Hi Harshit,
On 08.01.21 01:35, Harshit Sharma wrote:
> Although, I agree that 1u << 31 is much better, I believe 1 << 31 is not
> wrong either as long as it is assigned to an 'unsigned int' as the compiler
> performs an implicit conversion from a lower data type to a higher data
> type ('int' to 'unsigned int' in this case).
you are right about the implicit conversion, but this happens too
late. The actual error may happen before the conversion. I guess
mostly because of the way signed numbers are handled in assembler,
compilers usually produce code that results in -2^31 for `1 << 31`.
This -2^31 then implicitly converted to an unsigned is 2^31 which
is what we usually intend.
But the theoretical problem is what happens if the compiler produces
code that does not result in -2^31 for the signed number. As the C
standard implicitly says `1 << 31` is undefined, the compiler can
basically do what it wants and would still be C compliant.
Nico
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