Текст программы на языке С, формирующей прямоугольные импульсы на одном из выводов микроконтроллера

$ cat main.c 
#include <stm32f10x.h>
#include "pinmacro.h"
#define F_APB2 72000000
 
void __attribute__((weak)) _init(void){}
void __attribute__((weak)) SystemInit(void){}
 
void sleep(uint32_t x){
  volatile uint32_t i = x;
  while ( i-- );
}
 
void main(void){
  
  while(1){
  }
}
$ make
arm-none-eabi-gcc -mthumb -mcpu=cortex-m3 -fno-builtin -Wall -c  -I. -ggdb -Os -I../Libraries/STM32F10x_StdPeriph_Driver/inc -I../Libraries/CMSIS/CM3/CoreSupport -I../Libraries/CMSIS/CM3/DeviceSupport/ST/STM32F10x -DSTM32F10X_MD_VL   -DVECT_TAB_FLASH -DGCC_ARMCM3   -c -o main.o main.c
main.c:13:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main(void){
      ^~~~
..linking
arm-none-eabi-gcc -T../ld/stm32f100c4.ld -nostartfiles -Wl,-Map -Wl,main.map -mthumb -mcpu=cortex-m3 -o main.out crt.o -L../ld main.o 
# --verbose
arm-none-eabi-size main.out
   text    data     bss     dec     hex filename
    580       0     256     836     344 main.out
...copying
arm-none-eabi-objcopy -Obinary main.out main.bin
arm-none-eabi-objcopy -Oihex main.out main.hex
arm-none-eabi-objdump -D -S main.out > main.list