conditional compilation ?

yes that's it

adresse_mac_ethernet will be defined in all files which include your user.h,

the flag FLAG_ADRESSE_MAC_ETHERNET does not prevent this.

it's better to put the definition of variables in .c files and a extern

declaration for it in the header.

eg

file: user.h

------------------------------------------------------------------------------

// --- choice of board ----------------------------------

# define NIOSII_1

//#define NIOSII_2

extern const char adresse_mac_ethernet[6];

------------------------------------------------------------------------------

file: user.c

------------------------------------------------------------------------------# ifdef NIOSII_1# warning "******************NIOSII_1 defined"

const char adresse_mac_ethernet[6] = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06} ;# endif // NIOSII_1

# ifdef NIOSII_2# warning "************** NIOSII_2 defined"

const char adresse_mac_ethernet[6] = {0x11, 0x12, 0x13, 0x14, 0x15, 0x16} ;# endif // NIOSII_2