MISRA C:2012  Rule-8.5:  (Required)			An external object or function shall be declared once in one and only one file

Amplification:

This rule applies to non-defining declarations only.

Example Code:

#include "misra.h"
#include "m3cmex.h"

extern int16_t obj_0805a;                           /* 3447      */
extern int16_t obj_0805b;                           /* 3447      */
extern int16_t obj_0805c;                           /* 3447      */

extern int16_t rule_0805( void );                   /* 3447 3451 */

extern int16_t rule_0805( void )
{
   extern int16_t obj_0805d;                        /* 3447 3222 */
   extern void test0805a(void);                     /* 3447 3221 */

   obj_0805a = 0;
   obj_0805b = 0;

   return 0;
}

QAC messages that encompass this guideline:

1513	Identifier '%1s' with external linkage has separate non-defining declarations in more than one location.
3221	Function with external linkage declared at block scope.
3222	Object with external linkage declared at block scope.
3447	'%s' is being declared with external linkage but this declaration is not in a header file.
3451	The global identifier '%s' has been declared in more than one file.

(c) The Motor Industry Research Association, 2012

QA C Source Code Analyser 8.1.2 MISRA C:2012 Compliance Module 1.0 © 2013 Programming Research www.programmingresearch.com

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