* [pushed] c++: no clobber for C++20 destroying delete [PR91859]
@ 2021-06-01 15:40 Jason Merrill
0 siblings, 0 replies; only message in thread
From: Jason Merrill @ 2021-06-01 15:40 UTC (permalink / raw)
To: gcc-patches
Before C++20 added destroying operator delete, by the time we called
operator delete for a pointer, the object would already be gone. But that
isn't true for destroying delete. Since the optimizers' assumptions about
operator delete are based on either DECL_IS_REPLACEABLE_OPERATOR (which
already is not set) or CALL_FROM_NEW_OR_DELETE_P, let's avoid setting the
latter flag in this case.
Tested x86_64-pc-linux-gnu, applying to trunk.
PR c++/91859
gcc/ChangeLog:
* tree.h (CALL_FROM_NEW_OR_DELETE_P): Adjust comment.
gcc/cp/ChangeLog:
* call.c (build_op_delete_call): Don't set CALL_FROM_NEW_OR_DELETE_P
for destroying delete.
* init.c (build_delete): Don't clobber before destroying delete.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/destroying-delete5.C: New test.
---
gcc/tree.h | 2 +-
gcc/cp/call.c | 4 ++-
gcc/cp/init.c | 5 ++-
.../g++.dg/cpp2a/destroying-delete5.C | 36 +++++++++++++++++++
4 files changed, 44 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/destroying-delete5.C
diff --git a/gcc/tree.h b/gcc/tree.h
index 260a3ae6c83..62b2de46479 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -937,7 +937,7 @@ extern void omp_clause_range_check_failed (const_tree, const char *, int,
/* In a CALL_EXPR, if the function being called is DECL_IS_OPERATOR_NEW_P or
DECL_IS_OPERATOR_DELETE_P, true for allocator calls from C++ new or delete
- expressions. */
+ expressions. Not set for C++20 destroying delete operators. */
#define CALL_FROM_NEW_OR_DELETE_P(NODE) \
(CALL_EXPR_CHECK (NODE)->base.protected_flag)
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index bf524b50bc4..90192b1b8aa 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -7206,8 +7206,10 @@ build_op_delete_call (enum tree_code code, tree addr, tree size,
treat that as an implicit delete-expression. This is also called for
the delete if the constructor throws in a new-expression, and for a
deleting destructor (which implements a delete-expression). */
+ /* But leave this flag off for destroying delete to avoid wrong
+ assumptions in the optimizers. */
tree call = extract_call_expr (ret);
- if (TREE_CODE (call) == CALL_EXPR)
+ if (TREE_CODE (call) == CALL_EXPR && !destroying_delete_p (fn))
CALL_FROM_NEW_OR_DELETE_P (call) = 1;
return ret;
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index a85f4d50750..04d495807ef 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -4881,7 +4881,10 @@ build_delete (location_t loc, tree otype, tree addr,
complain);
}
- if (!destroying_delete && type_build_dtor_call (type))
+ if (destroying_delete)
+ /* The operator delete will call the destructor. */
+ expr = addr;
+ else if (type_build_dtor_call (type))
expr = build_dtor_call (cp_build_fold_indirect_ref (addr),
auto_delete, flags, complain);
else
diff --git a/gcc/testsuite/g++.dg/cpp2a/destroying-delete5.C b/gcc/testsuite/g++.dg/cpp2a/destroying-delete5.C
new file mode 100644
index 00000000000..553c964b9e9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/destroying-delete5.C
@@ -0,0 +1,36 @@
+// PR c++/91859
+// { dg-do run { target c++20 } }
+// { dg-additional-options -O2 }
+
+#include <cstdlib>
+#include <new>
+
+struct Expression {
+ int i = 0;
+ void *operator new(std::size_t);
+ void operator delete(Expression *, std::destroying_delete_t);
+};
+
+void * Expression::operator new(std::size_t sz)
+{
+ return std::malloc(sz);
+}
+
+int i;
+
+void Expression::operator delete(Expression *p, std::destroying_delete_t)
+{
+ Expression * e = p;
+ ::i = e->i;
+ p->~Expression();
+ std::free(p);
+}
+
+int main()
+{
+ auto p = new Expression();
+ p->i = 1;
+ delete p;
+ if (i != 1)
+ __builtin_abort();
+}
--
2.27.0
^ permalink raw reply [flat|nested] only message in thread
only message in thread, other threads:[~2021-06-01 15:41 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-06-01 15:40 [pushed] c++: no clobber for C++20 destroying delete [PR91859] Jason Merrill
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).