* [PATCH] c++: Fix up constexpr evaluation of new with zero sized types [PR104568]
@ 2022-02-21 8:25 Jakub Jelinek
2022-03-12 4:28 ` Jason Merrill
0 siblings, 1 reply; 6+ messages in thread
From: Jakub Jelinek @ 2022-02-21 8:25 UTC (permalink / raw)
To: Jason Merrill; +Cc: gcc-patches
Hi!
The new expression constant expression evaluation right now tries to
deduce how many elts the array it uses for the heap or heap [] vars
should have (or how many elts should its trailing array have if it has
cookie at the start). As new is lowered at that point to
(some_type *) ::operator new (size)
or so, it computes it by subtracting cookie size if any from size, then
divides the result by sizeof (some_type).
This works fine for most types, except when sizeof (some_type) is 0,
then we divide by zero; size is then equal to cookie_size (or if there
is no cookie, to 0).
The following patch special cases those cases so that we don't divide
by zero and also recover the original outer_nelts from the expression
by forcing the size not to be folded in that case but be explicit
0 * outer_nelts or cookie_size + 0 * outer_nelts.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Note, we have further issues, we accept-invalid various cases, for both
zero sized elt_type and even non-zero sized elts, we aren't able to
diagnose out of bounds POINTER_PLUS_EXPR like:
constexpr bool
foo ()
{
auto p = new int[2];
auto q1 = &p[0];
auto q2 = &p[1];
auto q3 = &p[2];
auto q4 = &p[3];
delete[] p;
return true;
}
constexpr bool a = foo ();
That doesn't look like a regression so I think we should resolve that for
GCC 13, but there are 2 problems. Figure out why
cxx_fold_pointer_plus_expression doesn't deal with the &heap []
etc. cases, and for the zero sized arrays, I think we really need to preserve
whether user wrote an array ref or pointer addition, because in the
&p[3] case if sizeof(p[0]) == 0 we know that if it has 2 elements it is
out of bounds, while if we see p p+ 0 the information if it was
p + 2 or p + 3 in the source is lost.
clang++ seems to handle it fine even in the zero sized cases or with
new expressions.
2022-02-21 Jakub Jelinek <jakub@redhat.com>
PR c++/104568
* cp-tree.h (build_new_constexpr_heap_type): Add FULL_SIZE_ADJUSTED
argument.
* init.cc (build_new_constexpr_heap_type): Add FULL_SIZE_ADJUSTED
argument. If true, don't subtract csz from it nor divide by
int_size_in_bytes (elt_type). Don't do that division if
int_size_in_bytes is zero either.
(maybe_wrap_new_for_constexpr): Pass false to
build_new_constexpr_heap_type.
(build_new_1): If size is 0, change it to 0 * outer_nelts if
outer_nelts is non-NULL. Pass type rather than elt_type to
maybe_wrap_new_for_constexpr.
* constexpr.cc (cxx_eval_constant_expression) <case CONVERT_EXPR>:
If elt_size is zero sized type, try to recover outer_nelts from
the size argument to operator new/new[] and pass that as
var_size to build_new_constexpr_heap_type together with true
for the last argument.
* g++.dg/cpp2a/constexpr-new22.C: New test.
--- gcc/cp/cp-tree.h.jj 2022-02-09 20:13:51.541304861 +0100
+++ gcc/cp/cp-tree.h 2022-02-17 15:34:30.804453673 +0100
@@ -7038,7 +7038,7 @@ extern tree build_offset_ref (tree, tr
extern tree throw_bad_array_new_length (void);
extern bool type_has_new_extended_alignment (tree);
extern unsigned malloc_alignment (void);
-extern tree build_new_constexpr_heap_type (tree, tree, tree);
+extern tree build_new_constexpr_heap_type (tree, tree, tree, bool);
extern tree build_new (location_t,
vec<tree, va_gc> **, tree,
tree, vec<tree, va_gc> **,
--- gcc/cp/init.cc.jj 2022-02-05 10:50:05.000000000 +0100
+++ gcc/cp/init.cc 2022-02-17 15:56:30.010056499 +0100
@@ -2930,7 +2930,8 @@ std_placement_new_fn_p (tree alloc_fn)
it is computed such that the size of the struct fits into FULL_SIZE. */
tree
-build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree full_size)
+build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree full_size,
+ bool full_size_adjusted)
{
gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size));
gcc_assert (full_size == NULL_TREE || tree_fits_uhwi_p (full_size));
@@ -2939,9 +2940,14 @@ build_new_constexpr_heap_type (tree elt_
if (full_size)
{
unsigned HOST_WIDE_INT fsz = tree_to_uhwi (full_size);
- gcc_assert (fsz >= csz);
- fsz -= csz;
- fsz /= int_size_in_bytes (elt_type);
+ unsigned HOST_WIDE_INT esz = int_size_in_bytes (elt_type);
+ if (!full_size_adjusted)
+ {
+ gcc_assert (fsz >= csz);
+ fsz -= csz;
+ if (esz)
+ fsz /= esz;
+ }
itype2 = build_index_type (size_int (fsz - 1));
if (!cookie_size)
return build_cplus_array_type (elt_type, itype2);
@@ -2992,7 +2998,7 @@ maybe_wrap_new_for_constexpr (tree alloc
return alloc_call;
tree rtype = build_new_constexpr_heap_type (elt_type, cookie_size,
- NULL_TREE);
+ NULL_TREE, false);
return build_nop (build_pointer_type (rtype), alloc_call);
}
@@ -3398,6 +3404,12 @@ build_new_1 (vec<tree, va_gc> **placemen
outer_nelts_check = NULL_TREE;
}
+ /* If size is zero e.g. due to type having zero size, try to
+ preserve outer_nelts for constant expression evaluation
+ purposes. */
+ if (integer_zerop (size) && outer_nelts)
+ size = build2 (MULT_EXPR, TREE_TYPE (size), size, outer_nelts);
+
alloc_call = build_operator_new_call (fnname, placement,
&size, &cookie_size,
align_arg, outer_nelts_check,
@@ -3474,7 +3486,7 @@ build_new_1 (vec<tree, va_gc> **placemen
}
if (cookie_size)
- alloc_call = maybe_wrap_new_for_constexpr (alloc_call, elt_type,
+ alloc_call = maybe_wrap_new_for_constexpr (alloc_call, type,
cookie_size);
/* In the simple case, we can stop now. */
--- gcc/cp/constexpr.cc.jj 2022-02-17 10:24:16.779112954 +0100
+++ gcc/cp/constexpr.cc 2022-02-17 15:43:23.399026306 +0100
@@ -7253,6 +7253,7 @@ cxx_eval_constant_expression (const cons
tree var_size = TYPE_SIZE_UNIT (TREE_TYPE (var));
tree elt_type = TREE_TYPE (type);
tree cookie_size = NULL_TREE;
+ bool var_size_adjusted = false;
if (TREE_CODE (elt_type) == RECORD_TYPE
&& TYPE_NAME (elt_type) == heap_identifier)
{
@@ -7264,9 +7265,66 @@ cxx_eval_constant_expression (const cons
DECL_NAME (var)
= (DECL_NAME (var) == heap_uninit_identifier
? heap_identifier : heap_vec_identifier);
+ /* For zero sized elt_type, try to recover how many outer_nelts
+ it should have. */
+ if ((cookie_size ? tree_int_cst_equal (var_size, cookie_size)
+ : integer_zerop (var_size))
+ && !int_size_in_bytes (elt_type)
+ && TREE_CODE (oldop) == CALL_EXPR
+ && call_expr_nargs (oldop) >= 1)
+ if (tree fun = get_function_named_in_call (oldop))
+ if (cxx_replaceable_global_alloc_fn (fun)
+ && IDENTIFIER_NEW_OP_P (DECL_NAME (fun)))
+ {
+ tree arg0 = CALL_EXPR_ARG (oldop, 0);
+ STRIP_NOPS (arg0);
+ if (cookie_size)
+ {
+ if (TREE_CODE (arg0) != PLUS_EXPR)
+ arg0 = NULL_TREE;
+ else if (TREE_CODE (TREE_OPERAND (arg0, 0))
+ == INTEGER_CST
+ && tree_int_cst_equal (cookie_size,
+ TREE_OPERAND (arg0,
+ 0)))
+ {
+ arg0 = TREE_OPERAND (arg0, 1);
+ STRIP_NOPS (arg0);
+ }
+ else if (TREE_CODE (TREE_OPERAND (arg0, 1))
+ == INTEGER_CST
+ && tree_int_cst_equal (cookie_size,
+ TREE_OPERAND (arg0,
+ 1)))
+ {
+ arg0 = TREE_OPERAND (arg0, 0);
+ STRIP_NOPS (arg0);
+ }
+ else
+ arg0 = NULL_TREE;
+ }
+ if (arg0 && TREE_CODE (arg0) == MULT_EXPR)
+ {
+ tree op0 = TREE_OPERAND (arg0, 0);
+ tree op1 = TREE_OPERAND (arg0, 1);
+ var_size_adjusted = true;
+ if (integer_zerop (op0))
+ var_size
+ = cxx_eval_constant_expression (ctx, op1, false,
+ non_constant_p,
+ overflow_p);
+ else if (integer_zerop (op1))
+ var_size
+ = cxx_eval_constant_expression (ctx, op0, false,
+ non_constant_p,
+ overflow_p);
+ else
+ var_size_adjusted = false;
+ }
+ }
TREE_TYPE (var)
= build_new_constexpr_heap_type (elt_type, cookie_size,
- var_size);
+ var_size, var_size_adjusted);
TREE_TYPE (TREE_OPERAND (op, 0))
= build_pointer_type (TREE_TYPE (var));
}
--- gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C.jj 2022-02-17 16:01:24.804945381 +0100
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C 2022-02-17 16:00:55.720350985 +0100
@@ -0,0 +1,42 @@
+// PR c++/104568
+// { dg-do compile { target c++20 } }
+// { dg-options "" }
+
+struct S { int s; constexpr S () : s (0) {} constexpr ~S () {} };
+typedef int T[0];
+typedef int U[0];
+
+constexpr bool
+foo ()
+{
+ auto p = new T[2];
+ auto q1 = &p[0];
+ auto q2 = &p[1];
+ auto q3 = &p[2];
+ delete[] p;
+ return true;
+}
+
+constexpr bool
+bar ()
+{
+ auto p = new U[2];
+ auto q1 = &p[0];
+ auto q2 = &p[1];
+ auto q3 = &p[2];
+ delete[] p;
+ return true;
+}
+
+constexpr bool
+baz ()
+{
+ auto p = new T[0];
+ auto q1 = &p[0];
+ delete[] p;
+ return true;
+}
+
+constexpr bool a = foo ();
+constexpr bool b = bar ();
+constexpr bool c = baz ();
Jakub
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] c++: Fix up constexpr evaluation of new with zero sized types [PR104568]
2022-02-21 8:25 [PATCH] c++: Fix up constexpr evaluation of new with zero sized types [PR104568] Jakub Jelinek
@ 2022-03-12 4:28 ` Jason Merrill
2022-03-15 11:44 ` Jakub Jelinek
0 siblings, 1 reply; 6+ messages in thread
From: Jason Merrill @ 2022-03-12 4:28 UTC (permalink / raw)
To: Jakub Jelinek; +Cc: gcc-patches
On 2/21/22 04:25, Jakub Jelinek wrote:
> Hi!
>
> The new expression constant expression evaluation right now tries to
> deduce how many elts the array it uses for the heap or heap [] vars
> should have (or how many elts should its trailing array have if it has
> cookie at the start). As new is lowered at that point to
> (some_type *) ::operator new (size)
> or so, it computes it by subtracting cookie size if any from size, then
> divides the result by sizeof (some_type).
> This works fine for most types, except when sizeof (some_type) is 0,
> then we divide by zero; size is then equal to cookie_size (or if there
> is no cookie, to 0).
> The following patch special cases those cases so that we don't divide
> by zero and also recover the original outer_nelts from the expression
> by forcing the size not to be folded in that case but be explicit
> 0 * outer_nelts or cookie_size + 0 * outer_nelts.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> Note, we have further issues, we accept-invalid various cases, for both
> zero sized elt_type and even non-zero sized elts, we aren't able to
> diagnose out of bounds POINTER_PLUS_EXPR like:
> constexpr bool
> foo ()
> {
> auto p = new int[2];
> auto q1 = &p[0];
> auto q2 = &p[1];
> auto q3 = &p[2];
> auto q4 = &p[3];
> delete[] p;
> return true;
> }
> constexpr bool a = foo ();
> That doesn't look like a regression so I think we should resolve that for
> GCC 13, but there are 2 problems. Figure out why
> cxx_fold_pointer_plus_expression doesn't deal with the &heap []
> etc. cases, and for the zero sized arrays, I think we really need to preserve
> whether user wrote an array ref or pointer addition, because in the
> &p[3] case if sizeof(p[0]) == 0 we know that if it has 2 elements it is
> out of bounds, while if we see p p+ 0 the information if it was
> p + 2 or p + 3 in the source is lost.
But array ref is defined to be equivalent to pointer addition, and we
also want to handle p+2 properly. It seems to me that the problem is
lowering to POINTER_PLUS_EXPR too soon, but that's definitely a stage 1
project.
> clang++ seems to handle it fine even in the zero sized cases or with
> new expressions.
>
> 2022-02-21 Jakub Jelinek <jakub@redhat.com>
>
> PR c++/104568
> * cp-tree.h (build_new_constexpr_heap_type): Add FULL_SIZE_ADJUSTED
> argument.
> * init.cc (build_new_constexpr_heap_type): Add FULL_SIZE_ADJUSTED
> argument. If true, don't subtract csz from it nor divide by
> int_size_in_bytes (elt_type). Don't do that division if
> int_size_in_bytes is zero either.
> (maybe_wrap_new_for_constexpr): Pass false to
> build_new_constexpr_heap_type.
> (build_new_1): If size is 0, change it to 0 * outer_nelts if
> outer_nelts is non-NULL. Pass type rather than elt_type to
> maybe_wrap_new_for_constexpr.
> * constexpr.cc (cxx_eval_constant_expression) <case CONVERT_EXPR>:
> If elt_size is zero sized type, try to recover outer_nelts from
> the size argument to operator new/new[] and pass that as
> var_size to build_new_constexpr_heap_type together with true
> for the last argument.
>
> * g++.dg/cpp2a/constexpr-new22.C: New test.
>
> --- gcc/cp/cp-tree.h.jj 2022-02-09 20:13:51.541304861 +0100
> +++ gcc/cp/cp-tree.h 2022-02-17 15:34:30.804453673 +0100
> @@ -7038,7 +7038,7 @@ extern tree build_offset_ref (tree, tr
> extern tree throw_bad_array_new_length (void);
> extern bool type_has_new_extended_alignment (tree);
> extern unsigned malloc_alignment (void);
> -extern tree build_new_constexpr_heap_type (tree, tree, tree);
> +extern tree build_new_constexpr_heap_type (tree, tree, tree, bool);
> extern tree build_new (location_t,
> vec<tree, va_gc> **, tree,
> tree, vec<tree, va_gc> **,
> --- gcc/cp/init.cc.jj 2022-02-05 10:50:05.000000000 +0100
> +++ gcc/cp/init.cc 2022-02-17 15:56:30.010056499 +0100
> @@ -2930,7 +2930,8 @@ std_placement_new_fn_p (tree alloc_fn)
> it is computed such that the size of the struct fits into FULL_SIZE. */
>
> tree
> -build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree full_size)
> +build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree full_size,
> + bool full_size_adjusted)
> {
> gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size));
> gcc_assert (full_size == NULL_TREE || tree_fits_uhwi_p (full_size));
> @@ -2939,9 +2940,14 @@ build_new_constexpr_heap_type (tree elt_
> if (full_size)
> {
> unsigned HOST_WIDE_INT fsz = tree_to_uhwi (full_size);
> - gcc_assert (fsz >= csz);
> - fsz -= csz;
> - fsz /= int_size_in_bytes (elt_type);
> + unsigned HOST_WIDE_INT esz = int_size_in_bytes (elt_type);
> + if (!full_size_adjusted)
> + {
> + gcc_assert (fsz >= csz);
> + fsz -= csz;
> + if (esz)
> + fsz /= esz;
> + }
> itype2 = build_index_type (size_int (fsz - 1));
> if (!cookie_size)
> return build_cplus_array_type (elt_type, itype2);
> @@ -2992,7 +2998,7 @@ maybe_wrap_new_for_constexpr (tree alloc
> return alloc_call;
>
> tree rtype = build_new_constexpr_heap_type (elt_type, cookie_size,
> - NULL_TREE);
> + NULL_TREE, false);
> return build_nop (build_pointer_type (rtype), alloc_call);
> }
>
> @@ -3398,6 +3404,12 @@ build_new_1 (vec<tree, va_gc> **placemen
> outer_nelts_check = NULL_TREE;
> }
>
> + /* If size is zero e.g. due to type having zero size, try to
> + preserve outer_nelts for constant expression evaluation
> + purposes. */
> + if (integer_zerop (size) && outer_nelts)
> + size = build2 (MULT_EXPR, TREE_TYPE (size), size, outer_nelts);
> +
> alloc_call = build_operator_new_call (fnname, placement,
> &size, &cookie_size,
> align_arg, outer_nelts_check,
> @@ -3474,7 +3486,7 @@ build_new_1 (vec<tree, va_gc> **placemen
> }
>
> if (cookie_size)
> - alloc_call = maybe_wrap_new_for_constexpr (alloc_call, elt_type,
> + alloc_call = maybe_wrap_new_for_constexpr (alloc_call, type,
> cookie_size);
>
> /* In the simple case, we can stop now. */
> --- gcc/cp/constexpr.cc.jj 2022-02-17 10:24:16.779112954 +0100
> +++ gcc/cp/constexpr.cc 2022-02-17 15:43:23.399026306 +0100
> @@ -7253,6 +7253,7 @@ cxx_eval_constant_expression (const cons
> tree var_size = TYPE_SIZE_UNIT (TREE_TYPE (var));
> tree elt_type = TREE_TYPE (type);
> tree cookie_size = NULL_TREE;
> + bool var_size_adjusted = false;
> if (TREE_CODE (elt_type) == RECORD_TYPE
> && TYPE_NAME (elt_type) == heap_identifier)
> {
> @@ -7264,9 +7265,66 @@ cxx_eval_constant_expression (const cons
> DECL_NAME (var)
> = (DECL_NAME (var) == heap_uninit_identifier
> ? heap_identifier : heap_vec_identifier);
> + /* For zero sized elt_type, try to recover how many outer_nelts
> + it should have. */
> + if ((cookie_size ? tree_int_cst_equal (var_size, cookie_size)
> + : integer_zerop (var_size))
> + && !int_size_in_bytes (elt_type)
> + && TREE_CODE (oldop) == CALL_EXPR
> + && call_expr_nargs (oldop) >= 1)
> + if (tree fun = get_function_named_in_call (oldop))
> + if (cxx_replaceable_global_alloc_fn (fun)
> + && IDENTIFIER_NEW_OP_P (DECL_NAME (fun)))
> + {
> + tree arg0 = CALL_EXPR_ARG (oldop, 0);
How about setting var_size to arg0 at this point, and moving the
decomposition of the size expression into build_new_constexpr_heap_type?
> + STRIP_NOPS (arg0);
> + if (cookie_size)
> + {
> + if (TREE_CODE (arg0) != PLUS_EXPR)
> + arg0 = NULL_TREE;
> + else if (TREE_CODE (TREE_OPERAND (arg0, 0))
> + == INTEGER_CST
> + && tree_int_cst_equal (cookie_size,
> + TREE_OPERAND (arg0,
> + 0)))
> + {
> + arg0 = TREE_OPERAND (arg0, 1);
> + STRIP_NOPS (arg0);
> + }
> + else if (TREE_CODE (TREE_OPERAND (arg0, 1))
> + == INTEGER_CST
> + && tree_int_cst_equal (cookie_size,
> + TREE_OPERAND (arg0,
> + 1)))
> + {
> + arg0 = TREE_OPERAND (arg0, 0);
> + STRIP_NOPS (arg0);
> + }
> + else
> + arg0 = NULL_TREE;
> + }
> + if (arg0 && TREE_CODE (arg0) == MULT_EXPR)
> + {
> + tree op0 = TREE_OPERAND (arg0, 0);
> + tree op1 = TREE_OPERAND (arg0, 1);
> + var_size_adjusted = true;
> + if (integer_zerop (op0))
> + var_size
> + = cxx_eval_constant_expression (ctx, op1, false,
> + non_constant_p,
> + overflow_p);
> + else if (integer_zerop (op1))
> + var_size
> + = cxx_eval_constant_expression (ctx, op0, false,
> + non_constant_p,
> + overflow_p);
> + else
> + var_size_adjusted = false;
> + }
> + }
> TREE_TYPE (var)
> = build_new_constexpr_heap_type (elt_type, cookie_size,
> - var_size);
> + var_size, var_size_adjusted);
> TREE_TYPE (TREE_OPERAND (op, 0))
> = build_pointer_type (TREE_TYPE (var));
> }
> --- gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C.jj 2022-02-17 16:01:24.804945381 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C 2022-02-17 16:00:55.720350985 +0100
> @@ -0,0 +1,42 @@
> +// PR c++/104568
> +// { dg-do compile { target c++20 } }
> +// { dg-options "" }
> +
> +struct S { int s; constexpr S () : s (0) {} constexpr ~S () {} };
> +typedef int T[0];
> +typedef int U[0];
> +
> +constexpr bool
> +foo ()
> +{
> + auto p = new T[2];
> + auto q1 = &p[0];
> + auto q2 = &p[1];
> + auto q3 = &p[2];
> + delete[] p;
> + return true;
> +}
> +
> +constexpr bool
> +bar ()
> +{
> + auto p = new U[2];
> + auto q1 = &p[0];
> + auto q2 = &p[1];
> + auto q3 = &p[2];
> + delete[] p;
> + return true;
> +}
> +
> +constexpr bool
> +baz ()
> +{
> + auto p = new T[0];
> + auto q1 = &p[0];
> + delete[] p;
> + return true;
> +}
> +
> +constexpr bool a = foo ();
> +constexpr bool b = bar ();
> +constexpr bool c = baz ();
>
> Jakub
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] c++: Fix up constexpr evaluation of new with zero sized types [PR104568]
2022-03-12 4:28 ` Jason Merrill
@ 2022-03-15 11:44 ` Jakub Jelinek
2022-03-15 20:19 ` Jason Merrill
0 siblings, 1 reply; 6+ messages in thread
From: Jakub Jelinek @ 2022-03-15 11:44 UTC (permalink / raw)
To: Jason Merrill; +Cc: gcc-patches
On Fri, Mar 11, 2022 at 11:28:09PM -0500, Jason Merrill wrote:
> > @@ -7264,9 +7265,66 @@ cxx_eval_constant_expression (const cons
> > DECL_NAME (var)
> > = (DECL_NAME (var) == heap_uninit_identifier
> > ? heap_identifier : heap_vec_identifier);
> > + /* For zero sized elt_type, try to recover how many outer_nelts
> > + it should have. */
> > + if ((cookie_size ? tree_int_cst_equal (var_size, cookie_size)
> > + : integer_zerop (var_size))
> > + && !int_size_in_bytes (elt_type)
> > + && TREE_CODE (oldop) == CALL_EXPR
> > + && call_expr_nargs (oldop) >= 1)
> > + if (tree fun = get_function_named_in_call (oldop))
> > + if (cxx_replaceable_global_alloc_fn (fun)
> > + && IDENTIFIER_NEW_OP_P (DECL_NAME (fun)))
> > + {
> > + tree arg0 = CALL_EXPR_ARG (oldop, 0);
>
> How about setting var_size to arg0 at this point, and moving the
> decomposition of the size expression into build_new_constexpr_heap_type?
That would be more difficult, because for the cxx_eval_constant_expression
calls we need ctx, non_constant_p and overflow_p arguments, so
build_new_constexpr_heap_type would need to remove that one bool arg
added by this patch but instead pass around those 3 new ones.
As build_new_constexpr_heap_type is called only from 2 spots where the
other one passes NULL as full_size, the decomposition is only useful
for this caller and not the other one.
But if you strongly prefer it that way, I can do that.
Note, probably not 3 new args but 4, depends on whether we could turn
all those cases where the tree arg0 = CALL_EXPR_ARG (oldop, 0);
is done but var_size_adjusted is false into assertion failures.
I'm worried that with the zero size of element we could end up with
a variable number of elements which when multiplied by 0 gives constant 0,
though hopefully that would be rejected earlier during constant evaluation.
>
> > + STRIP_NOPS (arg0);
> > + if (cookie_size)
> > + {
> > + if (TREE_CODE (arg0) != PLUS_EXPR)
> > + arg0 = NULL_TREE;
> > + else if (TREE_CODE (TREE_OPERAND (arg0, 0))
> > + == INTEGER_CST
> > + && tree_int_cst_equal (cookie_size,
> > + TREE_OPERAND (arg0,
> > + 0)))
> > + {
> > + arg0 = TREE_OPERAND (arg0, 1);
> > + STRIP_NOPS (arg0);
> > + }
> > + else if (TREE_CODE (TREE_OPERAND (arg0, 1))
> > + == INTEGER_CST
> > + && tree_int_cst_equal (cookie_size,
> > + TREE_OPERAND (arg0,
> > + 1)))
> > + {
> > + arg0 = TREE_OPERAND (arg0, 0);
> > + STRIP_NOPS (arg0);
> > + }
> > + else
> > + arg0 = NULL_TREE;
> > + }
> > + if (arg0 && TREE_CODE (arg0) == MULT_EXPR)
> > + {
> > + tree op0 = TREE_OPERAND (arg0, 0);
> > + tree op1 = TREE_OPERAND (arg0, 1);
> > + var_size_adjusted = true;
> > + if (integer_zerop (op0))
> > + var_size
> > + = cxx_eval_constant_expression (ctx, op1, false,
> > + non_constant_p,
> > + overflow_p);
> > + else if (integer_zerop (op1))
> > + var_size
> > + = cxx_eval_constant_expression (ctx, op0, false,
> > + non_constant_p,
> > + overflow_p);
> > + else
> > + var_size_adjusted = false;
> > + }
> > + }
> > TREE_TYPE (var)
> > = build_new_constexpr_heap_type (elt_type, cookie_size,
> > - var_size);
> > + var_size, var_size_adjusted);
> > TREE_TYPE (TREE_OPERAND (op, 0))
> > = build_pointer_type (TREE_TYPE (var));
> > }
Jakub
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] c++: Fix up constexpr evaluation of new with zero sized types [PR104568]
2022-03-15 11:44 ` Jakub Jelinek
@ 2022-03-15 20:19 ` Jason Merrill
2022-03-16 16:55 ` [PATCH] c++, v2: " Jakub Jelinek
0 siblings, 1 reply; 6+ messages in thread
From: Jason Merrill @ 2022-03-15 20:19 UTC (permalink / raw)
To: Jakub Jelinek; +Cc: gcc-patches
On 3/15/22 07:44, Jakub Jelinek wrote:
> On Fri, Mar 11, 2022 at 11:28:09PM -0500, Jason Merrill wrote:
>>> @@ -7264,9 +7265,66 @@ cxx_eval_constant_expression (const cons
>>> DECL_NAME (var)
>>> = (DECL_NAME (var) == heap_uninit_identifier
>>> ? heap_identifier : heap_vec_identifier);
>>> + /* For zero sized elt_type, try to recover how many outer_nelts
>>> + it should have. */
>>> + if ((cookie_size ? tree_int_cst_equal (var_size, cookie_size)
>>> + : integer_zerop (var_size))
>>> + && !int_size_in_bytes (elt_type)
>>> + && TREE_CODE (oldop) == CALL_EXPR
>>> + && call_expr_nargs (oldop) >= 1)
>>> + if (tree fun = get_function_named_in_call (oldop))
>>> + if (cxx_replaceable_global_alloc_fn (fun)
>>> + && IDENTIFIER_NEW_OP_P (DECL_NAME (fun)))
>>> + {
>>> + tree arg0 = CALL_EXPR_ARG (oldop, 0);
>>
>> How about setting var_size to arg0 at this point, and moving the
>> decomposition of the size expression into build_new_constexpr_heap_type?
>
> That would be more difficult, because for the cxx_eval_constant_expression
> calls we need ctx, non_constant_p and overflow_p arguments, so
> build_new_constexpr_heap_type would need to remove that one bool arg
> added by this patch but instead pass around those 3 new ones.
> As build_new_constexpr_heap_type is called only from 2 spots where the
> other one passes NULL as full_size, the decomposition is only useful
> for this caller and not the other one.
>
> But if you strongly prefer it that way, I can do that.
> Note, probably not 3 new args but 4, depends on whether we could turn
> all those cases where the tree arg0 = CALL_EXPR_ARG (oldop, 0);
> is done but var_size_adjusted is false into assertion failures.
> I'm worried that with the zero size of element we could end up with
> a variable number of elements which when multiplied by 0 gives constant 0,
> though hopefully that would be rejected earlier during constant evaluation.
Or we could move all the adjustment into a separate function and only
ever pass the number of elements to build_new_constexpr_heap_type?
>>> + STRIP_NOPS (arg0);
>>> + if (cookie_size)
>>> + {
>>> + if (TREE_CODE (arg0) != PLUS_EXPR)
>>> + arg0 = NULL_TREE;
>>> + else if (TREE_CODE (TREE_OPERAND (arg0, 0))
>>> + == INTEGER_CST
>>> + && tree_int_cst_equal (cookie_size,
>>> + TREE_OPERAND (arg0,
>>> + 0)))
>>> + {
>>> + arg0 = TREE_OPERAND (arg0, 1);
>>> + STRIP_NOPS (arg0);
>>> + }
>>> + else if (TREE_CODE (TREE_OPERAND (arg0, 1))
>>> + == INTEGER_CST
>>> + && tree_int_cst_equal (cookie_size,
>>> + TREE_OPERAND (arg0,
>>> + 1)))
>>> + {
>>> + arg0 = TREE_OPERAND (arg0, 0);
>>> + STRIP_NOPS (arg0);
>>> + }
>>> + else
>>> + arg0 = NULL_TREE;
>>> + }
>>> + if (arg0 && TREE_CODE (arg0) == MULT_EXPR)
>>> + {
>>> + tree op0 = TREE_OPERAND (arg0, 0);
>>> + tree op1 = TREE_OPERAND (arg0, 1);
>>> + var_size_adjusted = true;
>>> + if (integer_zerop (op0))
>>> + var_size
>>> + = cxx_eval_constant_expression (ctx, op1, false,
>>> + non_constant_p,
>>> + overflow_p);
>>> + else if (integer_zerop (op1))
>>> + var_size
>>> + = cxx_eval_constant_expression (ctx, op0, false,
>>> + non_constant_p,
>>> + overflow_p);
>>> + else
>>> + var_size_adjusted = false;
>>> + }
>>> + }
>>> TREE_TYPE (var)
>>> = build_new_constexpr_heap_type (elt_type, cookie_size,
>>> - var_size);
>>> + var_size, var_size_adjusted);
>>> TREE_TYPE (TREE_OPERAND (op, 0))
>>> = build_pointer_type (TREE_TYPE (var));
>>> }
>
> Jakub
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] c++, v2: Fix up constexpr evaluation of new with zero sized types [PR104568]
2022-03-15 20:19 ` Jason Merrill
@ 2022-03-16 16:55 ` Jakub Jelinek
2022-03-18 16:46 ` Jason Merrill
0 siblings, 1 reply; 6+ messages in thread
From: Jakub Jelinek @ 2022-03-16 16:55 UTC (permalink / raw)
To: Jason Merrill; +Cc: gcc-patches
On Tue, Mar 15, 2022 at 04:19:05PM -0400, Jason Merrill wrote:
> > But if you strongly prefer it that way, I can do that.
> > Note, probably not 3 new args but 4, depends on whether we could turn
> > all those cases where the tree arg0 = CALL_EXPR_ARG (oldop, 0);
> > is done but var_size_adjusted is false into assertion failures.
> > I'm worried that with the zero size of element we could end up with
> > a variable number of elements which when multiplied by 0 gives constant 0,
> > though hopefully that would be rejected earlier during constant evaluation.
>
> Or we could move all the adjustment into a separate function and only ever
> pass the number of elements to build_new_constexpr_heap_type?
So like this?
2022-03-16 Jakub Jelinek <jakub@redhat.com>
PR c++/104568
* init.cc (build_new_constexpr_heap_type): Remove FULL_SIZE
argument and its handling, instead add ITYPE2 argument. Only
support COOKIE_SIZE != NULL.
(build_new_1): If size is 0, change it to 0 * outer_nelts if
outer_nelts is non-NULL. Pass type rather than elt_type to
maybe_wrap_new_for_constexpr.
* constexpr.cc (build_new_constexpr_heap_type): New function.
(cxx_eval_constant_expression) <case CONVERT_EXPR>:
If elt_size is zero sized type, try to recover outer_nelts from
the size argument to operator new/new[] and pass that as
arg_size to build_new_constexpr_heap_type. Pass ctx,
non_constant_p and overflow_p to that call too.
* g++.dg/cpp2a/constexpr-new22.C: New test.
--- gcc/cp/constexpr.cc.jj 2022-03-16 15:25:26.294551244 +0100
+++ gcc/cp/constexpr.cc 2022-03-16 17:27:08.202184961 +0100
@@ -6422,6 +6422,84 @@ maybe_warn_about_constant_value (locatio
}
}
+/* For element type ELT_TYPE, return the appropriate type of the heap object
+ containing such element(s). COOKIE_SIZE is NULL or the size of cookie
+ in bytes. If COOKIE_SIZE is NULL, return array type
+ ELT_TYPE[FULL_SIZE / sizeof(ELT_TYPE)], otherwise return
+ struct { size_t[COOKIE_SIZE/sizeof(size_t)]; ELT_TYPE[N]; }
+ where N is is computed such that the size of the struct fits into FULL_SIZE.
+ If ARG_SIZE is non-NULL, it is the first argument to the new operator.
+ It should be passed if ELT_TYPE is zero sized type in which case FULL_SIZE
+ will be also 0 and so it is not possible to determine the actual array
+ size. CTX, NON_CONSTANT_P and OVERFLOW_P are used during constant
+ expression evaluation of subexpressions of ARG_SIZE. */
+
+tree
+build_new_constexpr_heap_type (const constexpr_ctx *ctx, tree elt_type,
+ tree cookie_size, tree full_size, tree arg_size,
+ bool *non_constant_p, bool *overflow_p)
+{
+ gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size));
+ gcc_assert (tree_fits_uhwi_p (full_size));
+ unsigned HOST_WIDE_INT csz = cookie_size ? tree_to_uhwi (cookie_size) : 0;
+ if (arg_size)
+ {
+ STRIP_NOPS (arg_size);
+ if (cookie_size)
+ {
+ if (TREE_CODE (arg_size) != PLUS_EXPR)
+ arg_size = NULL_TREE;
+ else if (TREE_CODE (TREE_OPERAND (arg_size, 0)) == INTEGER_CST
+ && tree_int_cst_equal (cookie_size,
+ TREE_OPERAND (arg_size, 0)))
+ {
+ arg_size = TREE_OPERAND (arg_size, 1);
+ STRIP_NOPS (arg_size);
+ }
+ else if (TREE_CODE (TREE_OPERAND (arg_size, 1)) == INTEGER_CST
+ && tree_int_cst_equal (cookie_size,
+ TREE_OPERAND (arg_size, 1)))
+ {
+ arg_size = TREE_OPERAND (arg_size, 0);
+ STRIP_NOPS (arg_size);
+ }
+ else
+ arg_size = NULL_TREE;
+ }
+ if (arg_size && TREE_CODE (arg_size) == MULT_EXPR)
+ {
+ tree op0 = TREE_OPERAND (arg_size, 0);
+ tree op1 = TREE_OPERAND (arg_size, 1);
+ if (integer_zerop (op0))
+ arg_size
+ = cxx_eval_constant_expression (ctx, op1, false, non_constant_p,
+ overflow_p);
+ else if (integer_zerop (op1))
+ arg_size
+ = cxx_eval_constant_expression (ctx, op0, false, non_constant_p,
+ overflow_p);
+ else
+ arg_size = NULL_TREE;
+ }
+ else
+ arg_size = NULL_TREE;
+ }
+
+ unsigned HOST_WIDE_INT fsz = tree_to_uhwi (arg_size ? arg_size : full_size);
+ unsigned HOST_WIDE_INT esz = int_size_in_bytes (elt_type);
+ if (!arg_size)
+ {
+ gcc_assert (fsz >= csz);
+ fsz -= csz;
+ if (esz)
+ fsz /= esz;
+ }
+ tree itype2 = build_index_type (size_int (fsz - 1));
+ if (!cookie_size)
+ return build_cplus_array_type (elt_type, itype2);
+ return build_new_constexpr_heap_type (elt_type, cookie_size, itype2);
+}
+
/* Attempt to reduce the expression T to a constant value.
On failure, issue diagnostic and return error_mark_node. */
/* FIXME unify with c_fully_fold */
@@ -7253,6 +7331,7 @@ cxx_eval_constant_expression (const cons
tree var_size = TYPE_SIZE_UNIT (TREE_TYPE (var));
tree elt_type = TREE_TYPE (type);
tree cookie_size = NULL_TREE;
+ tree arg_size = NULL_TREE;
if (TREE_CODE (elt_type) == RECORD_TYPE
&& TYPE_NAME (elt_type) == heap_identifier)
{
@@ -7264,9 +7343,21 @@ cxx_eval_constant_expression (const cons
DECL_NAME (var)
= (DECL_NAME (var) == heap_uninit_identifier
? heap_identifier : heap_vec_identifier);
+ /* For zero sized elt_type, try to recover how many outer_nelts
+ it should have. */
+ if ((cookie_size ? tree_int_cst_equal (var_size, cookie_size)
+ : integer_zerop (var_size))
+ && !int_size_in_bytes (elt_type)
+ && TREE_CODE (oldop) == CALL_EXPR
+ && call_expr_nargs (oldop) >= 1)
+ if (tree fun = get_function_named_in_call (oldop))
+ if (cxx_replaceable_global_alloc_fn (fun)
+ && IDENTIFIER_NEW_OP_P (DECL_NAME (fun)))
+ arg_size = CALL_EXPR_ARG (oldop, 0);
TREE_TYPE (var)
- = build_new_constexpr_heap_type (elt_type, cookie_size,
- var_size);
+ = build_new_constexpr_heap_type (ctx, elt_type, cookie_size,
+ var_size, arg_size,
+ non_constant_p, overflow_p);
TREE_TYPE (TREE_OPERAND (op, 0))
= build_pointer_type (TREE_TYPE (var));
}
--- gcc/cp/init.cc.jj 2022-03-16 15:25:26.431549398 +0100
+++ gcc/cp/init.cc 2022-03-16 17:23:03.922500101 +0100
@@ -2931,33 +2931,17 @@ std_placement_new_fn_p (tree alloc_fn)
}
/* For element type ELT_TYPE, return the appropriate type of the heap object
- containing such element(s). COOKIE_SIZE is NULL or the size of cookie
- in bytes. FULL_SIZE is NULL if it is unknown how big the heap allocation
- will be, otherwise size of the heap object. If COOKIE_SIZE is NULL,
- return array type ELT_TYPE[FULL_SIZE / sizeof(ELT_TYPE)], otherwise return
+ containing such element(s). COOKIE_SIZE is the size of cookie in bytes.
+ Return
struct { size_t[COOKIE_SIZE/sizeof(size_t)]; ELT_TYPE[N]; }
- where N is nothing (flexible array member) if FULL_SIZE is NULL, otherwise
- it is computed such that the size of the struct fits into FULL_SIZE. */
+ where N is nothing (flexible array member) if ITYPE2 is NULL, otherwise
+ the array has ITYPE2 as its TYPE_DOMAIN. */
tree
-build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree full_size)
+build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree itype2)
{
- gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size));
- gcc_assert (full_size == NULL_TREE || tree_fits_uhwi_p (full_size));
- unsigned HOST_WIDE_INT csz = cookie_size ? tree_to_uhwi (cookie_size) : 0;
- tree itype2 = NULL_TREE;
- if (full_size)
- {
- unsigned HOST_WIDE_INT fsz = tree_to_uhwi (full_size);
- gcc_assert (fsz >= csz);
- fsz -= csz;
- fsz /= int_size_in_bytes (elt_type);
- itype2 = build_index_type (size_int (fsz - 1));
- if (!cookie_size)
- return build_cplus_array_type (elt_type, itype2);
- }
- else
- gcc_assert (cookie_size);
+ gcc_assert (tree_fits_uhwi_p (cookie_size));
+ unsigned HOST_WIDE_INT csz = tree_to_uhwi (cookie_size);
csz /= int_size_in_bytes (sizetype);
tree itype1 = build_index_type (size_int (csz - 1));
tree atype1 = build_cplus_array_type (sizetype, itype1);
@@ -3408,6 +3392,12 @@ build_new_1 (vec<tree, va_gc> **placemen
outer_nelts_check = NULL_TREE;
}
+ /* If size is zero e.g. due to type having zero size, try to
+ preserve outer_nelts for constant expression evaluation
+ purposes. */
+ if (integer_zerop (size) && outer_nelts)
+ size = build2 (MULT_EXPR, TREE_TYPE (size), size, outer_nelts);
+
alloc_call = build_operator_new_call (fnname, placement,
&size, &cookie_size,
align_arg, outer_nelts_check,
@@ -3484,7 +3474,7 @@ build_new_1 (vec<tree, va_gc> **placemen
}
if (cookie_size)
- alloc_call = maybe_wrap_new_for_constexpr (alloc_call, elt_type,
+ alloc_call = maybe_wrap_new_for_constexpr (alloc_call, type,
cookie_size);
/* In the simple case, we can stop now. */
--- gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C.jj 2022-03-16 16:45:04.011372629 +0100
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C 2022-03-16 16:45:04.011372629 +0100
@@ -0,0 +1,42 @@
+// PR c++/104568
+// { dg-do compile { target c++20 } }
+// { dg-options "" }
+
+struct S { int s; constexpr S () : s (0) {} constexpr ~S () {} };
+typedef int T[0];
+typedef int U[0];
+
+constexpr bool
+foo ()
+{
+ auto p = new T[2];
+ auto q1 = &p[0];
+ auto q2 = &p[1];
+ auto q3 = &p[2];
+ delete[] p;
+ return true;
+}
+
+constexpr bool
+bar ()
+{
+ auto p = new U[2];
+ auto q1 = &p[0];
+ auto q2 = &p[1];
+ auto q3 = &p[2];
+ delete[] p;
+ return true;
+}
+
+constexpr bool
+baz ()
+{
+ auto p = new T[0];
+ auto q1 = &p[0];
+ delete[] p;
+ return true;
+}
+
+constexpr bool a = foo ();
+constexpr bool b = bar ();
+constexpr bool c = baz ();
Jakub
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] c++, v2: Fix up constexpr evaluation of new with zero sized types [PR104568]
2022-03-16 16:55 ` [PATCH] c++, v2: " Jakub Jelinek
@ 2022-03-18 16:46 ` Jason Merrill
0 siblings, 0 replies; 6+ messages in thread
From: Jason Merrill @ 2022-03-18 16:46 UTC (permalink / raw)
To: Jakub Jelinek; +Cc: gcc-patches
On 3/16/22 12:55, Jakub Jelinek wrote:
> On Tue, Mar 15, 2022 at 04:19:05PM -0400, Jason Merrill wrote:
>>> But if you strongly prefer it that way, I can do that.
>>> Note, probably not 3 new args but 4, depends on whether we could turn
>>> all those cases where the tree arg0 = CALL_EXPR_ARG (oldop, 0);
>>> is done but var_size_adjusted is false into assertion failures.
>>> I'm worried that with the zero size of element we could end up with
>>> a variable number of elements which when multiplied by 0 gives constant 0,
>>> though hopefully that would be rejected earlier during constant evaluation.
>>
>> Or we could move all the adjustment into a separate function and only ever
>> pass the number of elements to build_new_constexpr_heap_type?
>
> So like this?
>
> 2022-03-16 Jakub Jelinek <jakub@redhat.com>
>
> PR c++/104568
> * init.cc (build_new_constexpr_heap_type): Remove FULL_SIZE
> argument and its handling, instead add ITYPE2 argument. Only
> support COOKIE_SIZE != NULL.
> (build_new_1): If size is 0, change it to 0 * outer_nelts if
> outer_nelts is non-NULL. Pass type rather than elt_type to
> maybe_wrap_new_for_constexpr.
> * constexpr.cc (build_new_constexpr_heap_type): New function.
> (cxx_eval_constant_expression) <case CONVERT_EXPR>:
> If elt_size is zero sized type, try to recover outer_nelts from
> the size argument to operator new/new[] and pass that as
> arg_size to build_new_constexpr_heap_type. Pass ctx,
> non_constant_p and overflow_p to that call too.
>
> * g++.dg/cpp2a/constexpr-new22.C: New test.
>
> --- gcc/cp/constexpr.cc.jj 2022-03-16 15:25:26.294551244 +0100
> +++ gcc/cp/constexpr.cc 2022-03-16 17:27:08.202184961 +0100
> @@ -6422,6 +6422,84 @@ maybe_warn_about_constant_value (locatio
> }
> }
>
> +/* For element type ELT_TYPE, return the appropriate type of the heap object
> + containing such element(s). COOKIE_SIZE is NULL or the size of cookie
> + in bytes. If COOKIE_SIZE is NULL, return array type
> + ELT_TYPE[FULL_SIZE / sizeof(ELT_TYPE)], otherwise return
> + struct { size_t[COOKIE_SIZE/sizeof(size_t)]; ELT_TYPE[N]; }
> + where N is is computed such that the size of the struct fits into FULL_SIZE.
> + If ARG_SIZE is non-NULL, it is the first argument to the new operator.
> + It should be passed if ELT_TYPE is zero sized type in which case FULL_SIZE
> + will be also 0 and so it is not possible to determine the actual array
> + size. CTX, NON_CONSTANT_P and OVERFLOW_P are used during constant
> + expression evaluation of subexpressions of ARG_SIZE. */
> +
> +tree
Let's make this static.
> +build_new_constexpr_heap_type (const constexpr_ctx *ctx, tree elt_type,
> + tree cookie_size, tree full_size, tree arg_size,
> + bool *non_constant_p, bool *overflow_p)
> +{
> + gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size));
> + gcc_assert (tree_fits_uhwi_p (full_size));
> + unsigned HOST_WIDE_INT csz = cookie_size ? tree_to_uhwi (cookie_size) : 0;
> + if (arg_size)
> + {
> + STRIP_NOPS (arg_size);
> + if (cookie_size)
> + {
> + if (TREE_CODE (arg_size) != PLUS_EXPR)
> + arg_size = NULL_TREE;
> + else if (TREE_CODE (TREE_OPERAND (arg_size, 0)) == INTEGER_CST
> + && tree_int_cst_equal (cookie_size,
> + TREE_OPERAND (arg_size, 0)))
> + {
> + arg_size = TREE_OPERAND (arg_size, 1);
> + STRIP_NOPS (arg_size);
> + }
> + else if (TREE_CODE (TREE_OPERAND (arg_size, 1)) == INTEGER_CST
> + && tree_int_cst_equal (cookie_size,
> + TREE_OPERAND (arg_size, 1)))
> + {
> + arg_size = TREE_OPERAND (arg_size, 0);
> + STRIP_NOPS (arg_size);
> + }
> + else
> + arg_size = NULL_TREE;
> + }
> + if (arg_size && TREE_CODE (arg_size) == MULT_EXPR)
> + {
> + tree op0 = TREE_OPERAND (arg_size, 0);
> + tree op1 = TREE_OPERAND (arg_size, 1);
> + if (integer_zerop (op0))
> + arg_size
> + = cxx_eval_constant_expression (ctx, op1, false, non_constant_p,
> + overflow_p);
> + else if (integer_zerop (op1))
> + arg_size
> + = cxx_eval_constant_expression (ctx, op0, false, non_constant_p,
> + overflow_p);
> + else
> + arg_size = NULL_TREE;
> + }
> + else
> + arg_size = NULL_TREE;
> + }
> +
> + unsigned HOST_WIDE_INT fsz = tree_to_uhwi (arg_size ? arg_size : full_size);
> + unsigned HOST_WIDE_INT esz = int_size_in_bytes (elt_type);
esz could move inside the if.
OK with those changes, thanks.
> + if (!arg_size)
> + {
> + gcc_assert (fsz >= csz);
> + fsz -= csz;
> + if (esz)
> + fsz /= esz;
> + }
> + tree itype2 = build_index_type (size_int (fsz - 1));
> + if (!cookie_size)
> + return build_cplus_array_type (elt_type, itype2);
> + return build_new_constexpr_heap_type (elt_type, cookie_size, itype2);
> +}
> +
> /* Attempt to reduce the expression T to a constant value.
> On failure, issue diagnostic and return error_mark_node. */
> /* FIXME unify with c_fully_fold */
> @@ -7253,6 +7331,7 @@ cxx_eval_constant_expression (const cons
> tree var_size = TYPE_SIZE_UNIT (TREE_TYPE (var));
> tree elt_type = TREE_TYPE (type);
> tree cookie_size = NULL_TREE;
> + tree arg_size = NULL_TREE;
> if (TREE_CODE (elt_type) == RECORD_TYPE
> && TYPE_NAME (elt_type) == heap_identifier)
> {
> @@ -7264,9 +7343,21 @@ cxx_eval_constant_expression (const cons
> DECL_NAME (var)
> = (DECL_NAME (var) == heap_uninit_identifier
> ? heap_identifier : heap_vec_identifier);
> + /* For zero sized elt_type, try to recover how many outer_nelts
> + it should have. */
> + if ((cookie_size ? tree_int_cst_equal (var_size, cookie_size)
> + : integer_zerop (var_size))
> + && !int_size_in_bytes (elt_type)
> + && TREE_CODE (oldop) == CALL_EXPR
> + && call_expr_nargs (oldop) >= 1)
> + if (tree fun = get_function_named_in_call (oldop))
> + if (cxx_replaceable_global_alloc_fn (fun)
> + && IDENTIFIER_NEW_OP_P (DECL_NAME (fun)))
> + arg_size = CALL_EXPR_ARG (oldop, 0);
> TREE_TYPE (var)
> - = build_new_constexpr_heap_type (elt_type, cookie_size,
> - var_size);
> + = build_new_constexpr_heap_type (ctx, elt_type, cookie_size,
> + var_size, arg_size,
> + non_constant_p, overflow_p);
> TREE_TYPE (TREE_OPERAND (op, 0))
> = build_pointer_type (TREE_TYPE (var));
> }
> --- gcc/cp/init.cc.jj 2022-03-16 15:25:26.431549398 +0100
> +++ gcc/cp/init.cc 2022-03-16 17:23:03.922500101 +0100
> @@ -2931,33 +2931,17 @@ std_placement_new_fn_p (tree alloc_fn)
> }
>
> /* For element type ELT_TYPE, return the appropriate type of the heap object
> - containing such element(s). COOKIE_SIZE is NULL or the size of cookie
> - in bytes. FULL_SIZE is NULL if it is unknown how big the heap allocation
> - will be, otherwise size of the heap object. If COOKIE_SIZE is NULL,
> - return array type ELT_TYPE[FULL_SIZE / sizeof(ELT_TYPE)], otherwise return
> + containing such element(s). COOKIE_SIZE is the size of cookie in bytes.
> + Return
> struct { size_t[COOKIE_SIZE/sizeof(size_t)]; ELT_TYPE[N]; }
> - where N is nothing (flexible array member) if FULL_SIZE is NULL, otherwise
> - it is computed such that the size of the struct fits into FULL_SIZE. */
> + where N is nothing (flexible array member) if ITYPE2 is NULL, otherwise
> + the array has ITYPE2 as its TYPE_DOMAIN. */
>
> tree
> -build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree full_size)
> +build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree itype2)
> {
> - gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size));
> - gcc_assert (full_size == NULL_TREE || tree_fits_uhwi_p (full_size));
> - unsigned HOST_WIDE_INT csz = cookie_size ? tree_to_uhwi (cookie_size) : 0;
> - tree itype2 = NULL_TREE;
> - if (full_size)
> - {
> - unsigned HOST_WIDE_INT fsz = tree_to_uhwi (full_size);
> - gcc_assert (fsz >= csz);
> - fsz -= csz;
> - fsz /= int_size_in_bytes (elt_type);
> - itype2 = build_index_type (size_int (fsz - 1));
> - if (!cookie_size)
> - return build_cplus_array_type (elt_type, itype2);
> - }
> - else
> - gcc_assert (cookie_size);
> + gcc_assert (tree_fits_uhwi_p (cookie_size));
> + unsigned HOST_WIDE_INT csz = tree_to_uhwi (cookie_size);
> csz /= int_size_in_bytes (sizetype);
> tree itype1 = build_index_type (size_int (csz - 1));
> tree atype1 = build_cplus_array_type (sizetype, itype1);
> @@ -3408,6 +3392,12 @@ build_new_1 (vec<tree, va_gc> **placemen
> outer_nelts_check = NULL_TREE;
> }
>
> + /* If size is zero e.g. due to type having zero size, try to
> + preserve outer_nelts for constant expression evaluation
> + purposes. */
> + if (integer_zerop (size) && outer_nelts)
> + size = build2 (MULT_EXPR, TREE_TYPE (size), size, outer_nelts);
> +
> alloc_call = build_operator_new_call (fnname, placement,
> &size, &cookie_size,
> align_arg, outer_nelts_check,
> @@ -3484,7 +3474,7 @@ build_new_1 (vec<tree, va_gc> **placemen
> }
>
> if (cookie_size)
> - alloc_call = maybe_wrap_new_for_constexpr (alloc_call, elt_type,
> + alloc_call = maybe_wrap_new_for_constexpr (alloc_call, type,
> cookie_size);
>
> /* In the simple case, we can stop now. */
> --- gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C.jj 2022-03-16 16:45:04.011372629 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C 2022-03-16 16:45:04.011372629 +0100
> @@ -0,0 +1,42 @@
> +// PR c++/104568
> +// { dg-do compile { target c++20 } }
> +// { dg-options "" }
> +
> +struct S { int s; constexpr S () : s (0) {} constexpr ~S () {} };
> +typedef int T[0];
> +typedef int U[0];
> +
> +constexpr bool
> +foo ()
> +{
> + auto p = new T[2];
> + auto q1 = &p[0];
> + auto q2 = &p[1];
> + auto q3 = &p[2];
> + delete[] p;
> + return true;
> +}
> +
> +constexpr bool
> +bar ()
> +{
> + auto p = new U[2];
> + auto q1 = &p[0];
> + auto q2 = &p[1];
> + auto q3 = &p[2];
> + delete[] p;
> + return true;
> +}
> +
> +constexpr bool
> +baz ()
> +{
> + auto p = new T[0];
> + auto q1 = &p[0];
> + delete[] p;
> + return true;
> +}
> +
> +constexpr bool a = foo ();
> +constexpr bool b = bar ();
> +constexpr bool c = baz ();
>
>
> Jakub
>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-03-18 16:46 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-02-21 8:25 [PATCH] c++: Fix up constexpr evaluation of new with zero sized types [PR104568] Jakub Jelinek
2022-03-12 4:28 ` Jason Merrill
2022-03-15 11:44 ` Jakub Jelinek
2022-03-15 20:19 ` Jason Merrill
2022-03-16 16:55 ` [PATCH] c++, v2: " Jakub Jelinek
2022-03-18 16:46 ` Jason Merrill
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