V3542. AUTOSAR. Constant expression evaluation should not result in an unsigned integer wrap-around.

This diagnostic rule is based on the software development guidelines developed by AUTOSAR (AUTomotive Open System ARchitecture).

As specified by the C++ standard, an overflow of values of unsigned types results in a wrap-around. Using this mechanism in evaluation of expressions at runtime is a well-known practice (unlike signed types, where an overflow leads to undefined behavior).

However, an unsigned integer wrap-around in expressions evaluated at compile time may be misleading.

Example of non-compliant code:

#include <stdint.h>
#define C1 (UINT_MAX) 
#define C2 (UINT_MIN) 
....
void foo(unsigned x)
{
    switch(x)
    {
        case C1 + 1U: ....; break;
        case C2 - 1U: ....; break;
    }
}

According to this rule, an unsigned integer wrap-around that occurs when evaluating a constant expression of unsigned type, it will not be treated as an error if the expression will never be evaluated:

#include <stdint.h>
#define C UINT_MAX
....
unsigned foo(unsigned x)
{
    if(x < 0 && (C + 1U) == 0x42) ....;  
    return x + C; 
}

The '(C + 1U)' expression resulting in an overflow will not be executed since the 'x < 0' condition is always true. Therefore, the second operand of the logical expression will not be evaluated.

This diagnostic is classified as:

Was this page helpful?

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

If you can’t find an answer to your question, fill in the form below and our developers will contact you

By clicking this button you agree to our Privacy Policy statement