On Thu, 7 Jan 2021, Jason Merrill wrote:
> On 1/7/21 10:10 AM, Patrick Palka wrote:
> > We shouldn't do replace_result_decl after evaluating a call that returns
> > a PMF because PMF temporaries aren't wrapped in a TARGET_EXPR (and so we
> > can't trust ctx->object), and PMF initializers can't be self-referential
> > anyway, so replace_result_decl would always be a no-op. This fixes an
> > ICE from the sanity check in replace_result_decl in the below testcase
> > during cxx_eval_call_expression of the call f() in the initializer g(f()).
> >
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > trunk?
> >
> > gcc/cp/ChangeLog:
> >
> > PR c++/98551
> > * constexpr.c (cxx_eval_call_expression): Don't call
> > replace_result_decl when the result is a PMF.
> >
> > gcc/testsuite/ChangeLog:
> >
> > PR c++/98551
> > * g++.dg/cpp0x/constexpr-pmf2.C: New test.
> > ---
> > gcc/cp/constexpr.c | 1 +
> > gcc/testsuite/g++.dg/cpp0x/constexpr-pmf2.C | 9 +++++++++
> > 2 files changed, 10 insertions(+)
> > create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-pmf2.C
> >
> > diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
> > index 0c12f608d36..a7272d49d0d 100644
> > --- a/gcc/cp/constexpr.c
> > +++ b/gcc/cp/constexpr.c
> > @@ -2788,6 +2788,7 @@ cxx_eval_call_expression (const constexpr_ctx *ctx,
> > tree t,
> > current object under construction. */
> > if (!*non_constant_p && ctx->object
> > && AGGREGATE_TYPE_P (TREE_TYPE (res))
> > + && !TYPE_PTRMEMFUNC_P (TREE_TYPE (res))
>
> It ought to work to change AGGREGATE_TYPE_P to CLASS_TYPE_P; we can't return
> an array, and a vector can't contain a pointer to itself.
>
> Alternately, we could change the same-type assert in replace_result_decl to a
> test and return false if different.
>
> OK with either change.
Sounds good. I went with changing AGGREGATE_TYPE_P to CLASS_TYPE_P and
leaving alone the assert in replace_result_decl for now:
-- >8 --
Subject: [PATCH] c++: ICE with constexpr call that returns a PMF [PR98551]
We shouldn't do replace_result_decl after evaluating a call that returns
a PMF because PMF temporaries aren't wrapped in a TARGET_EXPR (and so we
can't trust ctx->object), and PMF initializers can't be self-referential
anyway, so replace_result_decl would always be a no-op.
To that end, this patch changes the relevant AGGREGATE_TYPE_P test to
CLASS_TYPE_P, which should rule out PMFs (as well as arrays, which we
can't return and therefore won't see here). This fixes an ICE from the
sanity check in replace_result_decl in the below testcase during
constexpr evaluation of the call f() in the initializer g(f()).
gcc/cp/ChangeLog:
PR c++/98551
* constexpr.c (cxx_eval_call_expression): Check CLASS_TYPE_P
instead of AGGREGATE_TYPE_P before calling replace_result_decl.
gcc/testsuite/ChangeLog:
PR c++/98551
* g++.dg/cpp0x/constexpr-pmf2.C: New test.
---
gcc/cp/constexpr.c | 2 +-
gcc/testsuite/g++.dg/cpp0x/constexpr-pmf2.C | 9 +++++++++
2 files changed, 10 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-pmf2.C
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 4a5e6384da6..9dddc53ca52 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -2790,7 +2790,7 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree
t,
/* Rewrite all occurrences of the function's RESULT_DECL with the
current object under construction. */
if (!*non_constant_p && ctx->object
- && AGGREGATE_TYPE_P (TREE_TYPE (res))
+ && CLASS_TYPE_P (TREE_TYPE (res))
&& !is_empty_class (TREE_TYPE (res)))
if (replace_result_decl (&result, res, ctx->object))
cacheable = false;
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-pmf2.C
b/gcc/testsuite/g++.dg/cpp0x/constexpr-pmf2.C
new file mode 100644
index 00000000000..a76e712afe1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-pmf2.C
@@ -0,0 +1,9 @@
+// PR c++/98551
+// { dg-do compile { target c++11 } }
+
+struct A {};
+struct B { int t(); };
+using pmf = decltype(&B::t);
+constexpr pmf f() { return &B::t; }
+constexpr A g(pmf) { return {}; };
+constexpr A x = g(f());
--
2.30.0
