TMS320F28069: Undefined behaviour of left shift?

Shubham Kant Dubey

Intellectual 980 points

Part Number: TMS320F28069

Hi,

I am doing an left shift operation and it is working in rotation. (Using compiler version TI v16.9.4.LTS)

temp1 = (Uint32)(0x3UL << 56);

I am getting result this.

temp1 = 50331648 (00000011000000000000000000000000b)

Result should be this

temp1 = 0

Please explain this undefined behavior of left shift.

Regards,

Shubham

over 5 years ago

0 KARTHIKEYAN RAJAMANICKAM over 5 years ago

TI__Genius 11645 points

Hi,

One of our experts will get back to you on this soon, mostly by Monday 6th July due to US Holidays.

0 George Mock over 5 years ago

TI__Guru**** 251880 points

Any shift expression is undefined when the value of the shift count is greater or than equal to the size, in bits, of the first operand. In this specific case, 31 is the largest defined shift count. 31 is the largest unsigned value which fits within 5 bits. Note the lower 5 bits of the value 56 is 24, the amount of shift which occurred.

Thanks and regards,

-George

C2000™︎ microcontrollers

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TMS320F28069: Undefined behaviour of left shift?