[v3,of,08/14] cp/tree.c: strip location wrappers in lvalue_kind

On Wed, 2017-12-20 at 23:56 -0500, Jason Merrill wrote:
> On Wed, Dec 20, 2017 at 5:14 PM, David Malcolm <dmalcolm@redhat.com>
> wrote:
> > On Mon, 2017-12-11 at 18:39 -0500, Jason Merrill wrote:
> > > On 11/10/2017 04:45 PM, David Malcolm wrote:
> > > > Without this, then lvalue_p returns false for decls, and hence
> > > > e.g. uses of them for references fail.
> > > > 
> > > > Stripping location wrappers in lvalue_kind restores the correct
> > > > behavior of lvalue_p etc.
> > > > 
> > > > gcc/cp/ChangeLog:
> > > >     * tree.c (lvalue_kind): Strip any location wrapper.
> > > 
> > > Rather, lvalue_kind should learn to handle VIEW_CONVERT_EXPR.
> > This patch does so, using:
> > 
> >     case NON_LVALUE_EXPR:
> >     case VIEW_CONVERT_EXPR:
> >       if (location_wrapper_p (ref))
> >         return lvalue_kind (TREE_OPERAND (ref, 0));
> > 
> > As well as the VIEW_CONVERT_EXPR, lvalue_kind needs to handle
> > NON_LVALUE_EXPR, otherwise a location-wrapped string literal
> > hits this clause in the "default" case:
> > 
> >       if (CLASS_TYPE_P (TREE_TYPE (ref))
> >           || TREE_CODE (TREE_TYPE (ref)) == ARRAY_TYPE)
> >         return clk_class;
> > 
> > when it should have hit this one (after removing the
> > location wrapper):
> > 
> >     case STRING_CST:
> >     case COMPOUND_LITERAL_EXPR:
> >       return clk_ordinary;
> 
> Ah, the issue is that string literals should use VIEW_CONVERT_EXPR
> rather than NON_LVALUE_EXPR, since they are lvalues.  With that
> change, we shouldn't need to handle NON_LVALUE_EXPR specifically.
> 
> Jason

Thanks.  Here's an updated version of the patch which tweaks
maybe_wrap_with_location (from patch 02/14 [1]) for STRING_CST to do so,
also adding some more test coverage to selftest::test_location_wrappers
for the STRING_CST case.  With that, it only adds the VIEW_CONVERT_EXPR
case to lvalue_kind.

Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu, as
part of the kit.
Manually tested with "make s-selftest-c++" (since we don't run
the selftests for cc1plus by default).

OK for trunk once the rest of the kit is approved?

[1] https://gcc.gnu.org/ml/gcc-patches/2017-11/msg02611.html

gcc/cp/ChangeLog:
	* cp-lang.c (selftest::run_cp_tests): Call
	selftest::cp_tree_c_tests.
	* cp-tree.h (selftest::run_cp_tests): Move decl to bottom of file.
	(selftest::cp_tree_c_tests): New decl.
	* tree.c: Include "selftest.h".
	(lvalue_kind): Handle VIEW_CONVERT_EXPR location wrapper nodes.
	(selftest::test_lvalue_kind): New function.
	(selftest::cp_tree_c_tests): New function.

gcc/ChangeLog:
	* tree.c (maybe_wrap_with_location): Use VIEW_CONVERT_EXPR for
	STRING_CST.
	(selftest::test_location_wrappers): Add coverage for STRING_CST.
	* tree.h (location_wrapper_p): Update comment to reflect change to
	STRING_CST.
---
 gcc/cp/cp-lang.c |  1 +
 gcc/cp/cp-tree.h | 16 ++++++++------
 gcc/cp/tree.c    | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 gcc/tree.c       | 19 +++++++++++++---
 gcc/tree.h       |  4 ++--
 5 files changed, 95 insertions(+), 11 deletions(-)

OK.

On Thu, Dec 21, 2017 at 12:50 PM, David Malcolm <dmalcolm@redhat.com> wrote:
> On Wed, 2017-12-20 at 23:56 -0500, Jason Merrill wrote:
>> On Wed, Dec 20, 2017 at 5:14 PM, David Malcolm <dmalcolm@redhat.com>
>> wrote:
>> > On Mon, 2017-12-11 at 18:39 -0500, Jason Merrill wrote:
>> > > On 11/10/2017 04:45 PM, David Malcolm wrote:
>> > > > Without this, then lvalue_p returns false for decls, and hence
>> > > > e.g. uses of them for references fail.
>> > > >
>> > > > Stripping location wrappers in lvalue_kind restores the correct
>> > > > behavior of lvalue_p etc.
>> > > >
>> > > > gcc/cp/ChangeLog:
>> > > >     * tree.c (lvalue_kind): Strip any location wrapper.
>> > >
>> > > Rather, lvalue_kind should learn to handle VIEW_CONVERT_EXPR.
>> > This patch does so, using:
>> >
>> >     case NON_LVALUE_EXPR:
>> >     case VIEW_CONVERT_EXPR:
>> >       if (location_wrapper_p (ref))
>> >         return lvalue_kind (TREE_OPERAND (ref, 0));
>> >
>> > As well as the VIEW_CONVERT_EXPR, lvalue_kind needs to handle
>> > NON_LVALUE_EXPR, otherwise a location-wrapped string literal
>> > hits this clause in the "default" case:
>> >
>> >       if (CLASS_TYPE_P (TREE_TYPE (ref))
>> >           || TREE_CODE (TREE_TYPE (ref)) == ARRAY_TYPE)
>> >         return clk_class;
>> >
>> > when it should have hit this one (after removing the
>> > location wrapper):
>> >
>> >     case STRING_CST:
>> >     case COMPOUND_LITERAL_EXPR:
>> >       return clk_ordinary;
>>
>> Ah, the issue is that string literals should use VIEW_CONVERT_EXPR
>> rather than NON_LVALUE_EXPR, since they are lvalues.  With that
>> change, we shouldn't need to handle NON_LVALUE_EXPR specifically.
>>
>> Jason
>
> Thanks.  Here's an updated version of the patch which tweaks
> maybe_wrap_with_location (from patch 02/14 [1]) for STRING_CST to do so,
> also adding some more test coverage to selftest::test_location_wrappers
> for the STRING_CST case.  With that, it only adds the VIEW_CONVERT_EXPR
> case to lvalue_kind.
>
> Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu, as
> part of the kit.
> Manually tested with "make s-selftest-c++" (since we don't run
> the selftests for cc1plus by default).
>
> OK for trunk once the rest of the kit is approved?
>
> [1] https://gcc.gnu.org/ml/gcc-patches/2017-11/msg02611.html
>
> gcc/cp/ChangeLog:
>         * cp-lang.c (selftest::run_cp_tests): Call
>         selftest::cp_tree_c_tests.
>         * cp-tree.h (selftest::run_cp_tests): Move decl to bottom of file.
>         (selftest::cp_tree_c_tests): New decl.
>         * tree.c: Include "selftest.h".
>         (lvalue_kind): Handle VIEW_CONVERT_EXPR location wrapper nodes.
>         (selftest::test_lvalue_kind): New function.
>         (selftest::cp_tree_c_tests): New function.
>
> gcc/ChangeLog:
>         * tree.c (maybe_wrap_with_location): Use VIEW_CONVERT_EXPR for
>         STRING_CST.
>         (selftest::test_location_wrappers): Add coverage for STRING_CST.
>         * tree.h (location_wrapper_p): Update comment to reflect change to
>         STRING_CST.
> ---
>  gcc/cp/cp-lang.c |  1 +
>  gcc/cp/cp-tree.h | 16 ++++++++------
>  gcc/cp/tree.c    | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  gcc/tree.c       | 19 +++++++++++++---
>  gcc/tree.h       |  4 ++--
>  5 files changed, 95 insertions(+), 11 deletions(-)
>
> diff --git a/gcc/cp/cp-lang.c b/gcc/cp/cp-lang.c
> index 805319a..9bb4ce7 100644
> --- a/gcc/cp/cp-lang.c
> +++ b/gcc/cp/cp-lang.c
> @@ -247,6 +247,7 @@ run_cp_tests (void)
>    c_family_tests ();
>
>    /* Additional C++-specific tests.  */
> +  cp_tree_c_tests ();
>  }
>
>  } // namespace selftest
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 9879e16..bb405f2 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -7415,12 +7415,6 @@ extern tree cp_ubsan_maybe_instrument_downcast   (location_t, tree, tree, tree);
>  extern tree cp_ubsan_maybe_instrument_cast_to_vbase (location_t, tree, tree);
>  extern void cp_ubsan_maybe_initialize_vtbl_ptrs (tree);
>
> -#if CHECKING_P
> -namespace selftest {
> -  extern void run_cp_tests (void);
> -} // namespace selftest
> -#endif /* #if CHECKING_P */
> -
>  /* Inline bodies.  */
>
>  inline tree
> @@ -7451,6 +7445,16 @@ named_decl_hash::equal (const value_type existing, compare_type candidate)
>    return candidate == name;
>  }
>
> +#if CHECKING_P
> +namespace selftest {
> +  extern void run_cp_tests (void);
> +
> +  /* Declarations for specific families of tests within cp,
> +     by source file, in alphabetical order.  */
> +  extern void cp_tree_c_tests (void);
> +} // namespace selftest
> +#endif /* #if CHECKING_P */
> +
>  /* -- end of C++ */
>
>  #endif /* ! GCC_CP_TREE_H */
> diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
> index 0ae2eff..6900bc7 100644
> --- a/gcc/cp/tree.c
> +++ b/gcc/cp/tree.c
> @@ -35,6 +35,7 @@ along with GCC; see the file COPYING3.  If not see
>  #include "stringpool.h"
>  #include "attribs.h"
>  #include "flags.h"
> +#include "selftest.h"
>
>  static tree bot_manip (tree *, int *, void *);
>  static tree bot_replace (tree *, int *, void *);
> @@ -240,6 +241,11 @@ lvalue_kind (const_tree ref)
>      case NON_DEPENDENT_EXPR:
>        return lvalue_kind (TREE_OPERAND (ref, 0));
>
> +    case VIEW_CONVERT_EXPR:
> +      if (location_wrapper_p (ref))
> +       return lvalue_kind (TREE_OPERAND (ref, 0));
> +      /* Fallthrough.  */
> +
>      default:
>        if (!TREE_TYPE (ref))
>         return clk_none;
> @@ -5339,4 +5345,64 @@ lang_check_failed (const char* file, int line, const char* function)
>  }
>  #endif /* ENABLE_TREE_CHECKING */
>
> +#if CHECKING_P
> +
> +namespace selftest {
> +
> +/* Verify that lvalue_kind () works, for various expressions,
> +   and that location wrappers don't affect the results.  */
> +
> +static void
> +test_lvalue_kind ()
> +{
> +  location_t loc = BUILTINS_LOCATION;
> +
> +  /* Verify constants and parameters, without and with
> +     location wrappers.  */
> +  tree int_cst = build_int_cst (integer_type_node, 42);
> +  ASSERT_EQ (clk_none, lvalue_kind (integer_zero_node));
> +
> +  tree wrapped_int_cst = maybe_wrap_with_location (int_cst, loc);
> +  ASSERT_TRUE (location_wrapper_p (wrapped_int_cst));
> +  ASSERT_EQ (clk_none, lvalue_kind (integer_zero_node));
> +
> +  tree string_lit = build_string (4, "foo");
> +  TREE_TYPE (string_lit) = char_array_type_node;
> +  string_lit = fix_string_type (string_lit);
> +  ASSERT_EQ (clk_ordinary, lvalue_kind (string_lit));
> +
> +  tree wrapped_string_lit = maybe_wrap_with_location (string_lit, loc);
> +  ASSERT_TRUE (location_wrapper_p (wrapped_string_lit));
> +  ASSERT_EQ (clk_ordinary, lvalue_kind (wrapped_string_lit));
> +
> +  tree parm = build_decl (UNKNOWN_LOCATION, PARM_DECL,
> +                         get_identifier ("some_parm"),
> +                         integer_type_node);
> +  ASSERT_EQ (clk_ordinary, lvalue_kind (parm));
> +
> +  tree wrapped_parm = maybe_wrap_with_location (parm, loc);
> +  ASSERT_TRUE (location_wrapper_p (wrapped_parm));
> +  ASSERT_EQ (clk_ordinary, lvalue_kind (parm));
> +
> +  /* Verify that lvalue_kind of std::move on a parm isn't
> +     affected by location wrappers.  */
> +  tree rvalue_ref_of_parm = move (parm);
> +  ASSERT_EQ (clk_rvalueref, lvalue_kind (rvalue_ref_of_parm));
> +  tree rvalue_ref_of_wrapped_parm = move (wrapped_parm);
> +  ASSERT_EQ (clk_rvalueref, lvalue_kind (rvalue_ref_of_wrapped_parm));
> +}
> +
> +/* Run all of the selftests within this file.  */
> +
> +void
> +cp_tree_c_tests ()
> +{
> +  test_lvalue_kind ();
> +}
> +
> +} // namespace selftest
> +
> +#endif /* #if CHECKING_P */
> +
> +
>  #include "gt-cp-tree.h"
> diff --git a/gcc/tree.c b/gcc/tree.c
> index b72f963..517f4a4 100644
> --- a/gcc/tree.c
> +++ b/gcc/tree.c
> @@ -13811,8 +13811,8 @@ set_source_range (tree expr, source_range src_range)
>  /* Return EXPR, potentially wrapped with a node expression LOC,
>     if !CAN_HAVE_LOCATION_P (expr).
>
> -   NON_LVALUE_EXPR is used for wrapping constants.
> -   VIEW_CONVERT_EXPR is used for wrapping non-constants.
> +   NON_LVALUE_EXPR is used for wrapping constants, apart from STRING_CST.
> +   VIEW_CONVERT_EXPR is used for wrapping non-constants and STRING_CST.
>
>     Wrapper nodes can be identified using location_wrapper_p.  */
>
> @@ -13834,7 +13834,7 @@ maybe_wrap_with_location (tree expr, location_t loc)
>    if (EXCEPTIONAL_CLASS_P (expr))
>      return expr;
>
> -  if (CONSTANT_CLASS_P (expr))
> +  if (CONSTANT_CLASS_P (expr) && TREE_CODE (expr) != STRING_CST)
>      return build1_loc (loc, NON_LVALUE_EXPR, TREE_TYPE (expr), expr);
>    else
>      return build1_loc (loc, VIEW_CONVERT_EXPR, TREE_TYPE (expr), expr);
> @@ -14238,6 +14238,18 @@ test_location_wrappers ()
>    ASSERT_EQ (loc, EXPR_LOCATION (wrapped_int_cst));
>    ASSERT_EQ (int_cst, tree_strip_any_location_wrapper (wrapped_int_cst));
>
> +  /* Wrapping a STRING_CST.  */
> +  tree string_cst = build_string (4, "foo");
> +  ASSERT_FALSE (CAN_HAVE_LOCATION_P (string_cst));
> +  ASSERT_FALSE (location_wrapper_p (string_cst));
> +
> +  tree wrapped_string_cst = maybe_wrap_with_location (string_cst, loc);
> +  ASSERT_TRUE (location_wrapper_p (wrapped_string_cst));
> +  ASSERT_EQ (VIEW_CONVERT_EXPR, TREE_CODE (wrapped_string_cst));
> +  ASSERT_EQ (loc, EXPR_LOCATION (wrapped_string_cst));
> +  ASSERT_EQ (string_cst, tree_strip_any_location_wrapper (wrapped_string_cst));
> +
> +
>    /* Wrapping a variable.  */
>    tree int_var = build_decl (UNKNOWN_LOCATION, VAR_DECL,
>                              get_identifier ("some_int_var"),
> @@ -14258,6 +14270,7 @@ test_location_wrappers ()
>
>    /* Verify that STRIP_NOPS removes wrappers.  */
>    check_strip_nops (wrapped_int_cst, int_cst);
> +  check_strip_nops (wrapped_string_cst, string_cst);
>    check_strip_nops (wrapped_int_var, int_var);
>
>    /* operand_equal_p should "see through" any location wrapper...  */
> diff --git a/gcc/tree.h b/gcc/tree.h
> index de085ca..7f4ea5e 100644
> --- a/gcc/tree.h
> +++ b/gcc/tree.h
> @@ -3679,8 +3679,8 @@ location_wrapper_p (const_tree exp)
>    /* A wrapper node has code NON_LVALUE_EXPR or VIEW_CONVERT_EXPR, and the
>       same type as its operand.
>
> -     NON_LVALUE_EXPR is used for wrapping constants.
> -     VIEW_CONVERT_EXPR is used for wrapping non-constants.
> +     NON_LVALUE_EXPR is used for wrapping constants, apart from STRING_CST.
> +     VIEW_CONVERT_EXPR is used for wrapping non-constants and STRING_CST.
>
>       A subtlety is that we may have to test whether we have the correct
>       TREE_CODE for the wrapped TREE_CODE.  Otherwise, e.g. the C++ expression:
> --
> 1.8.5.3
>