[gcc r16-6225] libstdc++: Adjust tests to work for -D_GLIBCXX_USE_OLD_GENERATE_CANONICAL

[Jonathan Wakely]

https://gcc.gnu.org/g:53893d44f3fec79134f4b43436a7d591985a711d

commit r16-6225-g53893d44f3fec79134f4b43436a7d591985a711d
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Dec 17 13:58:21 2025 +0000

    libstdc++: Adjust tests to work for -D_GLIBCXX_USE_OLD_GENERATE_CANONICAL
    
    libstdc++-v3/ChangeLog:
    
            * testsuite/26_numerics/random/uniform_real_distribution/operators/64351.cc
            [_GLIBCXX_USE_OLD_GENERATE_CANONICAL]: Restore test01. Do not discard an
            extra value in test02.
            * testsuite/26_numerics/random/uniform_real_distribution/operators/gencanon.cc:
            Skip if _GLIBCXX_USE_OLD_GENERATE_CANONICAL is defined in options.

Diff:
---
 .../uniform_real_distribution/operators/64351.cc   | 25 ++++++++++++++++++++++
 .../operators/gencanon.cc                          |  3 ++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/testsuite/26_numerics/random/uniform_real_distribution/operators/64351.cc b/libstdc++-v3/testsuite/26_numerics/random/uniform_real_distribution/operators/64351.cc
index 80818df855e8..3031984df15a 100644
--- a/libstdc++-v3/testsuite/26_numerics/random/uniform_real_distribution/operators/64351.cc
+++ b/libstdc++-v3/testsuite/26_numerics/random/uniform_real_distribution/operators/64351.cc
@@ -21,6 +21,25 @@
 #include <random>
 #include <testsuite_hooks.h>
 
+// libstdc++/64351
+void
+test01()
+{
+#ifdef _GLIBCXX_USE_OLD_GENERATE_CANONICAL
+  std::mt19937 rng(8890);
+  std::uniform_real_distribution<float> dist;
+
+  rng.discard(30e6);
+  for (long i = 0; i < 10e6; ++i)
+    {
+      auto n = dist(rng);
+      VERIFY( n != 1.f );
+    }
+#else
+  // New generate_canonical is tested in ./gencanon.cc
+#endif
+}
+
 // libstdc++/63176
 void
 test02()
@@ -37,13 +56,19 @@ test02()
 
     rng2.discard(1);
   }
+
   // PR libstdc++/80137
+#ifdef _GLIBCXX_USE_OLD_GENERATE_CANONICAL
+  // Each std::generate_canonical call should consume exactly one value.
+#else
   rng2.discard(1);  // account for a 1.0 generated and discarded.
+#endif
   VERIFY( rng == rng2 );
 }
 
 int
 main()
 {
+  test01();
   test02();
 }
diff --git a/libstdc++-v3/testsuite/26_numerics/random/uniform_real_distribution/operators/gencanon.cc b/libstdc++-v3/testsuite/26_numerics/random/uniform_real_distribution/operators/gencanon.cc
index 40061daa31c0..87ad206a78a4 100644
--- a/libstdc++-v3/testsuite/26_numerics/random/uniform_real_distribution/operators/gencanon.cc
+++ b/libstdc++-v3/testsuite/26_numerics/random/uniform_real_distribution/operators/gencanon.cc
@@ -1,4 +1,5 @@
 // { dg-do run { target { c++11 && { ! simulator } } } }
+// { dg-skip-if "requires new impl" { *-*-* } { -D_GLIBCXX_USE_OLD_GENERATE_CANONICAL -D_GLIBCXX_USE_OLD_GENERATE_CANONICAL=1 } }
 
 #include <random>
 #include <limits>
@@ -17,7 +18,7 @@ struct local_rng : std::mt19937
   local_rng(std::mt19937 const& arg) : std::mt19937(arg) {}
 };
 
-// Verify P0952R9 implementation requiring a second round-trip
+// Verify P0952R2 implementation requiring a second round-trip
 // if first yields exactly 1. In this test, the RNG delivering
 // 32 bits per call is seeded such that this occurs once on the
 // sixth iteration for float, and not at all for double.