[OPENMP]Fix PR47790: segfault in frontend while parsing Objective-C with OpenMP.

[ABataev]

Summary

Need to check if the sema is actually finishing a function decl.

[jdoerfert]

LGTM

clang/lib/Sema/SemaDecl.cpp

Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
   PopFunctionScopeInfo(ActivePolicy, dcl);
   // If any errors have occurred, clear out any temporaries that may have
   // been leftover. This ensures that these temporaries won't be picked up for
   // deletion in some later function.
   if (hasUncompilableErrorOccurred()) {
     DiscardCleanupsInEvaluationContext();
   }
 
-  if (LangOpts.OpenMP || LangOpts.CUDA || LangOpts.SYCLIsDevice) {
+  if (FD && (LangOpts.OpenMP || LangOpts.CUDA || LangOpts.SYCLIsDevice)) {
     auto ES = getEmissionStatus(FD);
     if (ES == Sema::FunctionEmissionStatus::Emitted ||
         ES == Sema::FunctionEmissionStatus::Unknown)
       DeclsToCheckForDeferredDiags.push_back(FD);
   }
 
   return dcl;
 }

clang/test/SemaObjCXX/objcxx_openmp.mm

+// RUN: %clang_cc1 -fopenmp -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+class Foo {
+  int a;
+};
+
+@interface NSObject
+@end
+
+@interface Bar : NSObject {
+  Foo *foo;
+}
+- (void)setSystemAndWindowCocoa:(class Foo *)foo_1;
+
+@end
+
+@implementation Bar : NSObject
+- (void)setSystemAndWindowCocoa:(Foo *)foo_1 {
+  foo = foo_1;
+}
+@end