debugging - C Why Variable is unused? -

i need debugging program, how come program tells me have unused variable, have defined table mst[num_pt] right after create structure. ive tried moving around , defining in other places assigning mst[0] @ other places no luck. have syntax error? snippet of code referring near end thought might have entire program.

#include <stdio.h> #include <string.h> #include <stdlib.h> #include <time.h> int main(int argc, char *argv[]) {   file *fp;   int max_x, max_y, num_pt;   int *x_coordinate, *y_coordinate;   int inputfile = 0, outputfile = 0;   int i;   int count,dist,spot;   char black[24],white[24];    typedef struct{     char colour[24];     int x;     int y;     int pos;   }table;    strcpy(black,"black");   strcpy(white,"white");   if (argc == 1) {     /* generate random instances, accepting parameters stdin */     return 1;   }   (i = 1; < argc; i++) {     if (strcmp (argv[i], "-i") == 0)       inputfile = i+1;     else if (strcmp (argv[i], "-o") == 0)       outputfile = i+1;   }   if (inputfile == 0) {     printf("error file not exit!\n");     return -1;   }   if ((fp = fopen(argv[inputfile], "r")) == null) {     printf("error name of file not exist!\n");     return -2;   }   while (fscanf(fp, "%d", &max_x) != 1) {     if (ferror(fp)) {       /* read error */       printf("error max value not equal 1!\n");       fclose(fp);       return -3;     }     if (feof(fp)) {       /* no integer read */       printf("error no numbers read in file!\n");       fclose(fp);       return -4;     }     fscanf(fp, "%*[^\n]"); /* skip rest of line */   }   if (fscanf(fp, "%d", &max_y) != 1) {     /* max_y not following max_x */     printf("error format x not follwing y\n");     fclose(fp);     return -5;   }   while (fscanf(fp, "%d", &num_pt) != 1) {     if (ferror(fp)) {       /* read error */       printf("error num_pt != 1\n");       fclose(fp);       return -6;     }     if (feof(fp)) {       /* no integer read */       printf("error file empty!\n");       fclose(fp);       return -7;     }     fscanf(fp, "%*[^\n]"); /* skip rest of line */   }   x_coordinate = (int *)malloc(num_pt * sizeof(int));   y_coordinate = (int *)malloc(num_pt * sizeof(int));   (i = 0; < num_pt; i++) {     while (fscanf(fp, "%d", &x_coordinate[i]) != 1) {       if (ferror(fp)) {     printf("coordinate reading error!\n");     /* read error */     fclose(fp);        return -8;       }       if (feof(fp)) {     /* no integer read */     printf("error no integers read\n");     fclose(fp);     return -9;       }       fscanf(fp, "%*[^\n]"); /* skip rest of line */    }     if (fscanf(fp, "%d", &y_coordinate[i]) != 1) {       /* y_coordinate not following x_coordinate */       printf("error x/y not following each other\n");       fclose(fp);       return -10;     }   }   fclose(fp);    for(count=0;count<num_pt;count++){     strcpy(nodes[count].colour,white);     nodes[count].pos = count;     nodes[count].x = x_coordinate[count];     nodes[count].y = y_coordinate[count];   }   table nodes[num_pt],parent[1],small[num_pt],mst[num_pt];   mst[0] = nodes[0];   strcpy(nodes[0].colour,black);   parent[0] = nodes[0];   for(spot=1;spot<num_pt;spot++){     for(count=0;count<num_pt;count++){       dist = (nodes[count].x-parent[0].x)+(nodes[count].y-parent[0].y);       if (dist > 0 && strcmp(nodes[count].colour,white) == 0){     small[0] = nodes[count];       }     }     printf("found node %d --> nodes %d closest\n",parent[0].pos,small[0].pos);     parent[0] = small[0];     mst[spot] = small[0];     strcpy(nodes[small[0].pos].colour,black);   }   //int labelx=0,labely=0;    /*     if (outputfile > 0) {     if ((fp = fopen(argv[outputfile], "w")) == null) {     printf("error, can't open print file\n");     return -2;       }     fprintf(fp, "##################################################\n");     fprintf(fp, "#%s\n", argv[inputfile]);     fprintf(fp, "#area [0, max_x] x [0, max_y]\n");     fprintf(fp, "%d\t%d\n", max_x, max_y);     fprintf(fp, "#number of points num_pt\n");     fprintf(fp, "%d\n", num_pt);     fprintf(fp, "#coordinates\n");     (i = 0; < num_pt; i++) {       fprintf(fp, "%d\t%d\n", x_coordinate[i], y_coordinate[i]);     }     fprintf(fp, "#end of instance\n");     fprintf(fp, "#edges of mst prim's algorithm:\n");      fclose(fp);  }   */      printf("choosing point 0 root ...\n");   (i = 1; < num_pt; i++) {     printf("point %d has distance %d tree, parent 0;\n", i,(abs(x_coordinate[0] - x_coordinate[i])) + (abs(y_coordinate[0] - y_coordinate[i])));   }   printf("#edges of mst prim's algorithm\n");   /*   for(count=0;count<num_pt;count++){     totalmst=totalmst+mst[count].dist;     printf("%d %d %d\n",mst[count].coord[1],mst[count].coord[0],mst[count].dist);   }   printf("the total length of mst %d.\n",totalmst);   */   free(x_coordinate);   free(y_coordinate);   return 0; } 

the console returns:

ass2.c: in function ‘main’: ass2.c:105:12: error: ‘nodes’ undeclared (first use in function)      strcpy(nodes[count].colour,white);             ^ ass2.c:105:12: note: each undeclared identifier reported once each function appears in ass2.c:110:47: warning: variable ‘mst’ set not used [-wunused-but-set-variable]    table nodes[num_pt],parent[1],small[num_pt],mst[num_pt]; 

don't worry mst issue. take care of nodes issue , worry subsequent errors. chances mst issue disappear.

also, cannot declare arrays runtime-determined sizes way. expect if increased warnings (-wall gcc) might more clarity on how seeing came be.

do this: table* nodes,small,mst; table parent[1];

nodes = malloc(sizeof(/* "whatever things in array" */) * num_pt); /*  * likewise other `table` arrays.  */ 

also, seem using 2 different vars named nodes! check loop right above table array declarations. ain't right here.