[OpenMP] Add default stub for virtual methods (#174594)

jhuber6 · web-flow · commit 0753286b8e27 · 2026-01-06T08:44:02.000-06:00
Summary:
Recent OpenMP patches have added real support for virtual functions on
the device side. However, we don't provide some of the C++ ABI functions
that are emitted when using these. In practice these functions just call
`std::terminate` so we can just trap here. These are marked weak so they
will be overridden by a more correct implementation if not defined and
will also not extract on their own from a static library.
diff --git a/openmp/device/src/Misc.cpp b/openmp/device/src/Misc.cpp
@@ -136,4 +136,10 @@ unsigned long long __llvm_omp_host_call(void *fn, void *data, size_t size) {
 }
 }
 
+// C++ ABI helpers.
+extern "C" {
+[[gnu::weak]] void __cxa_pure_virtual(void) { __builtin_trap(); }
+[[gnu::weak]] void __cxa_deleted_virtual(void) { __builtin_trap(); }
+}
+
 ///}

Original file line number	Diff line number	Diff line change
`@@ -136,4 +136,10 @@ unsigned long long __llvm_omp_host_call(void fn, void data, size_t size) {`
`136`	`136`	`}`
`137`	`137`	`}`
`138`	`138`
	`139`	`+// C++ ABI helpers.`
	`140`	`+extern "C" {`
	`141`	`+[[gnu::weak]] void __cxa_pure_virtual(void) { __builtin_trap(); }`
	`142`	`+[[gnu::weak]] void __cxa_deleted_virtual(void) { __builtin_trap(); }`
	`143`	`+}`
	`144`	`+`
`139`	`145`	`///}`