From 25056bdf94d5f3e66bef039702f7fae799ef16b9 Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Wed, 18 Nov 2020 22:49:59 -0500
Subject: [PATCH] c++: Fix crash with broken deduction from {} [PR97895]
Unfortunately, the otherwise beautiful
for (constructor_elt &elt : *CONSTRUCTOR_ELTS (init))
is not immune to an empty constructor, so we have to check
CONSTRUCTOR_ELTS first.
gcc/cp/ChangeLog:
PR c++/97895
* pt.c (do_auto_deduction): Don't crash when the constructor has
zero elements.
gcc/testsuite/ChangeLog:
PR c++/97895
* g++.dg/cpp0x/auto54.C: New test.
---
gcc/cp/pt.c | 11 +++++++----
gcc/testsuite/g++.dg/cpp0x/auto54.C | 10 ++++++++++
2 files changed, 17 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/auto54.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 1babf833d321..a1b6631d6915 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -29250,10 +29250,13 @@ do_auto_deduction (tree type, tree init, tree auto_node,
return error_mark_node;
if (BRACE_ENCLOSED_INITIALIZER_P (init))
- /* We don't recurse here because we can't deduce from a nested
- initializer_list. */
- for (constructor_elt &elt : *CONSTRUCTOR_ELTS (init))
- elt.value = resolve_nondeduced_context (elt.value, complain);
+ {
+ /* We don't recurse here because we can't deduce from a nested
+ initializer_list. */
+ if (CONSTRUCTOR_ELTS (init))
+ for (constructor_elt &elt : *CONSTRUCTOR_ELTS (init))
+ elt.value = resolve_nondeduced_context (elt.value, complain);
+ }
else
init = resolve_nondeduced_context (init, complain);
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto54.C b/gcc/testsuite/g++.dg/cpp0x/auto54.C
new file mode 100644
index 000000000000..0c1815a99bce
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/auto54.C
@@ -0,0 +1,10 @@
+// PR c++/97895
+// { dg-do compile { target c++11 } }
+
+namespace std {
+ template<typename T> struct initializer_list {
+ const T *ptr;
+ decltype(sizeof 0) n;
+ };
+ auto a = {}; // { dg-error "unable to deduce" }
+}
--
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