#define _GNU_SOURCE
#include <complex.h>
#include <math.h>
#include <stdbool.h>
#include <stdio.h>

double complex
test_clog10(double complex z, bool manpages)
{
  double r;

  if (manpages)
    r = carg(z) / M_LN10;
  else
    r = carg(z);
  return log10(cabs(z)) + r * I;
}

int
main(void) {
  double complex c, r1, r2;

  c = 4 + 5*I;
  r1 = clog10(c);
  r2 = test_clog10(c, false);
  printf("%g + I%g %s %g + I%g\n",
         creal(r1), cimag(r1), r1 == r2 ? "==" : "!=", creal(r2), cimag(r2));
  r2 = test_clog10(c, true);
  printf("%g + I%g %s %g + I%g\n",
         creal(r1), cimag(r1), r1 == r2 ? "==" : "!=", creal(r2), cimag(r2));
  return 0;
}