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* [gcc r13-6400] c++: can't eval PTRMEM_CST in incomplete class [PR107574]
@ 2023-03-01 23:33 Marek Polacek
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From: Marek Polacek @ 2023-03-01 23:33 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:de81e06273c613d7e06cbe2c8d9e72826c638056
commit r13-6400-gde81e06273c613d7e06cbe2c8d9e72826c638056
Author: Marek Polacek <polacek@redhat.com>
Date: Thu Feb 2 18:15:37 2023 -0500
c++: can't eval PTRMEM_CST in incomplete class [PR107574]
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.
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.
Diff:
---
gcc/cp/constexpr.cc | 13 ++++++++++++-
gcc/testsuite/g++.dg/cpp0x/ptrmem-cst1.C | 11 +++++++++++
2 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index bcae1cbd973..0770cdcd768 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -7662,7 +7662,18 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
}
if (TREE_CODE (op) == PTRMEM_CST && !TYPE_PTRMEM_P (type))
- op = cplus_expand_constant (op);
+ {
+ op = cplus_expand_constant (op);
+ if (TREE_CODE (op) == PTRMEM_CST)
+ {
+ 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;
+ }
+ }
if (TREE_CODE (op) == PTRMEM_CST && tcode == NOP_EXPR)
{
diff --git a/gcc/testsuite/g++.dg/cpp0x/ptrmem-cst1.C b/gcc/testsuite/g++.dg/cpp0x/ptrmem-cst1.C
new file mode 100644
index 00000000000..0d6a6b6445d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/ptrmem-cst1.C
@@ -0,0 +1,11 @@
+// PR c++/107574
+// { dg-do compile { target c++11 } }
+
+struct A { int i; };
+struct B:A { int j; };
+struct C:B {
+ int k;
+ static_assert((int B::*) &C::k, ""); // { dg-error "non-constant|still incomplete" }
+};
+
+static_assert((int B::*) &C::k, "");
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