New comment by tornaria on void-packages repository

https://github.com/void-linux/void-packages/pull/44529#issuecomment-1599570276

Comment:
Actually, this seems like a bug in musl libm:
```
$ cat cacosh.c 
#include <complex.h>
#include <stdio.h>

void main()
{
    double complex z = -1 -I, c;

    c = cacosh(z);

    printf("cacosh(z) = %6.3f %6.3f*i\n", creal(c), cimag(c));
}
$ cc cacosh.c -o cacosh -lm && ./cacosh                          
cacosh(z) = -1.061  2.237*i
```

Note that `cacosh(3p)` says:
```
RETURN VALUE
       These functions shall return the complex arc hyperbolic cosine value,
       in the range of a half-strip of non-negative values along the real axis
       and in the interval [-iπ, +iπ] along the imaginary axis.
```

For whatever reason `cmath.acosh` is not catching this error (probably because it's not using C99 complex trig functions but reimplementing them from C89 real functions).