Typecasting from signed to unsigned and vis-verse

Typecasting from signed to unsigned and vis-verse - Printable Version

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Typecasting from signed to unsigned and vis-verse - deepabagalkot - 31-07-2014

Hi,

Please can anybody help me to understand whether Misra C rules support signed to unsigned and vis-verse data typecasting?

If there is requirement to do some manipulation on signed and unsigned values, then i think it is ok to type-caste. But the requirement given to us says that whenever there is typecasting happening from signed to unsigned and vis-verse, then such incident should be failed.

Thanks in advance,
Deepa

Re: Typecasting from signed to unsigned and vis-verse - misra-c - 22-08-2014

Rule 10.1 of MISRA C:2004 prohibits implicit conversions for signed to unsigned and vice versa

There are no restrictions on explicit casts between simple signed and unsigned expressions ( and vice versa ). For example:

Code:
UINT_8 u8 = ....

   SINT_8 s8 = ....

   u8 = s8;            /* violates 10.1 */

   u8 = (UINT_8)s8;   /* MISRA compliant */

Casting a complex expression requires the addition of an extra line.

Code:
SINT_8 stemp;  

   u8 = (UINT_8)(s8 + s8);    /* violates 10.3 */

   stemp = s8 + s8;

   u8 = (UINT_8)stemp;       /*  MISRA compliant */