making a global struct pointer available to multiple source files

Question

I have a struct declared in a header file called h1.h that included in two source files, c1.c and c2.c.

typedef struct
{
    char binary_filename[256];
}programming;

I want to create two variables of this struct, device1 and device2 and then declare two pointers to each of these variables, programmingPtr1 and programmingPtr2.

I want to be able to access the member, binary_filename of a instance in each of the source files.

I'm confused as to where I should declare these variables and pointers.

Should I declare the variables as extern in the header?

I read this post but it doesn't deal with pointers to variables.

Could someone advise please as to the best method?

Answer 1

To use variables in multiple source files, you'll need to declare them in a header file that all relevant sources include, then you define them in exactly one source file.

So your header would have:

extern programming device1;
extern programming device2;
extern programming *programmingPtr1;
extern programming *programmingPtr2;

Then in one source file, you would have:

programming device1 = { "filename1" };
programming device2 = { "filename2" };
programming *programmingPtr1 = &device1;
programming *programmingPtr2 = &device2;