/* gcc acosh.c
 * expected output: acosh(-1) = 0.0000 +3.1416i
 * output on musl:  acosh(-1) = -0.0000 +3.1416i
 */
#include <stdio.h>
#include <complex.h>

int main() {
  double complex arg = -1;
  double complex res = cacosh(arg);
  printf("acosh(-1) = %.4lf %+.4lfi\n", creal(res), cimag(res));
}