On 9/1/23 20:00, Marek Polacek wrote:
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
When verify_constant complains, it's pretty terse. Consider
void test ()
{
constexpr int i = 42;
constexpr const int *p = &i;
}
where it says "'& i' is not a constant expression". OK, but why?
With this patch, we say:
b.C:5:28: error: '& i' is not a constant expression
5 | constexpr const int *p = &i;
| ^~
b.C:5:28: note: pointer to 'i' is not a constant expression
b.C:4:17: note: address of non-static constexpr variable 'i' may differ on each
invocation of the enclosing function; add 'static' to give it a constant address
4 | constexpr int i = 42;
| ^
| static
which brings g++ on par with clang++.
gcc/cp/ChangeLog:
* constexpr.cc (verify_constant_explain_r): New.
(verify_constant): Call it.
gcc/testsuite/ChangeLog:
* g++.dg/diagnostic/constexpr3.C: New test.
---
gcc/cp/constexpr.cc | 56 +++++++++++++++++++-
gcc/testsuite/g++.dg/diagnostic/constexpr3.C | 32 +++++++++++
2 files changed, 87 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/diagnostic/constexpr3.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 8bd5c4a47f8..6d5aed82377 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -3381,6 +3381,54 @@ ok:
}
}
+/* *TP was not deemed constant by reduced_constant_expression_p. Explain
+ why and suggest what could be done about it. */
+
+static tree
+verify_constant_explain_r (tree *tp, int *, void *)
+{
+ bool ref_p = false;
I think you'll want something along the lines of
/* No need to look into types or unevaluated operands. */
if (TYPE_P (init) || unevaluated_p (code))
{
*walk_subtrees = false;
return NULL_TREE;
}
(from find_uninit_fields_r).
OK with that change.
Jason
