Modifying APP_ENTRY_POINT

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Richard Hagberg

• June 06, 2018 21:31

I am using a STM32f103CB chip and am creating a bootloader.  In the thumb_crt0.s file, there is a line " #define APP_ENTRY_POINT main" which tells the system which address to branch to on startup. I tried to redefine this for my bootloader, but I always get errors that the function that I am trying to use instead of main (bootmain) is an undefined reference. I have created a bootmain function.Can you actually replace main as the starting function? If so, what are the steps required? I know it is not necessary to rename main to create a bootloader, but I think it helps with clarity. Thanks.

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• 

  Jon Elliott

  • June 07, 2018 15:26
  • Edited

  If your bootmain function is in a C++ file, you'll need to compile it as a C function using extern "C". For example:

  extern "C" int bootmain(int argc, char *argv[])
  {
  }

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  Richard Hagberg

  • June 07, 2018 15:39

  Interesting.  I wouldn't have thought of that because it is being used in a .s file.  Thank you for your reply, I'll give that a try.

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