# 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:

```cpp
// 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:

```cpp
// TU2.c
#include <stddef.h>

extern void *my_malloc (size_t n);
```

The analyzer also issues warnings on the following entity declarations:

```cpp
extern var1; // variable declaration of 'int' type
func1() {}   // function declaration with the no return type
static var2; // variable declaration of 'double' type
```

The fixed examples:

```cpp
extern int var1;    // variable declaration of 'int' type
void func1() {}     // function declaration with the no return type
static double var2; // variable declaration of 'double' type
```