On 2/2/23 19:28, Marek Polacek wrote:
Here we're attempting to evaluate a PTRMEM_CST in a class that hasn't
been completed yet, but that doesn't work:
/* We can't lower this until the class is complete. */
if (!COMPLETE_TYPE_P (DECL_CONTEXT (member)))
return cst;
and then this unlowered PTRMEM_CST is used as EXPR in
tree op1 = build_nop (ptrdiff_type_node, expr);
and we crash in a subsequent cp_fold_convert which gets type=ptrdiff_type_node,
expr=PTRMEM_CST and does
else if (TREE_CODE (expr) == PTRMEM_CST
&& same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
PTRMEM_CST_CLASS (expr)))
where TYPE_PTRMEM_CLASS_TYPE (type) is going to crash since the type
is ptrdiff_type_node. We could just add a TYPE_PTRMEM_P check before
accessing TYPE_PTRMEM_CLASS_TYPE but I think it's nicer to explain why
we couldn't evaluate the expression.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR c++/107574
gcc/cp/ChangeLog:
* constexpr.cc (cxx_eval_constant_expression): Emit an error when
a PTRMEM_CST cannot be evaluated.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/ptrmem-cst1.C: New test.
---
gcc/cp/constexpr.cc | 9 +++++++++
gcc/testsuite/g++.dg/cpp0x/ptrmem-cst1.C | 11 +++++++++++
2 files changed, 20 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/ptrmem-cst1.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 5b31f9c27d1..2c03988b097 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -7691,6 +7691,15 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx,
tree t,
if (!same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE
(op))
&& !can_convert_qual (type, op))
op = cplus_expand_constant (op);
+ if (TREE_CODE (op) == PTRMEM_CST && !TYPE_PTRMEM_P (type))
+ {
+ if (!ctx->quiet)
+ error_at (loc, "%qE is not a constant expression when the "
+ "class %qT is still incomplete", op,
+ PTRMEM_CST_CLASS (op));
+ *non_constant_p = true;
+ return t;
+ }
Hmm, maybe handle this a few lines higher, in this existing if:
if (TREE_CODE (op) == PTRMEM_CST && !TYPE_PTRMEM_P (type))
op = cplus_expand_constant (op);
? OK with that change.
