MSP430F5529: No 'itoa' in library. 'ltoa' does not work correctly

Tool/software:

I have used this code for years with standard library 'itoa' to add an unsigned char value to a string and display it.

Does not work properly using 'ltoa(char str, int val, int radix)'.

I know that some versions of CCS 'ltoa' do not have a radix but that not the problem either.

Note the 'drawText(int x ,int y, unsigned int fg_color, unsigned int bg_color, char const *string)'  function is well proven many times elsewhere in the program.

It prints this:    SLAVE CLOCK #XS

Should print:   SLAVE CLOCK #3

void dispClkID()
{
    unsigned char clk_id;
    char s1[20], s2[3];

/* hardware detection not built yet.
 * clk_id is hard coded until then.
 */
clk_id= 3;

    if (clk_id == 1)  {
        strcpy(s1," MASTER CLOCK #1 ");
        drawText(TEXT_BG_CENTER,textY(0),BLACK,ORANGE,s1);
    }
    else if ((clk_id > 1)&&(clk_id < 5))  {
        ltoa(clk_id,s2,10);
        strcpy(s1,"  SLAVE CLOCK #");
        strcat(s1,s2);
        strcat(s1,"  ");
        drawText(TEXT_BG_CENTER,textY(0),BLACK,ORANGE,s1);
    }
    else  {
        strcpy(s1,"Clock ID not set");
        drawText(TEXT_BG_CENTER,textY(0),RED,BLACK,s1);
    }

}