How can I perform pre-main initialization in C/C++ with avr-gcc?

Question

In order to ensure that some initialization code runs before main (using Arduino/avr-gcc) I have code such as the following:

class Init {
public         


        

Answer 1

Here's a somewhat evil method of achieving this:

#include 

static int bar = 0;

int __real_main(int argc, char **argv);

int __wrap_main(int argc, char **argv)
{
    bar = 1;
    return __real_main(argc, argv);
}

int main(int argc, char **argv)
{
    printf("bar %d\n",bar);
    return 0;
}

Add the following to the linker flags: --wrap main

eg.

gcc -Xlinker --wrap -Xlinker main a.c

The linker will replace all calls to main with calls to __wrap_main, see the ld man page on --wrap