Re: Word For Today: “Uglification”

scott@slp53.sl.home (Scott Lurndal) writes:

Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

For context, here's the entire file from my system (Ubuntu 24.0.4,
package libc6-dev:amd64 2.35-0ubuntu3.6).  I get the impression that the
author(s) decided not to use memset to avoid the required #include,
which might increase compilation times for code that indirectly includes
this header.  (I offer no opinion on whether that's a good tradeoff.)
>
Note that __FD_ZERO is very clearly *not* intended to be invoked by
arbitrary code.
>
```

[code snipped]

```
>

>
That code is only selected if it is not compiled with
gcc.  If it is gcc 2 or later, the header file uses
>
# define __FD_ZERO(fdsp) \
  do {                                                                        \
    int __d0, __d1;                                                           \
    __asm__ __volatile__ ("cld; rep; " __FD_ZERO_STOS                         \
                          : "=c" (__d0), "=D" (__d1)                          \
                          : "a" (0), "0" (sizeof (fd_set)                     \
                                          / sizeof (__fd_mask)),              \
                            "1" (&__FDS_BITS (fdsp)[0])                       \
                          : "memory");                                        \
  } while (0)

Oh?  I don't see that code anywhere in the current glibc sources, in any
older version of bits/select.h, or anywhere under /usr/include on my
system.

--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Medtronic
void Void(void) { Void(); } /* The recursive call of the void */