Emit diagnostic when kernel names use nullptr_t

Author: jtmott-intel

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -10675,7 +10675,8 @@ def err_sycl_attribute_address_space_invalid : Error<
   "address space is outside the valid range of values">;
 def err_sycl_kernel_incorrectly_named : Error<
   "kernel %select{name is missing"
-  "|needs to have a globally-visible name}0">;
+  "|needs to have a globally-visible name"
+  "|name cannot be or use std::nullptr_t}0">;
 def err_sycl_restrict : Error<
   "SYCL kernel cannot "
 "%select{use a non-const global variable"

clang/lib/Sema/SemaSYCL.cpp

@@ -1744,8 +1744,16 @@ void SYCLIntegrationHeader::emitForwardClassDecls(
     ;
   const CXXRecordDecl *RD = T->getAsCXXRecordDecl();
 
-  if (!RD)
+  if (!RD) {
+    // Most non-class types such as `int` can safely skip forward declarations,
+    // but `std::nullptr_t` is a special case that doesn't behave well.
+    if (T->isNullPtrType()) {
+      Diag.Report(KernelLocation, diag::err_sycl_kernel_incorrectly_named)
+          << /* name cannot be or use std::nullptr_t */ 2;
+    }
+
     return;
+  }
 
   // see if this is a template specialization ...
   if (const auto *TSD = dyn_cast<ClassTemplateSpecializationDecl>(RD)) {
@@ -1823,10 +1831,8 @@ void SYCLIntegrationHeader::emit(raw_ostream &O) {
   O << "// This is auto-generated SYCL integration header.\n";
   O << "\n";
 
-  O << "#include <cstddef>\n";
   O << "#include <CL/sycl/detail/defines.hpp>\n";
   O << "#include <CL/sycl/detail/kernel_desc.hpp>\n";
-  O << "using nullptr_t = std::nullptr_t;\n";
 
   O << "\n";
 

clang/test/CodeGenSYCL/stdtypes_kernel_type.cpp

@@ -1,23 +1,19 @@
+// RUN: %clang_cc1 -fsycl -fsycl-is-device -fsycl-int-header=%t.h -DNULLPTRT_CHECK -verify %s
 // RUN: %clang_cc1 -fsycl -fsycl-is-device -fsycl-int-header=%t.h %s
 // RUN: FileCheck -input-file=%t.h %s
 //
-// CHECK: #include <cstddef>
-// CHECK-NEXT: #include <CL/sycl/detail/defines.hpp>
+// CHECK: #include <CL/sycl/detail/defines.hpp>
 // CHECK-NEXT: #include <CL/sycl/detail/kernel_desc.hpp>
-// CHECK-NEXT: using nullptr_t = std::nullptr_t;
 //
 // CHECK: static constexpr
 // CHECK-NEXT: const char* const kernel_names[] = {
-// CHECK-NEXT:   "_ZTSDn"
 // CHECK-NEXT:   "_ZTSSt4byte"
 // CHECK-NEXT:   "_ZTSm",
 // CHECK-NEXT:   "_ZTSl"
 // CHECK-NEXT: };
 //
 // CHECK: static constexpr
 // CHECK-NEXT: const kernel_param_desc_t kernel_signatures[] = {
-// CHECK-NEXT:   //--- _ZTSDn
-// CHECK-EMPTY:
 // CHECK-NEXT:   //--- _ZTSSt4byte
 // CHECK-EMPTY:
 // CHECK-NEXT:   //--- _ZTSm
@@ -28,13 +24,11 @@
 //
 // CHECK: static constexpr
 // CHECK-NEXT: const unsigned kernel_signature_start[] = {
-// CHECK-NEXT:  0, // _ZTSDn
-// CHECK-NEXT:  1, // _ZTSSt4byte
-// CHECK-NEXT:  2, // _ZTSm
-// CHECK-NEXT:  3 // _ZTSl
+// CHECK-NEXT:  0, // _ZTSSt4byte
+// CHECK-NEXT:  1, // _ZTSm
+// CHECK-NEXT:  2 // _ZTSl
 // CHECK-NEXT: };
 
-// CHECK: template <> struct KernelInfo<nullptr_t> {
 // CHECK: template <> struct KernelInfo<::std::byte> {
 // CHECK: template <> struct KernelInfo<unsigned long> {
 // CHECK: template <> struct KernelInfo<long> {
@@ -55,7 +49,10 @@ __attribute__((sycl_kernel)) void kernel_single_task(Func kernelFunc) {
 }
 
 int main() {
-  kernel_single_task<std::nullptr_t>([]() { usage(); });
+#ifdef NULLPTRT_CHECK
+  // expected-error@+1 {{kernel name cannot be or use std::nullptr_t}}
+  kernel_single_task<std::nullptr_t>([=]() {});
+#endif
   kernel_single_task<std::byte>([=]() {});
   kernel_single_task<std::size_t>([=]() {});
   kernel_single_task<std::ptrdiff_t>([=]() {});