[PATCH] c++: Fix up diagnostics about taking address of an immediate member function [PR102753]
Jason Merrill
jason@redhat.com
Wed Nov 24 22:15:51 GMT 2021
On 11/24/21 13:02, Jakub Jelinek wrote:
> On Wed, Nov 24, 2021 at 05:02:03PM +0100, Jakub Jelinek via Gcc-patches wrote:
>> Unfortunately, the location wrappers are optimized away before we get a
>> chance to use them in cp_fold_r.
>> So, on the following patch, we get the location right on PTRMEM_CSTs not
>> used inside of initializers, but for PTRMEM_CSTs in initializers we report
>> them at UNKNOWN_LOCATION.
>> As PTRMEM_CST is a C++ FE tree, I wonder if we couldn't instead of your
>> patch or in addition to it do:
>> struct GTY(()) ptrmem_cst {
>> struct tree_common common;
>> tree member;
>> + location_t locus;
>> };
>> #define PTRMEM_CST_LOCATION(NODE) \
>> (((ptrmem_cst_t)PTRMEM_CST_CHECK (NODE))->locus)
>> and in make_ptrmem_cst set PTRMEM_CST_LOCATION to input_location.
>
> Here is a full so far lightly tested patch that does this,
> GXX_TESTSUITE_STDS=98,11,14,17,20,2b make check-g++ \
> RUNTESTFLAGS="dg.exp='consteval* srcloc* is-constant-eval* spaceship-synth* constexpr-99287* feat-cxx* lambda-specifiers1*'"
> which covers all tests that use consteval keyword in gcc/testsuite/.
>
> Ok for trunk if it passes full bootstrap/regtest?
>
> 2021-11-24 Jakub Jelinek <jakub@redhat.com>
>
> PR c++/102753
> * cp-tree.h (struct ptrmem_cst): Add locus member.
> (PTRMEM_CST_LOCATION): Define.
> * tree.c (make_ptrmem_cst): Set PTRMEM_CST_LOCATION to input_location.
> * typeck.c (cp_build_addr_expr_1): Don't diagnose taking address of
> immediate functions here. Instead when taking their address make
> sure the returned ADDR_EXPR has EXPR_LOCATION set.
> * pt.c (tsubst_copy): Ensure ADDR_EXPR of immediate function has
> EXPR_LOCATION set.
> * cp-gimplify.c (cp_fold_r): Diagnose taking address of immediate
> functions here. For consteval if don't walk THEN_CLAUSE.
> (cp_genericize_r): Don't assert calls to immediate functions must
> be source_location_current_p, instead only constant evaluate
> calls to source_location_current_p.
>
> * g++.dg/cpp2a/consteval20.C: Add some extra tests.
> * g++.dg/cpp2a/consteval23.C: Likewise.
> * g++.dg/cpp2a/consteval25.C: New test.
> * g++.dg/cpp2a/srcloc20.C: New test.
>
> --- gcc/cp/cp-tree.h.jj 2021-11-24 15:05:23.291928876 +0100
> +++ gcc/cp/cp-tree.h 2021-11-24 17:08:19.507806769 +0100
> @@ -703,6 +703,7 @@ struct GTY(()) template_parm_index {
> struct GTY(()) ptrmem_cst {
> struct tree_common common;
> tree member;
> + location_t locus;
> };
> typedef struct ptrmem_cst * ptrmem_cst_t;
>
> @@ -4724,6 +4725,11 @@ more_aggr_init_expr_args_p (const aggr_i
> #define PTRMEM_CST_MEMBER(NODE) \
> (((ptrmem_cst_t)PTRMEM_CST_CHECK (NODE))->member)
>
> +/* For a pointer-to-member constant `X::Y' this is a location where
> + the address of the member has been taken. */
> +#define PTRMEM_CST_LOCATION(NODE) \
> + (((ptrmem_cst_t)PTRMEM_CST_CHECK (NODE))->locus)
> +
> /* The expression in question for a TYPEOF_TYPE. */
> #define TYPEOF_TYPE_EXPR(NODE) (TYPE_VALUES_RAW (TYPEOF_TYPE_CHECK (NODE)))
>
> --- gcc/cp/tree.c.jj 2021-11-24 15:05:23.371927735 +0100
> +++ gcc/cp/tree.c 2021-11-24 17:09:05.348164621 +0100
> @@ -5167,6 +5167,7 @@ make_ptrmem_cst (tree type, tree member)
> tree ptrmem_cst = make_node (PTRMEM_CST);
> TREE_TYPE (ptrmem_cst) = type;
> PTRMEM_CST_MEMBER (ptrmem_cst) = member;
> + PTRMEM_CST_LOCATION (ptrmem_cst) = input_location;
> return ptrmem_cst;
> }
>
> --- gcc/cp/typeck.c.jj 2021-11-24 09:54:11.521738651 +0100
> +++ gcc/cp/typeck.c 2021-11-24 17:09:43.620628485 +0100
> @@ -6780,16 +6780,6 @@ cp_build_addr_expr_1 (tree arg, bool str
> return error_mark_node;
> }
>
> - if (TREE_CODE (t) == FUNCTION_DECL
> - && DECL_IMMEDIATE_FUNCTION_P (t)
> - && !in_immediate_context ())
> - {
> - if (complain & tf_error)
> - error_at (loc, "taking address of an immediate function %qD",
> - t);
> - return error_mark_node;
> - }
> -
> type = build_ptrmem_type (context_for_name_lookup (t),
> TREE_TYPE (t));
> t = make_ptrmem_cst (type, t);
> @@ -6816,15 +6806,6 @@ cp_build_addr_expr_1 (tree arg, bool str
> {
> tree stripped_arg = tree_strip_any_location_wrapper (arg);
> if (TREE_CODE (stripped_arg) == FUNCTION_DECL
> - && DECL_IMMEDIATE_FUNCTION_P (stripped_arg)
> - && !in_immediate_context ())
> - {
> - if (complain & tf_error)
> - error_at (loc, "taking address of an immediate function %qD",
> - stripped_arg);
> - return error_mark_node;
> - }
> - if (TREE_CODE (stripped_arg) == FUNCTION_DECL
> && !mark_used (stripped_arg, complain) && !(complain & tf_error))
> return error_mark_node;
> val = build_address (arg);
> @@ -6865,6 +6846,13 @@ cp_build_addr_expr_1 (tree arg, bool str
> complain);
> }
>
> + /* For addresses of immediate functions ensure we have EXPR_LOCATION
> + set for possible later diagnostics. */
> + if (TREE_CODE (val) == ADDR_EXPR
> + && TREE_CODE (TREE_OPERAND (val, 0)) == FUNCTION_DECL
> + && DECL_IMMEDIATE_FUNCTION_P (TREE_OPERAND (val, 0)))
> + SET_EXPR_LOCATION (val, input_location);
> +
> return val;
> }
>
> --- gcc/cp/pt.c.jj 2021-11-24 15:05:23.336928234 +0100
> +++ gcc/cp/pt.c 2021-11-24 15:34:29.018014159 +0100
> @@ -17012,6 +17012,12 @@ tsubst_copy (tree t, tree args, tsubst_f
> r = build1 (code, type, op0);
> if (code == ALIGNOF_EXPR)
> ALIGNOF_EXPR_STD_P (r) = ALIGNOF_EXPR_STD_P (t);
> + /* For addresses of immediate functions ensure we have EXPR_LOCATION
> + set for possible later diagnostics. */
> + if (code == ADDR_EXPR
> + && TREE_CODE (op0) == FUNCTION_DECL
> + && DECL_IMMEDIATE_FUNCTION_P (op0))
> + SET_EXPR_LOCATION (r, input_location);
> return r;
> }
>
> --- gcc/cp/cp-gimplify.c.jj 2021-11-19 10:04:54.343314733 +0100
> +++ gcc/cp/cp-gimplify.c 2021-11-24 18:39:46.080233582 +0100
> @@ -900,8 +900,58 @@ struct cp_genericize_data
> static tree
> cp_fold_r (tree *stmt_p, int *walk_subtrees, void *data)
> {
> - tree stmt;
> - enum tree_code code;
> + tree stmt = *stmt_p;
> + enum tree_code code = TREE_CODE (stmt);
> +
> + switch (code)
> + {
> + case PTRMEM_CST:
> + if (TREE_CODE (PTRMEM_CST_MEMBER (stmt)) == FUNCTION_DECL
> + && DECL_IMMEDIATE_FUNCTION_P (PTRMEM_CST_MEMBER (stmt)))
> + {
> + if (!((hash_set<tree> *) data)->add (stmt))
> + error_at (PTRMEM_CST_LOCATION (stmt),
> + "taking address of an immediate function %qD",
> + PTRMEM_CST_MEMBER (stmt));
> + stmt = *stmt_p = build_zero_cst (TREE_TYPE (stmt));
> + break;
> + }
> + break;
> +
> + case ADDR_EXPR:
> + if (TREE_CODE (TREE_OPERAND (stmt, 0)) == FUNCTION_DECL
> + && DECL_IMMEDIATE_FUNCTION_P (TREE_OPERAND (stmt, 0)))
> + {
> + /* Direct calls to std::source_location::current() are
> + only evaluated during genericization, so we need
> + to make an exception for them. But we shouldn't
> + allow those outside of direct calls. */
> + if (source_location_current_p (TREE_OPERAND (stmt, 0))
> + && ((hash_set<tree> *) data)->contains (stmt))
> + break;
> + error_at (EXPR_LOCATION (stmt),
> + "taking address of an immediate function %qD",
> + TREE_OPERAND (stmt, 0));
> + stmt = *stmt_p = build_zero_cst (TREE_TYPE (stmt));
> + break;
> + }
> + break;
> +
> + case CALL_EXPR:
> + if (tree fndecl = cp_get_callee_fndecl_nofold (stmt))
> + if (DECL_IMMEDIATE_FUNCTION_P (fndecl)
> + && source_location_current_p (fndecl))
> + {
> + tree fn = cp_get_callee (stmt);
> + STRIP_NOPS (fn);
> + if (TREE_CODE (fn) == ADDR_EXPR)
> + ((hash_set<tree> *) data)->add (fn);
> + }
> + break;
I'm surprised the source_location::current handling would be needed; why
do calls to that function live long enough for us to walk into the
ADDR_EXPR here? Maybe we should fold it in cp_fold instead of
cp_genericize_r.
> + default:
> + break;
> + }
>
> *stmt_p = stmt = cp_fold (*stmt_p);
>
> @@ -917,12 +967,16 @@ cp_fold_r (tree *stmt_p, int *walk_subtr
> }
>
> code = TREE_CODE (stmt);
> - if (code == OMP_FOR || code == OMP_SIMD || code == OMP_DISTRIBUTE
> - || code == OMP_LOOP || code == OMP_TASKLOOP || code == OACC_LOOP)
> + switch (code)
> {
> tree x;
> int i, n;
> -
> + case OMP_FOR:
> + case OMP_SIMD:
> + case OMP_DISTRIBUTE:
> + case OMP_LOOP:
> + case OMP_TASKLOOP:
> + case OACC_LOOP:
> cp_walk_tree (&OMP_FOR_BODY (stmt), cp_fold_r, data, NULL);
> cp_walk_tree (&OMP_FOR_CLAUSES (stmt), cp_fold_r, data, NULL);
> cp_walk_tree (&OMP_FOR_INIT (stmt), cp_fold_r, data, NULL);
> @@ -961,6 +1015,22 @@ cp_fold_r (tree *stmt_p, int *walk_subtr
> }
> cp_walk_tree (&OMP_FOR_PRE_BODY (stmt), cp_fold_r, data, NULL);
> *walk_subtrees = 0;
> + return NULL;
> +
> + case IF_STMT:
> + if (IF_STMT_CONSTEVAL_P (stmt))
> + {
> + /* Don't walk THEN_CLAUSE (stmt) for consteval if. IF_COND is always
> + boolean_false_node. */
> + cp_walk_tree (&ELSE_CLAUSE (stmt), cp_fold_r, data, NULL);
> + cp_walk_tree (&IF_SCOPE (stmt), cp_fold_r, data, NULL);
> + *walk_subtrees = 0;
> + return NULL;
> + }
> + break;
> +
> + default:
> + break;
> }
>
> return NULL;
> @@ -1477,9 +1547,9 @@ cp_genericize_r (tree *stmt_p, int *walk
> }
>
> if (tree fndecl = cp_get_callee_fndecl_nofold (stmt))
> - if (DECL_IMMEDIATE_FUNCTION_P (fndecl))
> + if (DECL_IMMEDIATE_FUNCTION_P (fndecl)
> + && source_location_current_p (fndecl))
> {
> - gcc_assert (source_location_current_p (fndecl));
> *stmt_p = cxx_constant_value (stmt);
> break;
> }
> --- gcc/testsuite/g++.dg/cpp2a/consteval20.C.jj 2021-10-27 09:03:07.576043195 +0200
> +++ gcc/testsuite/g++.dg/cpp2a/consteval20.C 2021-11-24 16:49:40.481679281 +0100
> @@ -10,10 +10,14 @@ constexpr S s;
> int
> bar ()
> {
> + auto c = &S::foo; // { dg-error "taking address of an immediate function" }
> + constexpr auto d = &S::foo; // { dg-error "taking address of an immediate function" }
> + static auto e = &S::foo; // { dg-error "taking address of an immediate function" }
> return (s.*&S::foo) (); // { dg-error "taking address of an immediate function" }
> }
>
> constexpr auto a = &S::foo; // { dg-error "taking address of an immediate function" }
> +auto b = &S::foo; // { dg-error "taking address of an immediate function" }
>
> consteval int
> baz ()
> --- gcc/testsuite/g++.dg/cpp2a/consteval23.C.jj 2021-10-27 09:03:07.576043195 +0200
> +++ gcc/testsuite/g++.dg/cpp2a/consteval23.C 2021-11-24 18:49:34.721877913 +0100
> @@ -2,6 +2,7 @@
> // { dg-do compile { target c++20 } }
>
> consteval int foo () { return 42; }
> +constexpr auto baz (int (*fn) ()) { return fn; }
>
> consteval int
> bar (int (*fn) () = foo)
> @@ -11,3 +12,6 @@ bar (int (*fn) () = foo)
>
> static_assert (bar () == 42);
> static_assert (bar (foo) == 42);
> +static_assert (bar (&foo) == 42);
> +static_assert (bar (baz (foo)) == 42);
> +static_assert (bar (baz (&foo)) == 42);
> --- gcc/testsuite/g++.dg/cpp2a/consteval25.C.jj 2021-11-24 18:49:28.321968743 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/consteval25.C 2021-11-24 18:50:41.790926102 +0100
> @@ -0,0 +1,17 @@
> +// PR c++/102753
> +// { dg-do compile { target c++20 } }
> +// { dg-options "" }
> +
> +consteval int foo () { return 42; }
> +
> +consteval int
> +bar (int (*fn) ())
> +{
> + return fn ();
> +}
> +
> +void
> +baz ()
> +{
> + static_assert (bar (({ constexpr auto a = 1; foo; })) == 42);
> +}
> --- gcc/testsuite/g++.dg/cpp2a/srcloc20.C.jj 2021-11-24 18:45:35.810268971 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/srcloc20.C 2021-11-24 18:48:01.280204003 +0100
> @@ -0,0 +1,44 @@
> +// { dg-do compile { target c++20 } }
> +
> +namespace std {
> + struct source_location {
> + struct __impl {
> + const char *_M_file_name;
> + const char *_M_function_name;
> + unsigned int _M_line, _M_column;
> + };
> + const __impl *__ptr;
> + constexpr source_location () : __ptr (nullptr) {}
> + static consteval source_location
> + current (const void *__p = __builtin_source_location ()) {
> + source_location __ret;
> + __ret.__ptr = static_cast <const __impl *> (__p);
> + return __ret;
> + }
> + constexpr const char *file_name () const {
> + return __ptr ? __ptr->_M_file_name : "";
> + }
> + constexpr const char *function_name () const {
> + return __ptr ? __ptr->_M_function_name : "";
> + }
> + constexpr unsigned line () const {
> + return __ptr ? __ptr->_M_line : 0;
> + }
> + constexpr unsigned column () const {
> + return __ptr ? __ptr->_M_column : 0;
> + }
> + };
> +}
> +
> +using namespace std;
> +
> +auto a = source_location::current; // { dg-error "taking address of an immediate function" }
> +constexpr auto b = &source_location::current; // { dg-error "taking address of an immediate function" }
> +
> +void
> +foo ()
> +{
> + auto c = &source_location::current; // { dg-error "taking address of an immediate function" }
> + constexpr auto d = source_location::current; // { dg-error "taking address of an immediate function" }
> + static auto e = source_location::current; // { dg-error "taking address of an immediate function" }
> +}
>
>
> Jakub
>
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