MISRA C:2012 Rule 10.6

The value of a composite expression shall not be assigned to an object with wider essential type

Description

Note

Using Code Prover for checking coding rules is no longer supported. See Version History.

Rule Definition

The value of a composite expression shall not be assigned to an object with wider essential type.

Rationale

A composite expression is a nonconstant expression using a composite operator. In the Essential Type Model, composite operators are:

Multiplicative (*, /, %)
Additive (binary +, binary -)
Bitwise (&, |, ^)
Shift (<<, >>)
Conditional (?, :)

Unary operators such as ~ and unary + or - are also considered composite operators.

If you assign the result of a composite expression to a larger type, the implicit conversion can result in loss of value, sign, precision, or layout.

For more information on essential types, see Essential Types in MISRA C Rules 10.x.

Troubleshooting

If you expect a rule violation but do not see it, refer to Diagnose Why Coding Standard Violations Do Not Appear as Expected.

Check Information

Group: The Essential Type Model

Category: Required

AGC Category: Advisory

Version History

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R2024a: Using Code Prover to check for coding rule violations is no longer supported

Checking for coding rule violations and computing code metrics by using Code Prover is no longer supported. To check for coding rule violations and to compute code metrics, use Bug Finder. See Migrate Code Prover Workflows for Checking Coding Standards and Code Metrics to Bug Finder.

R2022a: Using Code Prover to check for coding rule violations is not recommended

Checking for coding rule violations and computing code metrics by using Code Prover is not recommended. This workflow will be removed in a future release. To check for coding rule violations and to compute code metrics, use Bug Finder. See Migrate Code Prover Workflows for Checking Coding Standards and Code Metrics to Bug Finder. To see how Bug Finder checks this rule, see MISRA C:2012 Rule 10.6.

R2021b: Checker flags unary operations whose output is assigned to wider essential types

The checker now flags unary composite operators when their output is assigned to an object with a wider essential type. For instance:

#include<stdint.h>
void foo(uint8_t u8a, uint16_t u16a){
   u8a = ~u8a;                       /* Compliant*/
   u16a = ~u8a;                      /* Noncompliant */
  
}