* C++ PATCH for c++/80829, ICE with constexpr copy of base
@ 2017-06-19 20:52 Jason Merrill
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From: Jason Merrill @ 2017-06-19 20:52 UTC (permalink / raw)
To: gcc-patches List
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The constexpr code uses the CONSTRUCTOR_NO_IMPLICIT_ZERO flag to track
partially-initialized aggregates, but we were failing to clear it on
base subobjects.
Tested x86_64-pc-linux-gnu, applying to trunk and 7.
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commit 2e3142bcd6fde9f9ac22928718e55584a6255286
Author: Jason Merrill <jason@redhat.com>
Date: Mon Jun 19 15:15:14 2017 -0400
PR c++/80829 - ICE with constexpr copy of base subobject.
* constexpr.c (clear_no_implicit_zero): New.
(cxx_eval_call_expression): Call it.
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 569a247..5a57452 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -1394,6 +1394,21 @@ cxx_eval_internal_function (const constexpr_ctx *ctx, tree t,
return t;
}
+/* Clean CONSTRUCTOR_NO_IMPLICIT_ZERO from CTOR and its sub-aggregates. */
+
+static void
+clear_no_implicit_zero (tree ctor)
+{
+ if (CONSTRUCTOR_NO_IMPLICIT_ZERO (ctor))
+ {
+ CONSTRUCTOR_NO_IMPLICIT_ZERO (ctor) = false;
+ tree elt; unsigned HOST_WIDE_INT idx;
+ FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (ctor), idx, elt)
+ if (TREE_CODE (elt) == CONSTRUCTOR)
+ clear_no_implicit_zero (elt);
+ }
+}
+
/* Subroutine of cxx_eval_constant_expression.
Evaluate the call expression tree T in the context of OLD_CALL expression
evaluation. */
@@ -1697,7 +1712,7 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
/* The result of a constexpr function must be completely initialized. */
if (TREE_CODE (result) == CONSTRUCTOR)
- CONSTRUCTOR_NO_IMPLICIT_ZERO (result) = false;
+ clear_no_implicit_zero (result);
pop_cx_call_context ();
return unshare_constructor (result);
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-base5.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-base5.C
new file mode 100644
index 0000000..84700bc
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-base5.C
@@ -0,0 +1,15 @@
+// PR c++/80829
+// { dg-do compile { target c++11 } }
+
+struct A {
+ constexpr A(int a) : _a(a) {}
+ int _a;
+};
+
+struct B : public A {
+ constexpr B(int a) : A(a) {}
+};
+
+int main() {
+ constexpr A a = B(10);
+}
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