__vectab_stack_and_reset is a library section that provides a way for the initial values of sp and pc to be placed in the vector table, starting at address 0 for M-profile processors, such as Cortex-M1 and Cortex-M3 embedded applications.

__vectab_stack_and_reset requires the existence of a main() function in your source code. Without a main() function, if you place the __vectab_stack_and_reset section in a scatter file, an error is generated to the following effect:

Error: L6236E: No section matches selector - no section to be FIRST/LAST

If the normal start-up code is bypassed, that is, if there is intentionally no main() function, you are responsible for setting up the vector table without __vectab_stack_and_reset.

The following segment is part of a scatter file. It includes a minimal vector table illustrating the use of __vectab_stack_and_reset to place the initial sp and pc values at addresses 0x0 and 0x4 in the vector table:

   ;; Maximum of 256 exceptions (256*4 bytes == 0x400)
   VECTORS 0x0 0x400
   {
       ; First two entries provided by library
       ; Remaining entries provided by the user in exceptions.c

       * (:gdef:__vectab_stack_and_reset, +FIRST)
       * (exceptions_area)
   }

   CODE 0x400 FIXED
   { 
       * (+RO)
   }