MISRA C:2012 Rule 8.5

In this example, the declaration of external function func2() is noncompliant because it occurs in a nonheader file. The other external object and function declarations occur in a header file and comply with this rule. To fix this issue, declare func2() in a header file.

Header file:

/* header.h */
extern int var;
extern void func1(void);   /* Compliant */

Source file:

/* module.c */
#include "header.h"

extern void func2(void);   /* Noncompliant */

/* Definitions */
int var = 0;
void func1(void) {}

In this example, the function func() is declared in header1.h. In header2.h, the function is called. In module2.c, the file header2.h is included, but header1.h is not included, perhaps inadvertently. Because module2.c includes a call to func() but no declaration, the compiler generates an implicit declaration for the function during compilation. The file module1.c includes header1.h, which contains an explicit declaration. Having an explicit and an implicit declaration for the same external function is noncompliant with this rule. Polyspace raises a violation. Polyspace reports a defect. In the Result Details section, Polyspace flags :

//header1.h

extern void func(void);

//header2.h

#define __STATIC_INLINE static inline

__STATIC_INLINE void Reset(void)
{
	//...
	func(); //Noncompliant
}

//module1.c
#include "header2.h"
#include "header1.h"

void foo(void)
{
}

//module2.c
#include "header2.h"

void bar(void)
{
}

To fix this violation, include the file header1.h in module2.c.

In this example, the declaration of the function func() is in the header header.h. The source files module1.c and module2.c contains calls to func(), but the header file is not included in these source files, perhaps by mistake. As a result, the compiler creates two implicit declaration of func(), causing a violation of this rule. Polyspace reports the violation. In the Result Details section, Polyspace flags the function calls that trigger the creation of the implicit declarations.

//header.h

extern void func(void);

//module1.c

void foo(void)
{
	func(); //Noncompliant
}

//module2.c

void bar(void)
{
	func(); 
}

To fix this violation, include the file header.h in module1.c and module2.c.