Add suggested changes

Author: Divendra2006

src/fmelt.c

@@ -178,64 +178,60 @@ bool is_default_measure(SEXP vec) {
 // maybe unlist, then unique, then set_diff.
 SEXP uniq_diff(SEXP int_or_list, int ncol, bool is_measure) {
   SEXP int_vec = PROTECT(isNewList(int_or_list) ? unlist_(int_or_list) : int_or_list);
-  
   SEXP is_duplicated = PROTECT(duplicated(int_vec, FALSE)); 
-  
   int n_unique_cols = 0;
-
   SEXP invalid_columns = PROTECT(allocVector(INTSXP, length(int_vec)));
   int* invalid_col_ptr = INTEGER(invalid_columns);
   int invalid_count = 0;
-  
+
   for (int i = 0; i < length(int_vec); ++i) {
     int col_number = INTEGER(int_vec)[i];
-    
     bool good_number = 0 < col_number && col_number <= ncol;
-    
     if (is_measure) good_number |= (col_number == NA_INTEGER);
-    
     if (!good_number || col_number == 0) {
       invalid_col_ptr[invalid_count++] = col_number;
     } else if (!LOGICAL(is_duplicated)[i]) {
       n_unique_cols++;
     }
   }
-  
+
   if (invalid_count > 0) {
-    char buffer[4096] = ""; 
+    int buffer_size = 256;
+    char* error_message = (char*) malloc(buffer_size * sizeof(char));
+    snprintf(error_message, buffer_size, 
+             "One or more values in '%s' are invalid; please fix by removing: ", 
+             is_measure ? "measure.vars" : "id.vars");
     for (int i = 0; i < invalid_count; ++i) {
-      char temp[32];
-      snprintf(temp, 32, "[%d]", invalid_col_ptr[i]); 
-
-      if (i > 0) {
-        strncat(buffer, ", ", sizeof(buffer) - strlen(buffer) - 1); 
+      if (strlen(error_message) + 10 >= buffer_size) {
+        buffer_size *= 2;
+        error_message = (char*) realloc(error_message, buffer_size * sizeof(char));
       }
-      strncat(buffer, temp, sizeof(buffer) - strlen(buffer) - 1); 
-    }
-
-    error(_("One or more values in '%s' are invalid; please fix by removing: %s"), 
-          is_measure ? "measure.vars" : "id.vars", buffer);
+      snprintf(error_message + strlen(error_message), 
+               buffer_size - strlen(error_message), 
+               "[%d]%s", 
+               invalid_col_ptr[i], 
+               (i < invalid_count - 1) ? ", " : "");
+    }
+    error(_("%s"), error_message);
+    free(error_message);
   }
- 
+
   SEXP unique_col_numbers = PROTECT(allocVector(INTSXP, n_unique_cols)); 
   int unique_i = 0;
-  
+
   for (int i = 0; i < length(is_duplicated); ++i) {
     if (!LOGICAL(is_duplicated)[i]) {
       INTEGER(unique_col_numbers)[unique_i++] = INTEGER(int_vec)[i];
     }
   }
-  
+
   SEXP out = set_diff(unique_col_numbers, ncol);
-  
   UNPROTECT(4);
-  
   return out;
 }
 
 
 
-
 SEXP cols_to_int_or_list(SEXP cols, SEXP dtnames, bool is_measure) {
   switch(TYPEOF(cols)) {
   case STRSXP  : return chmatch(cols, dtnames, 0);