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authorYves Orton <demerphq@gmail.com>2022-08-05 13:18:02 +0200
committerYves Orton <demerphq@gmail.com>2022-08-12 22:29:05 +0200
commitbf2a3dae9f4f828fd1f2f8aaf4769f96520c9552 (patch)
treeb58ad50f0d8d828bb5a890686e0ce7e82ae529ae /pp.c
parent08da5deb5d0c842dab3fe5f4f5a450972a0eb67c (diff)
downloadperl-bf2a3dae9f4f828fd1f2f8aaf4769f96520c9552.tar.gz
Add a new env var PERL_RAND_SEED
This env var can be used to trigger a repeatable run of a script which calls C<srand()> with no arguments, either explicitly or implicitly via use of C<rand()> prior to calling srand(). This is implemented in such a way that calling C<srand()> with no arguments in forks or subthreads (again explicitly or implicitly) will receive their own seed but the seeds they receive will be repeatable. This is intended for debugging and perl development performance testing, and for running the test suite consistently. It is documented that the exact seeds used to initialize the random state are unspecified, and that they may change between releases or even builds. The only guarantee provided is that the same perl executable will produce the same results twice all other things being equal. In practice and in core testing we do expect consistency, but adding the tightest set of restrictions on our commitments seemed sensible. The env var is ignored when perl is run setuid or setgid similarly to the C<PERL_INTERNAL_RAND_SEED> env var.
Diffstat (limited to 'pp.c')
-rw-r--r--pp.c20
1 files changed, 18 insertions, 2 deletions
diff --git a/pp.c b/pp.c
index 2f88019aca..20df361f74 100644
--- a/pp.c
+++ b/pp.c
@@ -2920,7 +2920,17 @@ PP(pp_sin)
PP(pp_rand)
{
if (!PL_srand_called) {
- (void)seedDrand01((Rand_seed_t)seed());
+ Rand_seed_t s;
+ if (PL_srand_override) {
+ /* env var PERL_RAND_SEED has been set so the user wants
+ * consistent srand() initialization. */
+ PERL_SRAND_OVERRIDE_GET(s);
+ } else {
+ /* Pseudo random initialization from context state and possible
+ * random devices */
+ s= (Rand_seed_t)seed();
+ }
+ (void)seedDrand01(s);
PL_srand_called = TRUE;
}
{
@@ -2979,7 +2989,13 @@ PP(pp_srand)
}
}
else {
- anum = seed();
+ if (PL_srand_override) {
+ /* env var PERL_RAND_SEED has been set so the user wants
+ * consistent srand() initialization. */
+ PERL_SRAND_OVERRIDE_GET(anum);
+ } else {
+ anum = seed();
+ }
}
(void)seedDrand01((Rand_seed_t)anum);