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'code U8 u8data' visible in all sources files ?

Hi all,

I've a file named FONT.H where are located some text fonts in code.
They are defined and initialized like this:

code U8 au8FontSystem5x8[]= {
0x00,0x00,0x00,0x00,0x00, /* Espace	0x20 */
0x00,0x00,0x4f,0x00,0x00, /* ! */
...
...
}

My graphic routines are located in a GLCD.C file.
In the GLCD.H, I've defined and declared structures like this :

typedef struct FONT_DEF
{
	U8 u8Width;     	/* Character width for storage         */
	U8 u8Height;  		/* Character height for storage        */
	U8 *au8FontTable;       /* Font table start address in memory  */
} FONT_DEF;

struct FONT_DEF *pptr;

extern struct FONT_DEF code Font_System5x8 = {5, 8, au8FontSystem5x8};
extern struct FONT_DEF code Font_System7x8 = {7, 8, au8FontSystem7x8};

Using these structures in the GLCD.C file is working fine.

However, an other module which includes the GLCD.H file, should call a Graphic function located in the GLCD.C file which display text and pass the pointer to a font structure as parameter :

GLCD_Printf("Hello world", &FontSystem5x8);

But, an error message occurs when including GLCD.H :

***ÿERROR 202 IN LINE 35 OF GLCD.H: 'au8FontSystem5x8': undefined identifier

This means that the code defined in FONT.H isn't available for other modules than GLCD.C where it's included.

The problem is that I can't include FONT.H in all the modules because of multiple definition and code size.
But how to make this code visible everywhere.

I've tried :

extern code U8 au8FontSystem5x8[]= {
0x00,0x00,0x00,0x00,0x00, /* Espace	0x20 */
0x00,0x00,0x4f,0x00,0x00, /* ! */
...
...
}

without success

Any suggestion ?

Regards
Stephane

Parents

0 REY Stephane over 22 years ago in reply to erik malund

I understand that you use a condition to put or not the 'extern' command.
When including the *.h file from an other module, the datas in code are then declared as extern.

But when always setting to 'extern', the datas in code are not seen in my other module.

I don't understand why it isn't, and I don't understand how your code above will solve it... What have I missed ?

Stephane
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0 REY Stephane over 22 years ago in reply to erik malund

I understand that you use a condition to put or not the 'extern' command.
When including the *.h file from an other module, the datas in code are then declared as extern.

But when always setting to 'extern', the datas in code are not seen in my other module.

I don't understand why it isn't, and I don't understand how your code above will solve it... What have I missed ?

Stephane
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0 HansBernhard Broeker over 22 years ago in reply to REY Stephane
... Please no that this has absolutely no relevance to Keil tools --- you're asking very basic questions about C, which you should have learned from your textbook of choice, or ask about elsewhere.

The key is that you have "extern" declarations (_not_ definitions) in the .h file, and actual definitions (usually without "extern") in exactly one of the .C files. e.g.

foo.h:
extern int variable;

foo.c:
#include "foo.h" /*...*/ int variable = 5;
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0 erik malund over 22 years ago in reply to REY Stephane
Extracting from my previous post

#if MAIN code u8 text_string[]{hello again}; #else extern code U8 text_string; #endif
will make the string stored in "main" and be referenced as an extern in other modules.

Erik
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0 REY Stephane over 22 years ago in reply to erik malund

Thanks for all these informations.

I won't post any message which doesn't concern Keil tools.

I'm sorry.

Stephane REY
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0 Dan Henry over 22 years ago in reply to REY Stephane

Hey, no need to apologize -- your code uses the Keil keyword code, so you see, it was relevant to Keil tools after all. But really, where to place defs vs. decls is a pretty general 'C' thing.
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0 HansBernhard Broeker over 22 years ago in reply to erik malund
Well, if you really want to pursue that old trick... here's how you can do even better than that:

In the header file for 'main.c', you would have this after all #includes of other files, but before any of the variables and functions:

#ifdef WE_ARE_COMPILING_MAIN_C # define DEFINE_INITIALIZED(type, name, ini) type name = ini #else # define DEFINE_INITIALIZED(type, name, ini) extern type name #endif

Then you can replace all your individual #ifdef's by calls to this macro:

DEFINE_INITIALIZED(code u8, textstring[], "hello, again");

OTOH, my personal preference is to avoid having initializers in the header file. This means you have to maintain the extern declaration and the actual definition in separate files, but the clarity is worth that.
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0 Jon Ward over 22 years ago in reply to HansBernhard Broeker

Take a look at the following knowledgebase article that addresses that very topic:

http://www.keil.com/support/docs/1868.htm

Jon
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