CODEWITHSUNDEEP
c
Jin
Jin

Reputation: 113

Handling variables defined in c file not header file

My unknown predecessor who has gone left codes. I try to use some of them, but his codes look unusual.

1.What he did is define variables in not a header but c file : variables.c

CHGR_CMD comand[MAX_COMANDS] __attribute__ ((section ("external"))); 
RAWDAT rawdat[MAX_RAWDAT] __attribute__ ((section ("external")));     
SC_TEST *curr_test[NUMCHANS];   /* array of pointers to current testrec */
SC_TESTSETUP chparam[NUMCHANS] __attribute__ ((section ("external")));  
SC_HOLDSTAT  stats[NUMCHANS] __attribute__ ((section ("external")));   
RAWDAT  *bufs[NUMCHANS]; 
//FACTS  control[NUMCHANS];  

short ntest;    
short new_dbuff;    
short start_err;    
short update_status;
long  status_sent;  
short load_done;    
char h_lok;   ....

2 init_vars() in another c file initializes above variables : init_vars.c

memset((char *) rawdat,0 ,sizeof(rawdat));
memset((char *) curr_test,0 ,sizeof(curr_test));
memset((char *) chparam,0 ,sizeof(chparam));
memset((char *) stats,0 ,sizeof(stats));
memset((char *) bufs,0 ,sizeof(bufs));

memset((char *) comand,0 ,sizeof(comand));
ntest = 0;
new_dbuff = 0;

start_err = 0;

3.call init_vars() in main.c

The first time I tried to include "variables.c" directly in init_vars.c, but it gave me below errors:

#10056 symbol "ad_lok" redefined: first defined in "./variables.obj"; redefined in "./init_vars.obj"    sCharger_Test_v1            C/C++ Problem

Not only ad_lok variable but also every variables defined in variables.c hit errors.

Changing variables.c to variables.h still gives me same errors.

How can I handles variables defined c file not header file?

Thanks

Upvotes: 1

Views: 885

Answers (1)

Mark Nunberg
Mark Nunberg

Reputation: 3701

Because variables.c does not declare variables or preprocessor macros, but actually defines these variables, you will need to make them extern in the "include" phase, and define them in a single file (say, externs_definitions.c).

For example:

variables.h

#ifndef VARIABLES_H
#define VARIABLES_H
extern CHGR_CMD comand[MAX_COMANDS] __attribute__ ((section ("external"))); 
extern RAWDAT rawdat[MAX_RAWDAT] __attribute__ ((section ("external")));     
extern SC_TEST *curr_test[NUMCHANS];   /* array of pointers to current testrec */
...
#endif /* VARIABLES_H_ */

Then leave variables.c as is.

Then in init_vars.c

#include "variables.h"

Further questions though; how does the code work currently? If init_vars.c doesn't directly include variables.c and there's no header file declaring them as extern, how does the existing code not fail the preprocessor trying to access undeclared variables?

Upvotes: 1

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