why the c compiler doesn't add underscore before symbols.

I am following the UART_hyperterminal_dspL137 example, which defines _intcVectorTable in intvecs.asm and reference it as intcVectorTable in main.c, and define UART2_isr function in main.c and reference it in intvecs.asm as _UART2_isr.

As I know, this is because the c compiler add underscore before symbols automatically. But both the symbols intcVectorTable and _UART2_isr are unlinkable.

I check the map file and found that the compiler doesn't add underscore automatically. I want to know what opition influence this?