bits wrap when leftshifting non-constant amounts

[Oliver Fromme]

deeptech71 at gmail.com wrote:
 > My gcc 3.4.6 behaves weirdly when left shifting, and I couldn't
 > find any info on this.
 > [...]
 > It seems that lsh is first moduloed with the width of int. What the hell?

C99 standard, section 6.5.7 "Bitwise shift operators",
page 84:

"If the value of the right operand is negative or is
greater than or equal to the width of the promoted left
operand, the behaviour is undefined."

Best regards
   Oliver

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