Hi!
The testcase has UB at runtime, placement new shouldn't construct
an object with certain alignment requirements into an unaligned buffer.
Discussed on IRC, tested on x86_64-linux -m32/-m64, committed to trunk.
2022-03-30 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/80334
PR target/102772
* g++.dg/torture/pr80334.C: Change from dg-do run to dg-do compile.
--- gcc/testsuite/g++.dg/torture/pr80334.C.jj 2020-01-12 11:54:37.268400509
+0100
+++ gcc/testsuite/g++.dg/torture/pr80334.C 2022-03-30 15:56:54.259507802
+0200
@@ -1,4 +1,8 @@
-// { dg-do run }
+// This used to be dg-do run testcase, but it is invalid at runtime:
+// trying to do a placement new of A which is 16-byte sized and aligned
+// into a 16-byte buffer at offset 17 bytes from 16-byte aligned address
+// is UB.
+// { dg-do compile }
struct A { alignas(16) char c; };
struct B { A unpacked; char d; } __attribute__((packed));
Jakub
