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V2641. MISRA. Types should be explicitly specified.
This diagnostic rule is based on the MISRA (Motor Industry Software Reliability Association) software development guidelines.
This diagnostic rule is relevant only for C.
The C language enables the declaration of entities without explicitly specifying their type. In such a case, the standard states that the entity type is int. Using such a language feature can lead to confusion or an error.
The example:
// TU1.c
#include <stddef.h>
void *my_malloc (size_t n) { /* Implementation */ }
// TU2.c
#include <stddef.h>
extern my_malloc (size_t n);In the TU1.c file, the my_malloc allocating function, which takes a size in bytes and returns a pointer to the allocated memory is defined. To use this function, developers manually wrote a forward function declaration in the TU2.c file but forgot to specify the return type. As a result, the compiler assumes that the function returns int. This may cause errors during program execution if the pointer size and int size do not match.
To fix the error, specify the data type:
// TU2.c
#include <stddef.h>
extern void *my_malloc (size_t n);The analyzer also issues warnings on the following entity declarations:
extern var1; // variable declaration of 'int' type
func1() {} // function declaration with the no return type
static var2; // variable declaration of 'double' typeThe fixed examples:
extern int var1; // variable declaration of 'int' type
void func1() {} // function declaration with the no return type
static double var2; // variable declaration of 'double' typeThis diagnostic is classified as:
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