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 do not see the email in your inbox, please check if it is filtered to one of the following folders:

  • Promotion
  • Updates
  • Spam

Webinar: Parsing C++ - 10.10

>
>
>
V2543. MISRA. Value of the essential ch…
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

V2543. MISRA. Value of the essential character type should be used appropriately in the addition/subtraction operations.

Jun 18 2019

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

This diagnostic rule is only relevant for C. Values of the essential character type should not be used in arithmetic expressions.

The MISRA standard defines the following essential type model, in which a variable may have a type:

  • Boolean, if it operates true/false values: '_Bool';
  • signed, if operates signed integer numbers, or is an unnamed enum: 'signed char', 'signed short', 'signed int', 'signed long', 'signed long long', 'enum { .... }';
  • unsigned, if operates unsigned integer numbers: 'unsigned char', 'unsigned short', 'unsigned int', 'unsigned long', 'unsigned long long';
  • floating, if operates floating point numbers: 'float', 'double', 'long double';
  • character, if operates only characters: 'char';
  • Named enum, if operates a named set of user-specific values: 'enum name { .... };'.

There are no pointers in this model.

According to the essential type model, essential character type values mustn't be used in arithmetic expressions, as they are represented by a non-numerical type.

Let's see the list of correct ways of using character-type variables in arithmetic expressions:

  • When adding, one operand must have the character type, another one - of signed or unsigned integer type. The result of such operation has the character type:
    • character + [un]signed => character; (1)
    • [un]signed + character => character; (2)
  • When subtracting, the left operand must have character type and the right operand - the signed or unsigned integer type. The result of this operation will be a value of character type:
    • character - [un]signed => character; (3)
  • When subtracting, both operands must have character type. The result of such operation will be a value of signed integer type:
    • character - character => signed; (4)

An example of the code for which the analyzer will issue warnings:

void foo(char ch, unsigned ui, float f, _Bool b, enum A eA)
{
  ch + f; // Essential character type should not be used in
// the addition operation with expression
// of the essential floating type

ch + b; // Also relates to the essential Boolean

ch + eA; // Also relates to the essential enum <A> type

(ch + ui) + (ch - 6); // After the expressions in parentheses
// have been executed, both operands of the
// essential character type are used
// in addition operation
}

This diagnostic is classified as:

  • MISRA-C-10.2