Exchange variables between files in C

Question

I have two files:

hudwidgets.c

#include "osd.h"
#include "osdadd.h"
#include <stdio.h>

struct TextSize tsize;
char buff[50];

void hud_draw_lin_compass(int cx, int cy, int tick_maj, int tick_min, int range, int heading)
{
    .. important code that uses buff ..
}

hud.c

#include "hudwidgets.h"
#include "hud.h"
#include "osd.h"
#include "osdadd.h"

.. some code ..

void hud_rc_plane_single_frame()
{
    fill_mem(0x0000);
    if((frame / 50) % 2 == 0)
    {
        get_next_warning(buff);
    }
    .. some more code ..
}

The problem is that when I try to compile this, the compiler complains about no buff, but when I try to define it, the linker complains about two variables buff. Catch 22. For this, I ask two questions:

• How to fix it;

• if you can use the same variable, saving memory, because you need to allocate only one variable (work with a microcontroller with a limited amount of memory.)

Answer 1

You need this at the top of hud.c and any other .c file from which you use them:

extern struct TextSize tsize;
extern char buff[50];

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, , .h, "extern" , .

Answer 2

"extern char buff [50];" , . , , .