Interrupt vector issues ( cant figure it out!)

Hello, I am having issues implementing the ISR routine on the CORTEX-M3, this exact setup works when I use it with RTX but not as standalone code. When I compile it says cancpp.axf: Error: L6218E: Undefined symbol GPI_ISR (referred from startup.o). But no issues when I build with RTX OS selected.

This is a snip-it of code: GPI_ISR should be the function it branches to.

******************************************************************************
;
; The vector table.
;
;******************************************************************************
        EXPORT  __Vectors
                IMPORT  GPI_ISR ;[WEAK]



__Vectors
        DCD     StackMem + Stack            ; Top of Stack
        DCD     Reset_Handler               ; Reset Handler
        DCD     NmiSR                       ; NMI Handler
        DCD     FaultISR                    ; Hard Fault Handler
        DCD     IntDefaultHandler           ; MPU Fault Handler
        DCD     IntDefaultHandler           ; Bus Fault Handler
        DCD     IntDefaultHandler           ; Usage Fault Handler
        DCD     0                           ; Reserved
        DCD     0                           ; Reserved
        DCD     0                           ; Reserved
        DCD     0                           ; Reserved
        DCD     IntDefaultHandler           ; SVCall handler
        DCD     IntDefaultHandler           ; Debug monitor handler
        DCD     0                           ; Reserved
        DCD     IntDefaultHandler           ; PendSV Handler
        DCD     IntDefaultHandler           ; SysTick Handler
        DCD     GPI_ISR                             ; GPIO Port A

.

in the main.c I have

void   GPI_ISR   (void)
{

}

.