[gcc r15-6308] c++: ICE initializing array of aggrs [PR117985]

[Marek Polacek via Gcc-cvs]

https://gcc.gnu.org/g:40e5636e086e51f5908a1a01be9cba2218dc26d8

commit r15-6308-g40e5636e086e51f5908a1a01be9cba2218dc26d8
Author: Marek Polacek <pola...@redhat.com>
Date:   Thu Dec 12 14:56:07 2024 -0500

    c++: ICE initializing array of aggrs [PR117985]
    
    This crash started with my r12-7803 but I believe the problem lies
    elsewhere.
    
    build_vec_init has cleanup_flags whose purpose is -- if I grok this
    correctly -- to avoid destructing an object multiple times.  Let's
    say we are initializing an array of A.  Then we might end up in
    a scenario similar to initlist-eh1.C:
    
      try
        {
          call A::A in a loop
          // #0
          try
            {
              call a fn using the array
            }
          finally
            {
              // #1
              call A::~A in a loop
            }
        }
      catch
        {
          // #2
          call A::~A in a loop
        }
    
    cleanup_flags makes us emit a statement like
    
      D.3048 = 2;
    
    at #0 to disable performing the cleanup at #2, since #1 will take
    care of the destruction of the array.
    
    But if we are not emitting the loop because we can use a constant
    initializer (and use a single { a, b, ...}), we shouldn't generate
    the statement resetting the iterator to its initial value.  Otherwise
    we crash in gimplify_var_or_parm_decl because it gets the stray decl
    D.3048.
    
            PR c++/117985
    
    gcc/cp/ChangeLog:
    
            * init.cc (build_vec_init): Pop CLEANUP_FLAGS if we're not
            generating the loop.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp0x/initlist-array23.C: New test.
            * g++.dg/cpp0x/initlist-array24.C: New test.

Diff:
---
 gcc/cp/init.cc                                |  9 +++++++++
 gcc/testsuite/g++.dg/cpp0x/initlist-array23.C | 28 +++++++++++++++++++++++++++
 gcc/testsuite/g++.dg/cpp0x/initlist-array24.C | 27 ++++++++++++++++++++++++++
 3 files changed, 64 insertions(+)

diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
index ae516407c927..7dcc1152c720 100644
--- a/gcc/cp/init.cc
+++ b/gcc/cp/init.cc
@@ -5109,6 +5109,15 @@ build_vec_init (tree base, tree maxindex, tree init,
     {
       if (!saw_non_const)
        {
+         /* If we're not generating the loop, we don't need to reset the
+            iterator.  */
+         if (cleanup_flags
+             && !vec_safe_is_empty (*cleanup_flags))
+           {
+             auto l = (*cleanup_flags)->last ();
+             gcc_assert (TREE_PURPOSE (l) == iterator);
+             (*cleanup_flags)->pop ();
+           }
          tree const_init = build_constructor (atype, const_vec);
          return build2 (INIT_EXPR, atype, obase, const_init);
        }
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-array23.C 
b/gcc/testsuite/g++.dg/cpp0x/initlist-array23.C
new file mode 100644
index 000000000000..cda2afb9fccc
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist-array23.C
@@ -0,0 +1,28 @@
+// PR c++/117985
+// { dg-do compile { target c++11 } }
+
+struct _Vector_impl {
+  constexpr
+    _Vector_impl() {}
+};
+struct _Vector_base {
+  ~_Vector_base();
+  _Vector_impl _M_impl;
+};
+struct vector : private _Vector_base {};
+struct string {
+  string();
+};
+struct VEC {
+  vector pane{};
+};
+struct FOO {
+  VEC screen[1]{};
+  string debug_name;
+};
+
+int
+main ()
+{
+  FOO{};
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-array24.C 
b/gcc/testsuite/g++.dg/cpp0x/initlist-array24.C
new file mode 100644
index 000000000000..7dda00d5c0b8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist-array24.C
@@ -0,0 +1,27 @@
+// PR c++/117985
+// { dg-do compile { target c++20 } }
+
+struct _Vector_impl {
+  constexpr _Vector_impl() {}
+};
+struct _Vector_base {
+  constexpr ~_Vector_base() {}
+  _Vector_impl _M_impl;
+};
+struct vector : private _Vector_base {};
+struct string {
+  string();
+};
+struct VEC {
+  vector pane{};
+};
+struct FOO {
+  VEC screen[1]{};
+  string debug_name;
+};
+
+int
+main ()
+{
+  FOO{};
+}