extern and enum typed variables

[Charlie]

I use a file to define all of my global variables, data.c, and then I
create a header file, data.h, where I reference all the variables with
the keyword "extern." I include the header in every file.

I define an enum and variable of that type in data.c,

enum myenum
{
val1,
val2,
val3
} enum_var;

When I try to reference the variable, enum_var, in data.h the compiler
does not like it.

I have tried multiple ways of referencing it but I fail each time so
there is clearly something I do not understand about enum or extern or
god knows what.

So I guess to sum up my question is how do I reference the variable
enum_var so that I can include it in each file.

All help would be appreciated.

Thank You,

Charlie

 

[Chris Dollin]

I use a file to define all of my global variables, data.c, and then I
create a header file, data.h, where I reference all the variables with
the keyword "extern." I include the header in every file.

Good stuff. (You're not /referencing/ the variables; you're /declaring/
them, saying that they exist.)

Note: /don't use global variables unless you have to/. They're an
easy way to get your kickers in a twinge. You know the way egg-white
is nice and fluid before cooking, but cooking it -- cross-connecting
all those protein strands -- makes it, if not actually /hard/, much
stiffer and not a fluid? Global variables are like that, they make
it harder (and harder and harder) to rearrange your program as time
goes by and each variable cross-connects to more and more bits of
code until your trapped in a maze of twisty little codelines all
almost, but not quite, completely different.

I define an enum and variable of that type in data.c,

enum myenum
{
val1,
val2,
val3
} enum_var;

That enum isn't visible in `data.h` and so not to anything that includes
it.

When I try to reference the variable, enum_var, in data.h the compiler
does not like it.

Good compiler, here's a biscuit.

I have tried multiple ways of referencing it but I fail each time so
there is clearly something I do not understand about enum or extern or
god knows what.

So I guess to sum up my question is how do I reference the variable
enum_var so that I can include it in each file.

All help would be appreciated.

Put the declaration in the header file, same as you do for all the
other variables.

 

[pete]

I use a file to define all of my global variables, data.c, and then I
create a header file, data.h, where I reference all the variables with
the keyword "extern." I include the header in every file.

I define an enum and variable of that type in data.c,

enum myenum
{
val1,
val2,
val3
} enum_var;

When I try to reference the variable, enum_var, in data.h the compiler
does not like it.

I have tried multiple ways of referencing it but I fail each time so
there is clearly something I do not understand about enum or extern or
god knows what.

So I guess to sum up my question is how do I reference the variable
enum_var so that I can include it in each file.

All help would be appreciated.

It's OK to define typedefs and enum types in a header file.
Not OK for objects and functions

This would be OK in a header file:
enum myenum {
val1,
val2,
val3
};