[gcc r12-7744] c++: initialized array of vla [PR58646]

[Jason Merrill <jason@gcc.gnu.org>]

https://gcc.gnu.org/g:c65bd532e225996cc9c5b75355d2cb648d0bcfc5

commit r12-7744-gc65bd532e225996cc9c5b75355d2cb648d0bcfc5
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Mar 21 17:48:01 2022 -0400

    c++: initialized array of vla [PR58646]
    
    We went into build_vec_init because we're dealing with a VLA, but then
    build_vec_init thought it was safe to just build an INIT_EXPR because the
    outer dimension is constant.  Nope.
    
            PR c++/58646
    
    gcc/cp/ChangeLog:
    
            * init.cc (build_vec_init): Check for vla element type.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/ext/vla24.C: New test.

Diff:
---
 gcc/cp/init.cc                   | 1 +
 gcc/testsuite/g++.dg/ext/vla24.C | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
index 7575597c8fd..08767679dd4 100644
--- a/gcc/cp/init.cc
+++ b/gcc/cp/init.cc
@@ -4395,6 +4395,7 @@ build_vec_init (tree base, tree maxindex, tree init,
   if (init
       && TREE_CODE (atype) == ARRAY_TYPE
       && TREE_CONSTANT (maxindex)
+      && !vla_type_p (type)
       && (from_array == 2
 	  ? vec_copy_assign_is_trivial (inner_elt_type, init)
 	  : !TYPE_NEEDS_CONSTRUCTING (type))
diff --git a/gcc/testsuite/g++.dg/ext/vla24.C b/gcc/testsuite/g++.dg/ext/vla24.C
new file mode 100644
index 00000000000..0a99c003ffb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/vla24.C
@@ -0,0 +1,7 @@
+// PR c++/58646
+// { dg-additional-options -Wno-vla }
+
+void foo(int n)
+{
+  int a[2][n] = {};
+}