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stdlib: Test for expected sequence of random numbers from rand

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As the test comment explains, this test is not quite valid, but
preserving the exact sequences helps distributions to port to
newer glibc versions.  We can remove this test if we ever switch
to a different implementation.

Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
This commit is contained in:
Florian Weimer 2025-01-20 21:06:59 +01:00
parent 33b684e019
commit 1ac28b7818
2 changed files with 58 additions and 0 deletions
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1
stdlib/Makefile
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@ -296,6 +296,7 @@ tests := \
tst-qsort3 \
tst-qsort6 \
tst-quick_exit \
tst-rand-sequence \
tst-rand48 \
tst-rand48-2 \
tst-random \

57
stdlib/tst-rand-sequence.c Normal file
View file

@ -0,0 +1,57 @@
/* Test that rand () evaluates to a special expected sequence.
Copyright (C) 2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
/* This test is borderline invalid because the rand function is not
guaranteed to produce the same sequence of numbers on every
architecture or glibc build. However, some software packages have
test suites that depend on the specific sequence of numbers return
here, so this test verifies that they do not change unexpectedly. */
#include <stdlib.h>
#include <support/check.h>
static int
do_test (void)
{
TEST_COMPARE (rand (), 1804289383);
TEST_COMPARE (rand (), 846930886);
TEST_COMPARE (rand (), 1681692777);
TEST_COMPARE (rand (), 1714636915);
TEST_COMPARE (rand (), 1957747793);
TEST_COMPARE (rand (), 424238335);
TEST_COMPARE (rand (), 719885386);
TEST_COMPARE (rand (), 1649760492);
TEST_COMPARE (rand (), 596516649);
TEST_COMPARE (rand (), 1189641421);
srand (1009);
TEST_COMPARE (rand (), 176208083);
TEST_COMPARE (rand (), 1650100842);
TEST_COMPARE (rand (), 1813188575);
TEST_COMPARE (rand (), 2064804480);
TEST_COMPARE (rand (), 1944264725);
TEST_COMPARE (rand (), 1673642853);
TEST_COMPARE (rand (), 1582759448);
TEST_COMPARE (rand (), 309901569);
TEST_COMPARE (rand (), 444031692);
TEST_COMPARE (rand (), 1926035991);
return 0;
}
#include <support/test-driver.c>