[clang] [CUDA][HIP] Add a __device__ version of std::__glibcxx_assert_fail() (PR #136133)

[Artem Belevich via cfe-commits]

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@@ -0,0 +1,35 @@
+// libstdc++ uses the non-constexpr function std::__glibcxx_assert_fail()
+// to trigger compilation errors when the __glibcxx_assert(cond) macro
+// is used in a constexpr context.
+// Compilation fails when using code from the libstdc++ (such as std::array) on
+// device code, since these assertions invoke a non-constexpr host function from
+// device code.
+//
+// To work around this issue, we declare our own device version of the function
+
+#ifndef __CLANG_CUDA_WRAPPERS_BITS_CPP_CONFIG
+#define __CLANG_CUDA_WRAPPERS_BITS_CPP_CONFIG
+
+#include_next <bits/c++config.h>
+
+#ifdef _LIBCPP_BEGIN_NAMESPACE_STD
+_LIBCPP_BEGIN_NAMESPACE_STD
+#else
+namespace std {
+#ifdef _GLIBCXX_BEGIN_NAMESPACE_VERSION
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+#endif
+#endif
+__device__
+    __attribute__((__always_inline__, __visibility__("default"))) inline void
+    __glibcxx_assert_fail() {}
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Artem-B wrote:

> This fails in fact. It's a "trick" to trigger a compilation failure on a constantly evaluated context: the code ends up calling a non-constexpr function from a constantly evaluated context when the assertion fails.
>
> The new thing in this libstdc++ version is that even when assertions are disabled, on a constexpr context, we still have assert checks.

Would it be possible to create a simple reproducer on godbolt.org? I think I'm missing some bits of this puzzle.


https://github.com/llvm/llvm-project/pull/136133