, char* s)
  return result;
 }
 
-char* translate2(struct Lcc *lcc, int level, char* s)
+const char *translate2(struct Lcc *lcc, int level, char* s)
 {
+  static char empty[]="";
   static char *result = NULL;
   int i, size = 0, tmp, save_tok_size, save_value_size;
   register int c, state = XBEGIN, space;
@@ -2764,7 +2766,7 @@ char* translate2(struct Lcc *lcc, int level, char* s)
 
   if(!s) {
     my_free(1068, &result);
-    return "";
+    return empty;
   }
   size = CADCHUNKALLOC;
   my_realloc(661, &result, size);
diff --git a/src/xschem.h b/src/xschem.h
index 8a488b3c..a2d448db 100644
--- a/src/xschem.h
+++ b/src/xschem.h
@@ -717,7 +717,7 @@ extern void polygon_bbox(double *x, double *y, int points, double *bx1, double *
 extern void arc_bbox(double x, double y, double r, double a, double b, double *bx1, double *by1, double *bx2, double *by2);
 extern void bbox(int what,double x1,double y1, double x2, double y2);
 extern int set_text_custom_font(Text *txt);
-extern int text_bbox(char * str,double xscale, double yscale,
+extern int text_bbox(const char * str,double xscale, double yscale,
             int rot, int flip, int hcenter, int vcenter, double x1,double y1, double *rx1, double *ry1,
             double *rx2, double *ry2);
 
@@ -733,7 +733,7 @@ extern struct int_hashentry *int_hash_lookup(struct int_hashentry **table, int t
 extern void free_int_hash(struct int_hashentry **table); /*  20180104 */
 
 #ifdef HAS_CAIRO
-extern int text_bbox_nocairo(char * str,double xscale, double yscale,
+extern int text_bbox_nocairo(const char * str,double xscale, double yscale,
             int rot, int flip, int hcenter, int vcenter, double x1,double y1, double *rx1, double *ry1,
             double *rx2, double *ry2);
 #endif
@@ -759,7 +759,7 @@ extern Selected find_closest_obj(double mx,double my);
 extern void find_closest_net_or_symbol_pin(double mx,double my, double *x, double *y);
 
 extern void drawline(int c, int what, double x1,double y1,double x2,double y2);
-extern void draw_string(int layer,int what, char *str, int rot, int flip, int hcenter, int vcenter, 
+extern void draw_string(int layer,int what, const char *str, int rot, int flip, int hcenter, int vcenter, 
        double x1, double y1, double xscale, double yscale);
 extern void draw_symbol(int what,int c, int n,int layer,
             int tmp_flip, int tmp_rot, double xoffset, double yoffset);
@@ -780,7 +780,7 @@ extern void drawtemppolygon(GC gc, int what, double *x, double *y, int points);
 extern void drawpolygon(int c, int what, double *x, double *y, int points, int poly_fill);
 extern void draw_temp_symbol(int what, GC gc, int n,int layer,
             int tmp_flip, int tmp_rot, double xoffset, double yoffset);
-extern void draw_temp_string(GC gc,int what, char *str, int rot, int flip, int hcenter, int vcenter, 
+extern void draw_temp_string(GC gc,int what, const char *str, int rot, int flip, int hcenter, int vcenter, 
        double x1, double y1, double xscale, double yscale);
 
 
@@ -891,8 +891,8 @@ extern struct hashentry *hash_lookup(struct hashentry **table, const char *token
 
 extern const char *find_nth(const char *str, char sep, int n);
 extern int isonlydigit(const char *s);
-extern char *translate(int inst, char* s);
-extern char* translate2(struct Lcc *lcc, int level, char* s);
+extern const char *translate(int inst, char* s);
+extern const char* translate2(struct Lcc *lcc, int level, char* s);
 extern void print_tedax_element(FILE *fd, int inst);
 extern void print_spice_element(FILE *fd, int inst);
 extern void print_spice_subckt(FILE *fd, int symbol);
@@ -915,7 +915,7 @@ extern void my_realloc(int id, void *ptr,size_t size);
 extern void *my_calloc(int id, size_t nmemb, size_t size);
 extern void my_free(int id, void *ptr);
 extern size_t my_strcat(int id, char **, const char *);
-extern char *subst_token(const char *s, const char *tok, const char *new_val);
+extern const char *subst_token(const char *s, const char *tok, const char *new_val);
 extern void new_prop_string(int i, const char *old_prop,int fast, int disable_unique_names);
 extern void hash_name(char *token, int remove);
 extern void hash_all_names(int n);