AVR Freaks

I've written a lot about this but, sadly, the search engine here is not very good and it's tricky to find previous responses. However the bottom line is that static libs play NO part in AVR development for EXACTLY the reason you just discovered! Say you have a library for driving an LCD and you want the user to be able to say which PORT pins the LCD is attached to then either you need to do something horrendous like:

enum {
    LCD_PORTA,
    LCD_PORTB,
    LCD_PORTC,
    LCD_PORTD
} lcdPort;

void lcd_init(lcdPort portID) {
    switch (portID) {
        case LCD_PORTA:
            DDRA = 0xFF;
            break;
        case LCD_PORTB:
            DDRB = 0xFF;
            break;
        case LCD_PORTC:
            DDRC = 0xFF;
            break;
        case LCD_PORTD:
            DDRD = 0xFF;
            break;
    }
}

or you have to have the user pass you the addresses of PORTx, DDRx, PINx like:

void lcd_init(volatile uint8_t * lcd_DDR, volatile uint8_t * lcd_PORT, volatile uint8_t * lcd_PIN) {
    *lcd_DDR = 0xFF;
    etc.
}

If, however you give the user a .h and a .c file you can offer:

// lcd.h
#define LCD_DDR DDRB
#define LCD_PORT PORTB
etc.

// lcd.c
void lcd_init() {
    LCD_DDR = 0xFF;
}

Now the user just modifies the given lcd.h, adds the lcd.c to their project and builds it all along with the rest of their code.

The other issue with the liblcd.a solution is that their are 17 different AVR architectures so as a minimum, if you were to offer a prebuilt binary i nthe form of a .a file you would need to supply 17 different variants just as you see here:

avr8-gnu-toolchain-linux_x86_64/avr/lib$ find . -name "lib[c|m].a"
./avr3/libc.a
./avr3/libm.a
./avr4/libc.a
./avr4/libm.a
./avr5/libc.a
./avr5/libm.a
./avrtiny/libc.a
./avrtiny/libm.a
./avrxmega6/libc.a
./avrxmega6/libm.a
./avr31/libc.a
./avr31/libm.a
./avr25/tiny-stack/libc.a
./avr25/tiny-stack/libm.a
./avr25/libc.a
./avr25/libm.a
./avr35/libc.a
./avr35/libm.a
./avr51/libc.a
./avr51/libm.a
./tiny-stack/libc.a
./tiny-stack/libm.a
./avrxmega5/libc.a
./avrxmega5/libm.a
./avrxmega4/libc.a
./avrxmega4/libm.a
./libc.a
./avrxmega2/libc.a
./avrxmega2/libm.a
./libm.a
./avrxmega7/libc.a
./avrxmega7/libm.a
./avr6/libc.a
./avr6/libm.a

That is the library for the avr-gcc C compiler - you can see that it has multiple copies of libm.a and libc.a for this very reason.

So forget about static libs - they have no place for AVR (whatever the confusing project dialog in AS7 might suggest!) and just supply your user with .h/.c (or .cpp) and let them configure and build the code for their intended target.