Re: Question about PERL_NO_DEV_RANDOM

On Thu, Jan 22, 2026 at 06:47:24PM -0800, Scott Baker wrote:
> As part of my clean up for Perl_seed() I see we have this weird define
> PERL_NO_DEV_RANDOM. Grepping the source code the ONLY place I see that
> defined is in *dosish.h* which appears to be a config file for building Perl
> for old DOS systems. Do we use *dosish.h *for any modern supported systems?
> 
> The only thing this define does is tell Perl_seed() skip trying to read from
> */dev/urandom*. Since this is for older DOS systems which I don't think we
> support (?) can this check be removed? Without that define in place, even on
> DOS systems, the code will fail to read from */dev/urandom* (because it
> doesn't exist) and fail back to hashing state variables instead.

Win32 is considered DOSISH and dosish.h is included on Win32, from
perl.h:

/* define this once if either system, instead of cluttering up the src */
#if defined(WIN32)
#define DOSISH 1
#endif
...
#ifdef DOSISH
#   if defined(OS2)
#       include "os2ish.h"
#   else
#       include "dosish.h"
#   endif
#elif defined(VMS)
...

Someone building perl on Configure based systems can add
-Accflags=-DPERL_NO_DEV_RANDOM to skip trying /dev/urandom.

> Nothing would change in the codepath, it would just make the code cleaner
> and more readable by having one less obscure define.

It's still in use, so it should stay.

Tony