Start by confirming what's visible to the debugger at 0x08000000 and 0x00000000
Perhaps get STDIO putchar/puts/printf working? So you can output workable diagnosis.
Perhaps view SYSCFG->CFGR1 in the debugger's peripheral register view
The CM0 used in the STM32F0 can't remap the Vector Table via SCB->VTOR
Edit your startup_stm32f030.s
...
.section .text.Reset_Handler
.weak Reset_Handler
.type Reset_Handler, %function
Reset_Handler:
ldr r0, =_estack
mov sp, r0 /* set stack pointer */
/* Call the clock system initialization function.*/
bl SystemInit
/* Check if boot space corresponds to test memory*/
/*SYSCFG clock enable*/
LDR R0,=0x40021018
LDR R1,=0x00000001
STR R1, [R0]
/*Set CFGR1 register with flash memory remap at address 0*/
LDR R0,=0x40010000
LDR R1,=0x00000000
STR R1, [R0]
/* Copy the data segment initializers from flash to SRAM */
ldr r0, =_sdata
ldr r1, =_edata
ldr r2, =_sidata
movs r3, #0
b LoopCopyDataInit
CopyDataInit:
ldr r4, [r2, r3]
str r4, [r0, r3]
adds r3, r3, #4
LoopCopyDataInit:
adds r4, r0, r3
cmp r4, r1
bcc CopyDataInit
/* Zero fill the bss segment. */
ldr r2, =_sbss
ldr r4, =_ebss
movs r3, #0
b LoopFillZerobss
FillZerobss:
str r3, [r2]
adds r2, r2, #4
LoopFillZerobss:
cmp r2, r4
bcc FillZerobss
/* Call static constructors */
bl __libc_init_array
/* Call the application's entry point.*/
bl main
LoopForever:
b LoopForever
.size Reset_Handler, .-Reset_Handler
...
