Our website uses cookies to enhance your browsing experience.
Accept
to the top
close form

Fill out the form in 2 simple steps below:

Your contact information:

Step 1
Congratulations! This is your promo code!

Desired license type:

Step 2
Team license
Enterprise license
** By clicking this button you agree to our Privacy Policy statement
close form
Request our prices
New License
License Renewal
--Select currency--
USD
EUR
* By clicking this button you agree to our Privacy Policy statement

close form
Free PVS‑Studio license for Microsoft MVP specialists
* By clicking this button you agree to our Privacy Policy statement

close form
To get the licence for your open-source project, please fill out this form
* By clicking this button you agree to our Privacy Policy statement

close form
I am interested to try it on the platforms:
* By clicking this button you agree to our Privacy Policy statement

close form
check circle
Message submitted.

Your message has been sent. We will email you at


If you haven't received our response, please do the following:
check your Spam/Junk folder and click the "Not Spam" button for our message.
This way, you won't miss messages from our team in the future.

>
>
>
V2541. MISRA. Function should not be de…
menu mobile close menu
Analyzer diagnostics
General Analysis (C++)
General Analysis (C#)
General Analysis (Java)
Micro-Optimizations (C++)
Diagnosis of 64-bit errors (Viva64, C++)
Customer specific requests (C++)
MISRA errors
AUTOSAR errors
OWASP errors (C#)
Problems related to code analyzer
Additional information
toggle menu Contents

V2541. MISRA. Function should not be declared implicitly.

Apr 24 2019

This diagnostic rule is based on the software development guidelines developed by MISRA (Motor Industry Software Reliability Association).

This rule only applies to C. In the C language, it is valid to use a function without its prior declaration. However, this usage is dangerous because it can cause incorrect operation of the program.

Let's look at a simple example:

char *CharMallocFoo(int length)
{
  return (char*)malloc(length);
}

Since the header file <stdlib.h> is not included, the C compiler will conclude that the 'malloc' function's return type is 'int'. Incorrect interpretation of return value by the compiler can cause problems when executing a program, including its crash.

If the program is 64-bit, then most likely 32 high bits of the returned address will be lost. So the program will work incorrectly for some time. However when free memory in 4 low gigabytes of address space is run out or significantly fragmented, a buffer outside 4 low gigabytes will be allocated. As the address's high bits are lost, the consequences will be extremely unpleasant and unpredictable. You may find more details about this case in the article "A nice 64-bit error in C".

Correct code:

#include <stdlib.h>
....
char *CharMallocFoo(int length)
{
  return (char*)malloc(length);
}

This diagnostic is classified as:

  • MISRA-C-17.3