initialized and declared 'extern' [enabled by default]

[randenewberry]

We are using Coderwarior 10.5.

We are porting a Coldfire program to a K20 MK20DX128vlh5.

The GCC compiler complains of initialized and declared 'extern' [enabled by default] for all my external variables.

As an example

In the .h file I have

extern const char stCR[2];

In the .c file I have

extern const char stCRLF[]={"\r\n\0"};

This works fine for the Coldfire compiler but the GCC compiler gives a warning for every one of my variables declared as external.

What is the proper syntax to do the same thing in GCC?

Or can this warning be safely ignored?

Thanks

[pgo]

Hi Rande,

You usually associate extern with the declaration of a variable i.e. indicating that it exists somewhere.

You define the variable without the extern.

...but

if you initialise a variable it is always considered a definition irrespective of the extern.

So in summary:

In header file (.h)  where you are declaring the variable use

extern const char stCR[2];

In the actual file (.c file) where you are defining (creating) use

const char stCR[2] = "ab";

This also applies even if not initialising the variable e.g not a constant.

It is only considered a warning but it is best to adopt the suggested approach.

PS.  I presume the inconsistencies in the example in your question are a typo? Otherwise they are different variables.

bye

[mjbcswitzerland]

Hi

You will get complains due to

extern const char stCRLF[]={"\r\n\0"};

when you have

extern const char stCR[2];

since it is "declared" extern but "initialised" extern. GCC warns as default and other compilers may do, depending on the level of warning/error settings.

There is no need to initialise extern when already declared extern so I would remove the extern for all global variables since these 'should' be declared in a header anyway, otherwise they shouldn't be global and so should be static. The warning "could" be ignored since it doesin't cause a problem but people will tend not to trust code with warnings so probably best to drop the externs where initialsiation takes place....

Regards

Mark