On Tue, Mar 04, 2025 at 05:34:10PM -0500, Jason Merrill wrote:
> On 2/11/25 6:24 PM, Marek Polacek wrote:
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> >
> > -- >8 --
> > Here we ICE since r11-7740 because we no longer say that (long)&a
> > (where a is a global var) is non_constant_p. So VERIFY_CONSTANT
> > does not return and we crash on tree_to_uhwi. We should check
> > tree_fits_uhwi_p before calling tree_to_uhwi.
> >
> > PR c++/118775
> >
> > gcc/cp/ChangeLog:
> >
> > * constexpr.cc (cxx_eval_call_expression): Check tree_fits_uhwi_p.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/cpp2a/constexpr-new24.C: New test.
> > * g++.dg/cpp2a/constexpr-new25.C: New test.
> > ---
> > gcc/cp/constexpr.cc | 7 +++++
> > gcc/testsuite/g++.dg/cpp2a/constexpr-new24.C | 25 ++++++++++++++++++
> > gcc/testsuite/g++.dg/cpp2a/constexpr-new25.C | 27 ++++++++++++++++++++
> > 3 files changed, 59 insertions(+)
> > create mode 100644 gcc/testsuite/g++.dg/cpp2a/constexpr-new24.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp2a/constexpr-new25.C
> >
> > diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> > index f142dd32bc8..f8f9a9df1a2 100644
> > --- a/gcc/cp/constexpr.cc
> > +++ b/gcc/cp/constexpr.cc
> > @@ -2909,6 +2909,13 @@ cxx_eval_call_expression (const constexpr_ctx *ctx,
> > tree t,
> > gcc_assert (arg0);
> > if (new_op_p)
> > {
> > + if (!tree_fits_uhwi_p (arg0))
> > + {
> > + if (!ctx->quiet)
> > + error_at (loc, "cannot allocate array: size too large");
>
> "too large" seems misleading in this case, where it just isn't a
> compile-time constant.
Fair, how about "size not constant"?
> Why didn't the VERIFY_CONSTANT just above already reject this?
This is about *non_constant_p. Since r11-7740 cxx_eval_constant_expression
returns early less often:
@@ -6656,7 +6656,8 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx,
tree t,
if (TREE_CODE (t) == CONVERT_EXPR
&& ARITHMETIC_TYPE_P (type)
- && INDIRECT_TYPE_P (TREE_TYPE (op)))
+ && INDIRECT_TYPE_P (TREE_TYPE (op))
+ && ctx->manifestly_const_eval)
{
if (!ctx->quiet)
error_at (loc,
and in constexpr-new25.C it doesn't signal that the expression is non-constant.
Before r11-7740 we wouldn't get past the VERIFY_CONSTANT here:
tree arg = CALL_EXPR_ARG (t, i);
arg = cxx_eval_constant_expression (ctx, arg, vc_prvalue,
non_constant_p, overflow_p);
/* Deleting a non-constant pointer has a better error message
below. */
if (new_op_p || i != 0)
VERIFY_CONSTANT (arg);
but now we do since *non_constant_p is false and reduced_constant_expression_p
is fine with (long unsigned int) &a.
-- >8 --
Here we ICE since r11-7740 because we no longer say that (long)&a
(where a is a global var) is non_constant_p. So VERIFY_CONSTANT
does not return and we crash on tree_to_uhwi. We should check
tree_fits_uhwi_p before calling tree_to_uhwi.
PR c++/118775
gcc/cp/ChangeLog:
* constexpr.cc (cxx_eval_call_expression): Check tree_fits_uhwi_p.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/constexpr-new24.C: New test.
* g++.dg/cpp2a/constexpr-new25.C: New test.
---
gcc/cp/constexpr.cc | 7 +++++
gcc/testsuite/g++.dg/cpp2a/constexpr-new24.C | 25 ++++++++++++++++++
gcc/testsuite/g++.dg/cpp2a/constexpr-new25.C | 27 ++++++++++++++++++++
3 files changed, 59 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/constexpr-new24.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/constexpr-new25.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index aa2fa44613a..728cf3b249c 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -2928,6 +2928,13 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree
t,
gcc_assert (arg0);
if (new_op_p)
{
+ if (!tree_fits_uhwi_p (arg0))
+ {
+ if (!ctx->quiet)
+ error_at (loc, "cannot allocate array: size not constant");
+ *non_constant_p = true;
+ return t;
+ }
tree type = build_array_type_nelts (char_type_node,
tree_to_uhwi (arg0));
tree var = build_decl (loc, VAR_DECL,
diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-new24.C
b/gcc/testsuite/g++.dg/cpp2a/constexpr-new24.C
new file mode 100644
index 00000000000..ee62f18922c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-new24.C
@@ -0,0 +1,25 @@
+// PR c++/118775
+// { dg-do compile { target c++20 } }
+
+int a;
+
+constexpr char *
+f1 ()
+{
+ constexpr auto p = new char[(long int) &a]; // { dg-error "size not
constant" }
+ return p;
+}
+
+constexpr char *
+f2 ()
+{
+ auto p = new char[(long int) &a]; // { dg-error "size not constant" }
+ return p;
+}
+
+void
+g ()
+{
+ auto r1 = f2 ();
+ constexpr auto r2 = f2 (); // { dg-message "in .constexpr. expansion" }
+}
diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-new25.C
b/gcc/testsuite/g++.dg/cpp2a/constexpr-new25.C
new file mode 100644
index 00000000000..91c0318abd8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-new25.C
@@ -0,0 +1,27 @@
+// PR c++/118775
+// { dg-do compile { target c++20 } }
+
+namespace std {
+struct __uniq_ptr_impl {
+ constexpr __uniq_ptr_impl(char *) {}
+};
+template <typename> struct unique_ptr {
+ __uniq_ptr_impl _M_t;
+ constexpr ~unique_ptr() {}
+};
+template <typename> struct _MakeUniq;
+template <typename _Tp> struct _MakeUniq<_Tp[]> {
+ typedef unique_ptr<_Tp[]> __array;
+};
+template <typename _Tp> using __unique_ptr_array_t = _MakeUniq<_Tp>::__array;
+constexpr __unique_ptr_array_t<char[]> make_unique(long __num) {
+ return unique_ptr<char[]>(new char[__num]);
+}
+} // namespace std
+int a;
+int
+main ()
+{
+ std::unique_ptr p = std::make_unique((long)&a);
+ constexpr std::unique_ptr p2 = std::make_unique((long)&a); // { dg-error
"conversion" }
+}
base-commit: 4d0a333ef13e2da140cd44c4941b20f48a80dc0f
--
2.48.1
