[libcxx] [test] Clarify a MinGW test failure waiver in rand.dist.uni.int/eval.pass.cpp

[• Quuxplusone]

I think my comment is worth pursuing, but if it doesn't work out, then I think this is a vast improvement anyway. Thanks!

libcxx/test/std/numerics/rand/rand.dis/rand.dist.uni/rand.dist.uni.int/eval.pass.cpp

136

Is there an easy way to just change this ifdef, assuming it controls the trouble spot in Clang 13?
git grep TEST_BUGGY_SIGNALING_NAN libcxx/test/ to see the approach I'm thinking of.

[mstorsjo]

libcxx/test/std/numerics/rand/rand.dis/rand.dist.uni/rand.dist.uni.int/eval.pass.cpp

136

Oh, indeed, that works (I never checked that far in the source before) and is even nicer.

[mstorsjo]

Use a conditional ifdef to narrow down the workaround as suggested.

[• Quuxplusone]

LGTM if CI is green!
I observe that unfortunately we set TEST_BUGGY_FOO to true exactly when we don't want to test the buggy foo; but I think my original logic there was that TEST_ was a prefix for all test macros, and so the name of the macro was meant to signify "(We're in a) test, and foo is buggy." Anyway, as long as this is consistent with TEST_BUGGY_SIGNALING_NAN, I'm cool with it.

libcxx/test/std/numerics/rand/rand.dis/rand.dist.uni/rand.dist.uni.int/eval.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // REQUIRES: long_tests
-//
-// This fails on MinGW for some unknown reason.
-// UNSUPPORTED: target={{.+}}-windows-gnu
 
 // <random>
 
 // template<class _IntType = int>
 // class uniform_int_distribution
 
 // template<class _URNG> result_type operator()(_URNG& g);
 
 #include <random>
 #include <cassert>
 #include <climits>
 #include <cstddef>
 #include <limits>
 #include <numeric>
 #include <vector>
 
 #include "test_macros.h"
 
+// The __int128 conversions to/from floating point crash on MinGW on x86_64.
+// This is fixed in Clang 14 by https://reviews.llvm.org/D110413.
+#if defined(__x86_64__) && defined(__MINGW32__) && defined(__clang_major__) && __clang_major__ < 14
+ #define TEST_BUGGY_I128_FP
+#endif
+
 template <class T>
 T sqr(T x)
 {
     return x * x;
 }
 
 template <class ResultType, class EngineType>
 void test_statistics(ResultType a, ResultType b)
int main(int, char**)
     // http://eel.is/c++draft/rand.req#genl-1.5
     // The effect of instantiating a template that has a parameter
     // named IntType is undefined unless the corresponding template
     // argument is cv-unqualified and is one of short, int, long,
     // long long, unsigned short, unsigned int, unsigned long,
     // or unsigned long long.
     // (We support __int128 as an extension.)
 
-#ifndef _LIBCPP_HAS_NO_INT128
+#if !defined(_LIBCPP_HAS_NO_INT128) && !defined(TEST_BUGGY_I128_FP)
     test_statistics<__int128_t, std::minstd_rand0>();
     test_statistics<__uint128_t, std::minstd_rand0>();
 
     test_statistics<__int128_t, std::minstd_rand0>(-100, 900);
     test_statistics<__int128_t, std::minstd_rand0>(0, UINT64_MAX);
     test_statistics<__int128_t, std::minstd_rand0>(std::numeric_limits<__int128_t>::min(), std::numeric_limits<__int128_t>::max());
     test_statistics<__uint128_t, std::minstd_rand0>(0, UINT64_MAX);
 #endif
 
     return 0;
 }