On 5/7/20 10:55 AM, Marek Polacek wrote:
On Wed, May 06, 2020 at 05:26:32PM -0400, Jason Merrill wrote:
On 5/5/20 6:17 PM, Marek Polacek wrote:
An ICE arises here because we call cp_get_callee_fndecl_nofold in a
template, and we've got a CALL_EXPR whose CALL_EXPR_FN is a BASELINK.
This tickles the INDIRECT_TYPE_P assert in cp_get_fndecl_from_callee.
Jakub said in the PR that he'd hit a similar problem too and dealt
with it in omp_declare_variant_finalize_one. I considered tweaking
is_std_constant_evaluated_p to return false for a BASELINK, since the
std::is_constant_evaluated call we're looking for can't be a member
function, but perhaps we could get another unexpected CALL_EXPR and
crash the same. In which case it might be better to make out the
omp_* code into a new routine and use that, as below.
Why not adjust cp_get_fndecl_from_callee to, say, return null instead of
aborting when !INDIRECT_TYPE_P?
It's often hard (for me, anyway) to decide if an assert should stay or can
be turned into a condition. In this case we could argue that initially
cp_get_fndecl_from_callee wasn't meant to be called in a template, but now
we have reasonable use cases where it actually is called in a template, so
should cope instead of crashing. Is that a fair assesment?
Yes, when we hit an assert we always have to decide whether the assert
is catching a problem elsewhere or being too strict. I think the
unsuitability to template trees was accidental rather than deliberate.
I suspect one could argue that if we see a BASELINK, we might want to use
BASELINK_FUNCTIONS to get the FUNCTION_DECL, but I don't have a test where
that would make a difference.
In a template we end up with CALL_EXPR_FN that refers to the overload
set; even if we were able to do overload resolution and chose a function
to call, we've discarded that information.
We could restrict the added null return to
processing_template_decl && is_overloaded_fn (fn)
but I'm not sure that retaining that much of the assert is actually
valuable.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/10.2?
OK.
-- >8 --
An ICE arises here because we call cp_get_callee_fndecl_nofold in a
template, and we've got a CALL_EXPR whose CALL_EXPR_FN is a BASELINK.
This tickles the INDIRECT_TYPE_P assert in cp_get_fndecl_from_callee.
Fixed by turning the assert into a condition and returning NULL_TREE
in that case.
PR c++/94937
* cvt.c (cp_get_fndecl_from_callee): Return NULL_TREE if the function
type is not INDIRECT_TYPE_P.
* decl.c (omp_declare_variant_finalize_one): Call
cp_get_callee_fndecl_nofold instead of looking for the function decl
manually.
* g++.dg/cpp1z/constexpr-if34.C: New test.
* g++.dg/cpp2a/is-constant-evaluated10.C: New test.
---
gcc/cp/cvt.c | 3 +-
gcc/cp/decl.c | 12 +-------
gcc/testsuite/g++.dg/cpp1z/constexpr-if34.C | 15 ++++++++++
.../g++.dg/cpp2a/is-constant-evaluated10.C | 30 +++++++++++++++++++
4 files changed, 47 insertions(+), 13 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if34.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated10.C
diff --git a/gcc/cp/cvt.c b/gcc/cp/cvt.c
index 656e7fd3ec0..371002833d0 100644
--- a/gcc/cp/cvt.c
+++ b/gcc/cp/cvt.c
@@ -995,9 +995,8 @@ cp_get_fndecl_from_callee (tree fn, bool fold /* = true */)
if (TREE_CODE (fn) == FUNCTION_DECL)
return fn;
tree type = TREE_TYPE (fn);
- if (type == unknown_type_node)
+ if (type == NULL_TREE || !INDIRECT_TYPE_P (type))
return NULL_TREE;
- gcc_assert (INDIRECT_TYPE_P (type));
if (fold)
fn = maybe_constant_init (fn);
STRIP_NOPS (fn);
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 232d7ed4a14..cbdef3e3365 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -7297,17 +7297,7 @@ omp_declare_variant_finalize_one (tree decl, tree attr)
if (variant == error_mark_node && !processing_template_decl)
return true;
- variant = cp_get_callee (variant);
- if (variant)
- {
- if (TREE_CODE (variant) == FUNCTION_DECL)
- ;
- else if (TREE_TYPE (variant) && INDIRECT_TYPE_P (TREE_TYPE (variant)))
- variant = cp_get_fndecl_from_callee (variant, false);
- else
- variant = NULL_TREE;
- }
-
+ variant = cp_get_callee_fndecl_nofold (variant);
input_location = save_loc;
if (variant)
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if34.C
b/gcc/testsuite/g++.dg/cpp1z/constexpr-if34.C
new file mode 100644
index 00000000000..6e0b2597a53
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if34.C
@@ -0,0 +1,15 @@
+// PR c++/94937 - ICE with -Wall and constexpr if.
+// { dg-do compile { target c++17 } }
+// { dg-options "-Wall" }
+
+struct B {
+ static constexpr bool foo() { return false; }
+};
+
+template<typename T>
+struct C {
+ static void bar ()
+ {
+ if constexpr (B::foo()) ;
+ }
+};
diff --git a/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated10.C
b/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated10.C
new file mode 100644
index 00000000000..7b2e345f448
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated10.C
@@ -0,0 +1,30 @@
+// { dg-do compile { target c++2a } }
+// { dg-options "-Wtautological-compare" }
+
+namespace std {
+ constexpr inline bool
+ is_constant_evaluated () noexcept
+ {
+ return __builtin_is_constant_evaluated ();
+ }
+}
+
+template<typename>
+constexpr int
+foo(int i)
+{
+ if constexpr (std::is_constant_evaluated ()) // { dg-warning
".std::is_constant_evaluated. always evaluates to true in .if constexpr." }
+ return 42;
+ else
+ return i;
+}
+
+template<typename>
+constexpr int
+foo2(int i)
+{
+ if constexpr (__builtin_is_constant_evaluated ()) // { dg-warning
".std::is_constant_evaluated. always evaluates to true in .if constexpr." }
+ return 42;
+ else
+ return i;
+}
base-commit: 9cd70f3f0fa45cbe899da5ecd0b0c6da0657fd62
