Unknown type name for struct in header file

Question

I have a header file where I would like to define a few default colors.

typedef struct _color {
    unsigned char r;
    unsigned char g;
    unsigned char b;
    unsigned char a;
} color;

/* Default colors */

// initializes to (0, 0, 0, 0)
color TRANSPARENT;

color color_black;
color_black.a = 255;

color color_red;
color_red.r = 255;
color_red.a = 255;

color GREEN;
GREEN.g = 255;
GREEN.a = 255;

When I compile with clang -I. -c -o image.o image.c, I get the following errors:

In file included from image.c:5:
./image.h:25:1: error: unknown type name 'color_black'
color_black.a = 255;
^
./image.h:25:12: error: expected identifier or '('
color_black.a = 255;
           ^
./image.h:28:1: error: unknown type name 'color_red'
color_red.r = 255;
^
./image.h:28:10: error: expected identifier or '('
color_red.r = 255;
...

This continues for all of the colors I have defined.

I'm not sure why it thinks the variables should be type names, especially when I have already declared them. I have tried using extern and changing the variable names' style to ALL CAPS.

color_black.a = 255; You can't write statement at global scope, all such code must go inside a function. If you just want to initialize the variables, write color color_black = { 0, 0, 0, 255 }; instead. — dxiv
– dxiv, Commented Feb 10, 2021 at 7:16
btw your struct definition is a c-ism. In C++ you can write struct color { ... }; — 463035818_is_not_an_ai
– 463035818_is_not_an_ai, Commented Feb 10, 2021 at 7:18
Defining global variables in header files is not a good idea. — n. m. could be an AI
– n. m. could be an AI, Commented Feb 10, 2021 at 7:18
Please remember that C and C++ are two different languages. Do you need an answer for both? — Bob__
– Bob__, Commented Feb 10, 2021 at 7:21

DownloadPizza · Accepted Answer · 2021-02-10 07:17:34Z

2

You are running code outside of a function.

printf("a");

doesnt compile either, so why should assignment expressions?

instead do

color color_black = {0,0,0,255};

answered Feb 10, 2021 at 7:17

DownloadPizza

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