This is exactly right. Is there a good web page that explains this stuff, so that we don't have to explain these C fundamentals on a regular basis? I know I've had to do it on the avr lists and many other compiler lists, and it gets a bit annoying after a while - especially the invariable arguements with someone who thinks all this "#define EXTERN_GLOBAL extern" shite is a good idea.
If people want to write embedded systems in C, they should first learn to write C. That means learning what "extern" means (as described below), and how headers and source files should be divided up. Just because C is painfully poorly designed language and lets you write disorganised drivel, such as declaring variables in headers, does not mean that this is sensible code to write. mvh., David ----- Original Message ----- From: developer2112 (sent by Nabble.com) To: avr-gcc-list@nongnu.org Sent: Tuesday, January 31, 2006 3:12 AM Subject: Re: [avr-gcc-list] (no subject) Header files aren't meant for declaring variables; it's actually against the ANSI standard. What you need to do is put your global variables in a C file; perhaps globals.c...then create a header file. Title the header file with the same base name, in this case globals.h. Globals.h should look like this: #ifndef _GLOBALS_H_ // i use _BASENAME_H_ use whatever you like #define _GLOBALS_H_ // this prevents multiple includes extern int nMyGlobal; extern ... #endif Then in my C files: #include "globals.h" // this can be used in ALL files, you can even include it in globals.c itself nMyGlobal = 10; If you stick to this convention, you will never have this kind of problem again no matter what ANSI C compiler you are using. Many people don't know it, but you can use extern even if the variable or function is in the same module without any penalties. All it does is it tells the compiler that the reference will be resolved at link time as opposed to compile time. View this message in context: Re: (no subject) Sent from the AVR - gcc forum at Nabble.com. _______________________________________________ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list _______________________________________________ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
