Ensure multi-thread safety.

Author: zoziha

src/stdlib_io_disp.fypp

@@ -8,8 +8,6 @@ submodule (stdlib_io) stdlib_io_disp
     use stdlib_strings, only: to_string
     implicit none
 
-    type(string_type) :: coloum(5)
-
 contains
 
 #!                  | string | data elem 1 | unknown width |  sep  | string | line 1 | defined width |
@@ -47,7 +45,6 @@ contains
         width_  = merge(width_, 80, width_ > 80)
 
         sep_    = optval(sep, "  ")
-        coloum  = string_type(":")
 
         #! Prints header
         if (present(header)) then
@@ -91,7 +88,8 @@ contains
                         write(unit_, "(*(A))") format_output_string(x_str(i, :), width_, brief_, sep_, max_elem_len)
                     end do
 
-                    write(unit_, "(*(A))") format_output_string(coloum(1:merge(size(x, 2), 5, size(x, 2)<=5)), &
+                    write(unit_, "(*(A))") format_output_string( &
+                        string_type(spread(":", 1, merge(size(x, 2), 5, size(x, 2) < 5))), &
                         width_, brief_, sep_, max_elem_len)
                     write(unit_, "(*(A))") format_output_string(x_str(size(x, 1), :), width_, brief_, sep_, max_elem_len)
 
@@ -127,7 +125,8 @@ contains
                         write(unit_, "(*(A))") format_output_string(x(i, :), width_, brief_, sep_, max_elem_len)
                     end do
 
-                    write(unit_, "(*(A))") format_output_string(coloum(1:merge(size(x, 2), 5, size(x, 2)<=5)), &
+                    write(unit_, "(*(A))") format_output_string( &
+                        string_type(spread(":", 1, merge(size(x, 2), 5, size(x, 2) < 5))), &
                         width_, brief_, sep_, max_elem_len)
                     write(unit_, "(*(A))") format_output_string(x(size(x, 1), :), width_, brief_, sep_, max_elem_len)
 
@@ -302,8 +301,7 @@ contains
             write(unit_, "(A)") format_output_string([string_type(header)], width_, brief_, "", len(header))
         end if
 
-        coloum(1) = string_type(x_)
-        write(unit_, "(A)") format_output_string(coloum(1:1), width_, brief_, sep_, len(coloum(1)))
+        write(unit_, "(A)") format_output_string([string_type(x_)], width_, brief_, sep_, len(x_))
 
     end subroutine disp_char