Add warning for attribute-cleanup on function parameter.

[comex]

Summary

When a function parameter is declared __attribute__((cleanup)), neither Clang nor GCC actually executes the cleanup function, but Clang didn't warn about it. For the sake of compatibility, add a warning rather than making the attribute actually work.

[rsmith]

This looks fine to me, though it would be better to express the restrictions as a SubjectList on the attribute definition in include/clang/Basic/Attr.td rather than here in code.

[aaron.ballman]

In D15406#307733, @rsmith wrote:

This looks fine to me, though it would be better to express the restrictions as a SubjectList on the attribute definition in include/clang/Basic/Attr.td rather than here in code.

It would be nice, but the issue is the unwieldy list of diagnostic enumerations for custom subject lists. I would love to find a way to express the diagnostic replacement for %1 as part of tablegen instead of manually.

FWIW, this LGTM as well.

~Aaron

[aaron.ballman]

I committed a different fix for this in r319555.

lib/Sema/SemaDeclAttr.cpp

static void handleTargetAttr(Sema &S, Decl *D, const AttributeList &Attr) {
   TargetAttr *NewAttr =
       ::new (S.Context) TargetAttr(Attr.getRange(), S.Context, Str, Index);
   D->addAttr(NewAttr);
 }
 
 
 static void handleCleanupAttr(Sema &S, Decl *D, const AttributeList &Attr) {
   VarDecl *VD = cast<VarDecl>(D);
-  if (!VD->hasLocalStorage()) {
+  if (!VD->hasLocalStorage() || isa<ParmVarDecl>(VD)) {
     S.Diag(Attr.getLoc(), diag::warn_attribute_ignored) << Attr.getName();
     return;
   }
 
   Expr *E = Attr.getArgAsExpr(0);
   SourceLocation Loc = E->getExprLoc();
   FunctionDecl *FD = nullptr;
   DeclarationNameInfo NI;

test/Sema/attr-cleanup.c

 void c5(void*) __attribute__((deprecated));  // expected-note{{'c5' has been explicitly marked deprecated here}}
 void t5() {
   int i __attribute__((cleanup(c5)));  // expected-warning {{'c5' is deprecated}}
 }
 
 void t6(void) {
   int i __attribute__((cleanup((void *)0)));  // expected-error {{'cleanup' argument is not a function}}
 }
+
+void t7(__attribute__((cleanup(c4))) int a) {} // expected-warning {{'cleanup' attribute ignored}}