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

Sure, you put this in one of your your header files, say preinit.h:

class Init { public: Init() { initialize(); } }; Init init;

and then, in one of your compilation units, put:

void initialize(void) {
    // weave your magic here.
}
#include "preinit.h"

I know that's a kludge but I'm not aware of any portable way to do pre-main initialization without using a class constructor executed at file scope.

You should also be careful of including more than one of these initialization functions since I don't believe C++ dictates the order - it could be random.

I'm not sure of this "sketch" of which you speak but would it be possible to transform the main compilation unit with a script before having it passed to the compiler, something like:

awk '{print;if (substr($0,0,11) == "int main (") {print "initialize();"};}'

You can see how this would affect your program because:

echo '#include 
int main (void) {
    int x = 1;
    return 0;
}' | awk '{
    print;
    if (substr($0,0,11) == "int main (") {
        print "    initialize();"
    }
}'

generates the following with the initialize() call added:

#include 
int main (void) {
    initialize();
    int x = 1;
    return 0;
}

It may be that you can't post-process the generated file in which case you should ignore that final option, but that's what I'd be looking at first.