Give a warning when defining a task outline but exists a previous declaration that is not.

Closes llvm#84

Author: mikaoP

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -11003,6 +11003,9 @@ def warn_oss_decl_shadow :
           "type alias in %2}1">;
 def warn_oss_decl_shadow_uncaptured_local :
   Warning<warn_oss_decl_shadow.Text>;
+def warn_oss_call_may_not_be_task :
+  Warning<"function has already been declared earlier as a regular (non-task) function, "
+          "any calls prior to this point will not create tasks">;
 } // end of OmpSs component.
 
 

clang/lib/Sema/SemaOmpSs.cpp

@@ -2192,6 +2192,12 @@ Sema::DeclGroupPtrTy Sema::ActOnOmpSsDeclareTaskDirective(
     return DeclGroupPtrTy();
   }
 
+  if (FD->getFirstDecl() != FD) {
+    Diag(ADecl->getLocation(), diag::warn_oss_call_may_not_be_task);
+    Diag(FD->getFirstDecl()->getLocation(), diag::note_previous_decl)
+      << FD->getFirstDecl();
+  }
+
   auto ParI = FD->param_begin();
   while (ParI != FD->param_end()) {
     QualType Type = (*ParI)->getType();

clang/test/OmpSs/Sema/task_outline_late_defined.c

@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -verify -fompss-2 -ferror-limit 100 %s -Wuninitialized
+static void foo(int *p); // expected-note {{'foo' declared here}}
+static void foo(int *p);
+
+int main() {
+    int n;
+    foo(&n);
+    #pragma oss taskwait
+}
+
+#pragma oss task inout(*p)
+static void foo(int *p) { } // expected-warning {{function has already been declared earlier as a regular (non-task) function, any calls prior to this point will not create tasks}}