From 145ef5e2be28183f2b92b1f81b4d75210b524503 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Thu, 23 Jun 2022 11:58:16 +0100
Subject: libstdc++: Simplify test by not using std::log2

This test uses std::log2 without including <cmath>, but it doesn't need
to use it at all. Just get the number of digits from numeric_limits
instead.

libstdc++-v3/ChangeLog:

	* testsuite/26_numerics/random/random_device/entropy.cc: Use
	numeric_limits<unsigned>::digits.

(cherry picked from commit 78fd15fd4a641cfac28ce60bf43a3e1ca309537b)
---
 libstdc++-v3/testsuite/26_numerics/random/random_device/entropy.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'libstdc++-v3')

diff --git a/libstdc++-v3/testsuite/26_numerics/random/random_device/entropy.cc b/libstdc++-v3/testsuite/26_numerics/random/random_device/entropy.cc
index 63b7043bf9b..9f529f5d814 100644
--- a/libstdc++-v3/testsuite/26_numerics/random/random_device/entropy.cc
+++ b/libstdc++-v3/testsuite/26_numerics/random/random_device/entropy.cc
@@ -1,6 +1,7 @@
 // { dg-do run { target c++11 } }
 
 #include <random>
+#include <limits>
 #include <testsuite_hooks.h>
 #include <testsuite_random.h>
 
@@ -12,7 +13,7 @@ test01()
       VERIFY( std::random_device(token).entropy() == 0.0 );
 
   using result_type = std::random_device::result_type;
-  const double max = std::log2(std::numeric_limits<result_type>::max() + 1.0);
+  const double max = std::numeric_limits<result_type>::digits;
 
   for (auto token : { "/dev/random", "/dev/urandom" })
     if (__gnu_test::random_device_available(token))
-- 
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