[PATCH] D27279: Store decls in prototypes on the declarator instead of in the AST

[Reid Kleckner via Phabricator via cfe-commits]

rnk created this revision.
rnk added a reviewer: rsmith.
rnk added subscribers: cfe-commits, jmolloy.

This saves two pointers (!) from FunctionDecl that were being used for
some rare and questionable C-only functionality.  The
DeclsInPrototypeScope ArrayRef was added in r151712 in order to parse
this kind of C code:

  enum e {x, y};
  int f(enum {y, x} n) {
   return x; // should return 1, not 0
  }

The challenge is that we parse 'int f(enum {y, x} n)' it its own
function prototype scope that gets popped before we build the
FunctionDecl for 'f'. The original change was doing two questionable
things:

1. Saving all tag decls introduced in prototype scope on a TU-global

Sema variable. This is problematic when you have cases like this, where
'x' and 'y' shouldn't be visible in 'f':

  void f(void (*fp)(enum { x, y } e)) { /* no x */ }

This patch fixes that, so now 'f' can't see 'x', which is consistent
with GCC.

2. Storing the decls in FunctionDecl in ActOnFunctionDeclarator so that

they could be used in ActOnStartOfFunctionDef. This is just an
inefficient way to move information around. The AST lives forever, but
the list of non-parameter decls in prototype scope is short lived. By
moving this stuff to the Declarator, we get the right (short) lifetime.

As the original change was the author's first major Clang patch, they
can be forgiven.


https://reviews.llvm.org/D27279

Files:
  include/clang/AST/Decl.h
  include/clang/Sema/DeclSpec.h
  include/clang/Sema/Sema.h
  lib/AST/ASTDumper.cpp
  lib/AST/Decl.cpp
  lib/Parse/ParseDecl.cpp
  lib/Parse/ParseExpr.cpp
  lib/Parse/ParseExprCXX.cpp
  lib/Sema/DeclSpec.cpp
  lib/Sema/SemaDecl.cpp
  lib/Sema/SemaType.cpp
  test/Misc/ast-dump-decl.c
  test/PCH/decl-in-prototype.c
  test/Sema/decl-in-prototype.c

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