/**
 * @name Narrowing conversions
 * @description Find all narrowing conversions from a larger integer type,
 *              such as uint32_t, to a smaller integer type, such as uint8_t.
 * @kind problem
 */

import cpp
import semmle.code.cpp.ir.IR

/** Holds if `i` is a narrowing conversion. */
predicate isNarrowingConversion(ConvertInstruction i) {
  i.getResultSize() < i.getUnary().getResultSize()
}

from ConvertInstruction conv, Type inputType, Type outputType
where
  isNarrowingConversion(conv) and
  inputType = conv.getUnary().getResultType() and
  outputType = conv.getResultType()
select conv, "Narrowing conversion from " + inputType + " to " + outputType + "."