[CUDA] Disallow variadic functions other than printf in device code.

[tra]

Small nit. LGTM otherwise.

lib/Sema/SemaDecl.cpp

8291–8293

It would be nice to emit this diagnostics on one side of compilation only.

Nit - unneeded {}

[jlebar]

Add check for extern "C" printf -- we don't want to take just any printf!

lib/Sema/SemaDecl.cpp

8291–8293

Resolved irl.

include/clang/Basic/DiagnosticSemaKinds.td

def warn_host_calls_from_host_device : Warning<
   "calling __host__ function %0 from __host__ __device__ function %1 can lead to runtime errors">,
   InGroup<CudaCompat>;
 def warn_kern_is_method : Extension<
   "kernel function %0 is a member function; this may not be accepted by nvcc">,
   InGroup<CudaCompat>;
 def warn_kern_is_inline : Warning<
   "ignored 'inline' attribute on kernel function %0">,
   InGroup<CudaCompat>;
+def err_variadic_device_fn : Error<
+  "CUDA device code does not support variadic functions">;
 def err_va_arg_in_device : Error<
   "CUDA device code does not support va_arg">;
 
 def warn_non_pod_vararg_with_format_string : Warning<
   "cannot pass %select{non-POD|non-trivial}0 object of type %1 to variadic "
   "%select{function|block|method|constructor}2; expected type from format "
   "string was %3">, InGroup<NonPODVarargs>, DefaultError;
 // The arguments to this diagnostic should match the warning above.

lib/Sema/SemaDecl.cpp

if (getLangOpts().OpenCLVersion >= 200) {
             D.setInvalidType();
           }
       }
     }
   }
 
   MarkUnusedFileScopedDecl(NewFD);
 
-  if (getLangOpts().CUDA)
-    if (IdentifierInfo *II = NewFD->getIdentifier())
-      if (!NewFD->isInvalidDecl() &&
-          NewFD->getDeclContext()->getRedeclContext()->isTranslationUnit()) {
-        if (II->isStr("cudaConfigureCall")) {
-          if (!R->getAs<FunctionType>()->getReturnType()->isScalarType())
-            Diag(NewFD->getLocation(), diag::err_config_scalar_return);
+  if (getLangOpts().CUDA) {
+    IdentifierInfo *II = NewFD->getIdentifier();
+    if (II && II->isStr("cudaConfigureCall") && !NewFD->isInvalidDecl() &&
 
-          Context.setcudaConfigureCallDecl(NewFD);
-        }
-      }
-  
+
+    // Variadic functions, other than a *declaration* of printf, are not allowed
+    // in device-side CUDA code.
+    if (NewFD->isVariadic() && (NewFD->hasAttr<CUDADeviceAttr>() ||
+                                NewFD->hasAttr<CUDAGlobalAttr>()) &&
+        !(II && II->isStr("printf") && NewFD->isExternC() &&
+          !D.isFunctionDefinition())) {
+      Diag(NewFD->getLocation(), diag::err_variadic_device_fn);
+    }
   // Here we have an function template explicit specialization at class scope.
   // The actually specialization will be postponed to template instatiation
   // time via the ClassScopeFunctionSpecializationDecl node.
   if (isDependentClassScopeExplicitSpecialization) {
     ClassScopeFunctionSpecializationDecl *NewSpec =
                          ClassScopeFunctionSpecializationDecl::Create(
                                 Context, CurContext, SourceLocation(), 
                                 cast<CXXMethodDecl>(NewFD),

test/SemaCUDA/vararg.cu

 // REQUIRES: x86-registered-target
 // REQUIRES: nvptx-registered-target
 // RUN: %clang_cc1 -triple nvptx64-nvidia-cuda -fcuda-is-device -fsyntax-only \
 // RUN:   -verify -DEXPECT_ERR %s
-// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only -verify %s
 
 #include <stdarg.h>
 #include "Inputs/cuda.h"
 
 __device__ void foo() {
   va_list list;
   va_arg(list, int);
 #ifdef EXPECT_ERR
   // expected-error@-2 {{CUDA device code does not support va_arg}}
 #endif
 }
 
 void bar() {
   va_list list;
   va_arg(list, int);  // OK: host-only
 }
 
 __device__ void baz() {
 #if !defined(__CUDA_ARCH__)
   va_list list;
   va_arg(list, int);  // OK: only seen when compiling for host
 #endif
 }
+
+__device__ void vararg(const char* x, ...) {}
+// expected-error@-1 {{CUDA device code does not support variadic functions}}
+
+extern "C" __device__ int printf(const char* fmt, ...);  // OK, special case.
+
+// Definition of printf not allowed.
+extern "C" __device__ int printf(const char* fmt, ...) { return 0; }
+// expected-error@-1 {{CUDA device code does not support variadic functions}}
+
+namespace ns {
+__device__ int printf(const char* fmt, ...);
+// expected-error@-1 {{CUDA device code does not support variadic functions}}
+}