Thread: Fixing incorrect extern declaration

I'm rephrasing my question on a thread I started earlier since it didn't really help me solve the problem I had.
(The particular thread is:
http://cboard.cprogramming.com/showthread.php?t=88008)

I have an external variable declared in "Globals.h"

Code:

extern float PROB_SMOOTH;

There are tons of other source files that reference this variable but do not declare it IN ANYWAY internally.
For example, a file "NTables.h" has a bunch of code, then in the middle pops out a reference to PROB_SMOOTH without a declaration of PROB_SMOOTH anywhere in "NTables.h".
Also, "Globals.h" does not exist in the header include hierarchy of "NTables.h".

I wish to go about fixing this by declaring

Code:

extern float PROB_SMOOTH;

in all the source files that reference PROB_SMOOTH.

I know it will compile. I've tried it.

But, someone, if I'm doing something wrong here, please let me know.

Thanks. That also solved the problem, so I guess my method would have fouled up the source in some way.

Do you know by any chance of a link that explains why this particular sort of coding will compile in gcc 3.33 but not in gcc 4.0.3?

Yes. It's code I got off the Internet, and in Mac OS 10.3, all you have to do is unzip the thing, run make, and you're ready to use it.

But on Ubuntu, gcc 4.0.3, I've had to
1. use "this->" scope specifiers so that the compiler could find some variables
2. either include a header file where the declaration was made or declare it as extern myself.

For the warnings I got in (1), the warning messages said I could use the flag "-fpermissive" to make it compile, but it discouraged me from doing so. Well, I tried it, didn't work.

With the PROB_SMOOTH variable, it just couldn't find it, only natural considering it was never included. The strange thing is it compiled on OS X.

Anyway, I've "fixed" everything and it's compiling now, so I'm sort of satisfied, but I'd be happier if I new why it compiled on the Mac in the first place.