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c++: Make sure fold_sizeof_expr returns the correct type [PR117775]

Message ID 0102019378575fe9-366c9ac9-4829-4fb2-b6d5-f34501a9df8a-000000@eu-west-1.amazonses.com
State New
Headers
Series c++: Make sure fold_sizeof_expr returns the correct type [PR117775] |

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Commit Message

Simon Martin Nov. 29, 2024, 2:33 p.m. UTC 
  We currently ICE upon the following code, that is valid under
-Wno-pointer-arith:

=== cut here ===
int main() {
  decltype( [](auto) { return sizeof(void); } ) x;
  return x.operator()(0);
}
=== cut here ===

The problem is that "fold_sizeof_expr (sizeof(void))" returns
size_one_node, that has a different TREE_TYPE from that of the sizeof
expression, which later triggers an assert in cxx_eval_store_expression.

This patch makes sure that fold_sizeof_expr always returns a tree with
the type requested.

Successfully tested on x86_64-pc-linux-gnu.

	PR c++/117775

gcc/cp/ChangeLog:

	* decl.cc (fold_sizeof_expr): Make sure the folded result has
	the requested TREE_TYPE.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/constexpr-117775.C: New test.

---
 gcc/cp/decl.cc                                |  1 +
 gcc/testsuite/g++.dg/cpp2a/constexpr-117775.C | 13 +++++++++++++
 2 files changed, 14 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/constexpr-117775.C
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Patch

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 80485f0a428..fbe1407a2d2 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -11686,6 +11686,7 @@  fold_sizeof_expr (tree t)
 				    false, false);
   if (r == error_mark_node)
     r = size_one_node;
+  r = cp_fold_convert (TREE_TYPE (t), r);
   return r;
 }
 
diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-117775.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-117775.C
new file mode 100644
index 00000000000..59fc0d332b9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-117775.C
@@ -0,0 +1,13 @@ 
+// PR c++/117775
+// Check that we don't ICE and have sizeof(void)==1 under -Wno-pointer-arith
+// { dg-do run { target c++20 } }
+// { dg-additional-options "-Wno-pointer-arith" }
+
+int main() {
+  struct why :
+    decltype( [](auto) {
+		return sizeof(void);
+	      })
+  {} x;
+  return 1 - x.operator()(0);
+}