Re: [PATCH] c++: Fix unchecked use of CLASSTYPE_AS_BASE [PR113031]

[Jason Merrill]

On 12/15/23 19:20, Nathaniel Shead wrote:

Bootstrapped and regtested on x86_64-pc-linux-gnu with GLIBCXX_TESTSUITE_STDS=20
and RUNTESTFLAGS="--target_board=unix/-D_GLIBCXX_USE_CXX11_ABI=0".

OK, thanks.

-- >8 --

My previous patch (naively) assumed that a TREE_CODE of RECORD_TYPE or
UNION_TYPE was sufficient for optype to be considered a "class type".
However, this does not account for e.g. template type parameters of
record or union type. This patch corrects to check for CLASS_TYPE_P
before checking for as-base conversion.

        PR c++/113031

gcc/cp/ChangeLog:

        * constexpr.cc (cxx_fold_indirect_ref_1): Check for CLASS_TYPE
        before using CLASSTYPE_AS_BASE.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp0x/pr113031.C: New test.

Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
---
  gcc/cp/constexpr.cc                   |  3 ++-
  gcc/testsuite/g++.dg/cpp0x/pr113031.C | 34 +++++++++++++++++++++++++++
  2 files changed, 36 insertions(+), 1 deletion(-)
  create mode 100644 gcc/testsuite/g++.dg/cpp0x/pr113031.C

diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index e1b2d27fc36..051f73fb73f 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -5709,7 +5709,8 @@ cxx_fold_indirect_ref_1 (const constexpr_ctx *ctx, 
location_t loc, tree type,
          }

/* Handle conversion to "as base" type. */

-      if (CLASSTYPE_AS_BASE (optype) == type)
+      if (CLASS_TYPE_P (optype)
+         && CLASSTYPE_AS_BASE (optype) == type)
        return op;

/* Handle conversion to an empty base class, which is represented with a

diff --git a/gcc/testsuite/g++.dg/cpp0x/pr113031.C 
b/gcc/testsuite/g++.dg/cpp0x/pr113031.C
new file mode 100644
index 00000000000..aecdc3fc4b2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/pr113031.C
@@ -0,0 +1,34 @@
+// PR c++/113031
+// { dg-do compile }
+
+template <typename> struct variant;
+
+template <typename _Types, typename _Tp>
+variant<_Types> __variant_cast(_Tp __rhs) { return 
static_cast<variant<_Types>&>(__rhs); }
+
+template <typename _Types>
+struct _Move_assign_base : _Types {
+  void operator=(_Move_assign_base __rhs) { __variant_cast<_Types>(__rhs); }
+};
+
+template <typename _Types>
+struct variant : _Move_assign_base<_Types> {
+  void emplace() {
+    variant __tmp;
+    *this = __tmp;
+  }
+};
+
+struct _Undefined_class {
+  struct _Nocopy_types {
+    void (_Undefined_class::*_M_member_pointer)();
+  };
+  struct function : _Nocopy_types {
+    struct optional {
+      void test03() {
+        variant<function> v;
+        v.emplace();
+      }
+    };
+  };
+};