[gcc(refs/users/meissner/heads/ieee)] c++: Fix crash in gimplifier with paren init of aggregates [PR94155]

[Michael Meissner <meissner@gcc.gnu.org>]

https://gcc.gnu.org/g:f84aded848f6fdd2704c9376263c6d1aee6bb0ca

commit f84aded848f6fdd2704c9376263c6d1aee6bb0ca
Author: Marek Polacek <polacek@redhat.com>
Date:   Mon Mar 30 15:49:17 2020 -0400

    c++: Fix crash in gimplifier with paren init of aggregates [PR94155]
    
    Here we crash in the gimplifier because gimplify_init_ctor_eval doesn't
    expect null indexes for a constructor:
    
          /* ??? Here's to hoping the front end fills in all of the indices,
             so we don't have to figure out what's missing ourselves.  */
          gcc_assert (purpose);
    
    The indexes weren't filled because we never called reshape_init: for
    a constructor that represents parenthesized initialization of an
    aggregate we don't allow brace elision or designated initializers.
    
            PR c++/94155 - crash in gimplifier with paren init of aggregates.
            * init.c (build_vec_init): Fill in indexes.
    
            * g++.dg/cpp2a/paren-init22.C: New test.

Diff:
---
 gcc/cp/ChangeLog                          |  6 ++++++
 gcc/cp/init.c                             |  2 ++
 gcc/testsuite/ChangeLog                   |  5 +++++
 gcc/testsuite/g++.dg/cpp2a/paren-init22.C | 15 +++++++++++++++
 4 files changed, 28 insertions(+)

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index a382235d7cc..fc75879d14f 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2020-04-04  Marek Polacek  <polacek@redhat.com>
+	    Jason Merrill  <jason@redhat.com>
+
+	PR c++/94155 - crash in gimplifier with paren init of aggregates.
+	* init.c (build_vec_init): Fill in indexes.
+
 2020-04-04  Jason Merrill  <jason@redhat.com>
 
 	PR c++/91377
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 27623cf4db1..ea95a3bc910 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -4438,6 +4438,8 @@ build_vec_init (tree base, tree maxindex, tree init,
 	    errors = true;
 	  if (try_const)
 	    {
+	      if (!field)
+		field = size_int (idx);
 	      tree e = maybe_constant_init (one_init);
 	      if (reduced_constant_expression_p (e))
 		{
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 88bab5d3d19..29830633d79 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-04-04  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/94155 - crash in gimplifier with paren init of aggregates.
+	* g++.dg/cpp2a/paren-init22.C: New test.
+
 2020-04-05  Iain Sandoe  <iain@sandoe.co.uk>
 
 	* g++.dg/coroutines/torture/co-await-14-template-traits.C: Rename...
diff --git a/gcc/testsuite/g++.dg/cpp2a/paren-init22.C b/gcc/testsuite/g++.dg/cpp2a/paren-init22.C
new file mode 100644
index 00000000000..1b2959e7731
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/paren-init22.C
@@ -0,0 +1,15 @@
+// PR c++/94155 - crash in gimplifier with paren init of aggregates.
+// { dg-do compile { target c++2a } }
+
+struct S { int i, j; };
+
+struct A {
+  S s;
+  constexpr A(S e) : s(e) {}
+};
+
+void
+f()
+{
+  A g[1]({{1, 1}});
+}