[libstdc++] [testsuite] expect zero entropy matching implementation

[Alexandre Oliva <oliva@adacore.com>]

random_device::get_entropy() returns 0.0 when _GLIBCXX_USE_DEV_RANDOM
is not defined, but the test expects otherwise.  Adjust.

Regstrapped on x86_64-linux-gnu, also tested on aarch64-rtems6.  Ok to
install?


for  libstdc++-v3/ChangeLog

	* testsuite/26_numerics/random/random_device/entropy.cc:
        Expect get_entropy to return zero when _GLIBCXX_USE_DEV_RANDOM
        is not defined.
---
 .../26_numerics/random/random_device/entropy.cc    |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

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 9f529f5d81410..3e6872c8a613f 100644
--- a/libstdc++-v3/testsuite/26_numerics/random/random_device/entropy.cc
+++ b/libstdc++-v3/testsuite/26_numerics/random/random_device/entropy.cc
@@ -13,7 +13,13 @@ test01()
       VERIFY( std::random_device(token).entropy() == 0.0 );
 
   using result_type = std::random_device::result_type;
+#ifdef _GLIBCXX_USE_DEV_RANDOM
   const double max = std::numeric_limits<result_type>::digits;
+#else
+  // random_device::entropy() always returns 0.0 when
+  // _GLIBCXX_USE_DEV_RANDOM is not defined.
+  const double max = 0.0;
+#endif
 
   for (auto token : { "/dev/random", "/dev/urandom" })
     if (__gnu_test::random_device_available(token))
@@ -30,7 +36,7 @@ test01()
       VERIFY( entropy == max );
     }
 
-    for (auto token : { "getentropy", "arc4random" })
+  for (auto token : { "getentropy", "arc4random" })
     if (__gnu_test::random_device_available(token))
     {
       const double entropy = std::random_device(token).entropy();

-- 
Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
   Free Software Activist                       GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts.  Ask me about <https://stallmansupport.org>