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?
As a drive-by, I'm adding a test that tests the "is_constant_evaluated
in constexpr if" warning in a template too.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/10.2?
PR c++/94937
* cp-tree.h (cp_get_callee_fndecl_template): Declare.
* cvt.c (cp_get_callee_fndecl_template): New.
* decl.c (omp_declare_variant_finalize_one): Use
cp_get_callee_fndecl_template.
* semantics.c (is_std_constant_evaluated_p): Call
cp_get_callee_fndecl_template instead of cp_get_callee_fndecl_nofold.
* g++.dg/cpp1z/constexpr-if34.C: New test.
* g++.dg/cpp2a/is-constant-evaluated10.C: New test.
---
gcc/cp/cp-tree.h | 1 +
gcc/cp/cvt.c | 17 +++++++++++
gcc/cp/decl.c | 12 +-------
gcc/cp/semantics.c | 2 +-
gcc/testsuite/g++.dg/cpp1z/constexpr-if34.C | 15 ++++++++++
.../g++.dg/cpp2a/is-constant-evaluated10.C | 30 +++++++++++++++++++
6 files changed, 65 insertions(+), 12 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/cp-tree.h b/gcc/cp/cp-tree.h
index c4b81428e14..ecee0f479b0 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6477,6 +6477,7 @@ extern tree cp_fold_convert (tree,
tree);
extern tree cp_get_callee (tree);
extern tree cp_get_callee_fndecl (tree);
extern tree cp_get_callee_fndecl_nofold (tree);
+extern tree cp_get_callee_fndecl_template (tree);
extern tree cp_get_fndecl_from_callee (tree, bool fold = true);
extern tree convert_to_void (tree, impl_conv_void,
tsubst_flags_t);
diff --git a/gcc/cp/cvt.c b/gcc/cp/cvt.c
index 656e7fd3ec0..5d3fba76bb9 100644
--- a/gcc/cp/cvt.c
+++ b/gcc/cp/cvt.c
@@ -1027,6 +1027,23 @@ cp_get_callee_fndecl_nofold (tree call)
return cp_get_fndecl_from_callee (cp_get_callee (call), false);
}
+/* As above, but is safe to call in a template too where we might get
+ unexpected trees. Returns the FUNCTION_DECL or NULL_TREE. */
+
+tree
+cp_get_callee_fndecl_template (tree call)
+{
+ call = cp_get_callee (call);
+ if (call == NULL_TREE)
+ return NULL_TREE;
+ else if (TREE_CODE (call) == FUNCTION_DECL)
+ return call;
+ else if (TREE_TYPE (call) && INDIRECT_TYPE_P (TREE_TYPE (call)))
+ return cp_get_fndecl_from_callee (call, /*fold=*/false);
+ else
+ return NULL_TREE;
+}
+
/* Subroutine of convert_to_void. Warn if we're discarding something with
attribute [[nodiscard]]. */
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 3e7ed98fed3..7b63304ebf3 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_template (variant);
input_location = save_loc;
if (variant)
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 4d1592ab0d2..716ee48446d 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -734,7 +734,7 @@ is_std_constant_evaluated_p (tree fn)
if (call_expr_nargs (fn) != 0)
return false;
- tree fndecl = cp_get_callee_fndecl_nofold (fn);
+ tree fndecl = cp_get_callee_fndecl_template (fn);
if (fndecl == NULL_TREE)
return false;
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: e42f342652981aa9181cc3ceb04e0eb715506764
