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Type range errors, including loss of data (truncation) and loss of sign (sign errors), can occur when converting from a value of a signed type to a value of an unsigned type. This noncompliant code example results in a loss of sign:negative number being misinterpreted as a large positive number.

#include <limits.h>

void func(void) {
  signed int si = INT_MIN;) {
  /* Cast eliminates warning */
  unsigned int ui = (unsigned int)si;

  /* ... */
}

/* ... */

func(INT_MIN);

Compliant Solution (Signed to Unsigned)

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#include <limits.h>

void func(void) {
  signed int si = INT_MIN;) {
  unsigned int ui;
  if (si < 0) {
    /* Handle error */
  } else {
    ui = (unsigned int)si;  /* Cast eliminates warning */
  }
  /* ... */
}
/* ... */

func(INT_MIN + 1);

Subclause 6.2.5, paragraph 9, of the C Standard [ISO/IEC 9899:2011] provides the necessary guarantees to ensure this solution works on a conforming implementation:

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