Fwd: PATCH: OpenBSD requires special hoops to get correct random numbers

Fwd: PATCH: OpenBSD requires special hoops to get correct random numbers

[Mikael Magnusson]

Apparently gmail decided to eat the original message?


---------- Forwarded message ----------
From: Mikael Magnusson <mikachu@gmail.com>
Date: Tue, Aug 9, 2016 at 10:15 PM
Subject: PATCH: OpenBSD requires special hoops to get correct random numbers
To: zsh-workers@zsh.org


Apparently there was a change in OpenBSD fairly recently[1] that
causes random numbers generated by rand() to ignore the value passed to
srand(). Since zsh guarantees repeatable sequences we have to use their
non-standard interface to continue providing this guarantee.

If someone has an opinion on where to stick the #define or if the two
call-sites should be explicitly #ifdef'd, let me know.

At home,
% zsh -c 'repeat 3 { RANDOM=5; echo $RANDOM }'
23835
23835
23835
On OpenBSD system,
% zsh -c 'repeat 3 { RANDOM=5; echo $RANDOM }'
24254
32257
4161
On OpenBSD system with patch applied,
% Src/zsh -c 'repeat 3 { RANDOM=5; echo $RANDOM }'
14426
14426
14426

[1] http://marc.info/?l=openbsd-cvs&m=141807513728073&w=2

---

 Src/zsh_system.h | 4 ++++
 configure.ac     | 3 ++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/Src/zsh_system.h b/Src/zsh_system.h
index 17c4c64..a9cbf02 100644
--- a/Src/zsh_system.h
+++ b/Src/zsh_system.h
@@ -882,6 +882,10 @@ extern short ospeed;
 # endif
 #endif

+#ifdef HAVE_SRAND_DETERMINISTIC
+# define srand srand_deterministic
+#endif
+
 #ifdef ZSH_VALGRIND
 # include "valgrind/valgrind.h"
 # include "valgrind/memcheck.h"
diff --git a/configure.ac b/configure.ac
index 3e9e467..6ee5c5d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1322,7 +1322,8 @@ AC_CHECK_FUNCS(strftime strptime mktime timelocal \
               realpath canonicalize_file_name \
               symlink getcwd \
               cygwin_conv_path \
-              nanosleep)
+              nanosleep \
+              srand_deterministic)
 AC_FUNC_STRCOLL

 AH_TEMPLATE([REALPATH_ACCEPTS_NULL],
--
2.8.2



-- 
Mikael Magnusson

Re: PATCH: OpenBSD requires special hoops to get correct random numbers

[Peter Stephenson]

On Wed, 10 Aug 2016 17:03:16 +0200
Mikael Magnusson <mikachu@gmail.com> wrote:
> If someone has an opinion on where to stick the #define or if the two
> call-sites should be explicitly #ifdef'd, let me know.

Looks OK to me, given the nature of the problem.

pws