On 4/15/22 07:22, Jakub Jelinek wrote:
Hi!
The CONSTRUCTOR_PLACEHOLDER_BOUNDARY bit is supposed to separate
PLACEHOLDER_EXPRs that should be replaced by one object or subobjects of it
(variable, TARGET_EXPR slot, ...) from other PLACEHOLDER_EXPRs that should
be replaced by different objects or subobjects.
The bit is set when finding PLACEHOLDER_EXPRs inside of a CONSTRUCTOR, not
looking into nested CONSTRUCTOR_PLACEHOLDER_BOUNDARY ctors, and we prevent
elision of TARGET_EXPRs (through TARGET_EXPR_NO_ELIDE) whose initializer
is a CONSTRUCTOR_PLACEHOLDER_BOUNDARY ctor. The following testcase ICEs
though, we don't replace the placeholders in there at all, because
CONSTRUCTOR_PLACEHOLDER_BOUNDARY isn't set on the TARGET_EXPR_INITIAL
ctor, but on a ctor nested in such a ctor. replace_placeholders should be
run on the whole TARGET_EXPR slot.
So, the following patch fixes it by moving the CONSTRUCTOR_PLACEHOLDER_BOUNDARY
bit from nested CONSTRUCTORs to the CONSTRUCTOR containing those (but only
if it is closely nested, if there is some other tree sandwiched in between,
it doesn't do it).
Hmm, Patrick made a similar change and then reverted it for PR90996.
But it makes sense to me; when we replace placeholders, it's appropriate
to look at the whole aggregate initialization rather than the innermost
CONSTRUCTOR that has DMIs. Patrick, was there a reason that change
seemed wrong to you, or was it just unnecessary for the bug you were
working on?
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2022-04-15 Jakub Jelinek <ja...@redhat.com>
PR c++/105256
* typeck2.cc (process_init_constructor_array,
process_init_constructor_record, process_init_constructor_union): Move
CONSTRUCTOR_PLACEHOLDER_BOUNDARY flag from CONSTRUCTOR elements to the
containing CONSTRUCTOR.
* g++.dg/cpp0x/pr105256.C: New test.
--- gcc/cp/typeck2.cc.jj 2022-04-07 09:09:54.432995137 +0200
+++ gcc/cp/typeck2.cc 2022-04-14 16:02:12.438432494 +0200
@@ -1515,6 +1515,14 @@ process_init_constructor_array (tree typ
strip_array_types (TREE_TYPE (ce->value)))));
picflags |= picflag_from_initializer (ce->value);
+ /* Propagate CONSTRUCTOR_PLACEHOLDER_BOUNDARY to outer
+ CONSTRUCTOR. */
+ if (TREE_CODE (ce->value) == CONSTRUCTOR
+ && CONSTRUCTOR_PLACEHOLDER_BOUNDARY (ce->value))
+ {
+ CONSTRUCTOR_PLACEHOLDER_BOUNDARY (init) = 1;
+ CONSTRUCTOR_PLACEHOLDER_BOUNDARY (ce->value) = 0;
+ }
}
/* No more initializers. If the array is unbounded, we are done. Otherwise,
@@ -1560,6 +1568,14 @@ process_init_constructor_array (tree typ
}
picflags |= picflag_from_initializer (next);
+ /* Propagate CONSTRUCTOR_PLACEHOLDER_BOUNDARY to outer
+ CONSTRUCTOR. */
+ if (TREE_CODE (next) == CONSTRUCTOR
+ && CONSTRUCTOR_PLACEHOLDER_BOUNDARY (next))
+ {
+ CONSTRUCTOR_PLACEHOLDER_BOUNDARY (init) = 1;
+ CONSTRUCTOR_PLACEHOLDER_BOUNDARY (next) = 0;
+ }
if (len > i+1)
{
tree range = build2 (RANGE_EXPR, size_type_node,
@@ -1754,6 +1770,13 @@ process_init_constructor_record (tree ty
if (fldtype != TREE_TYPE (field))
next = cp_convert_and_check (TREE_TYPE (field), next, complain);
picflags |= picflag_from_initializer (next);
+ /* Propagate CONSTRUCTOR_PLACEHOLDER_BOUNDARY to outer CONSTRUCTOR. */
+ if (TREE_CODE (next) == CONSTRUCTOR
+ && CONSTRUCTOR_PLACEHOLDER_BOUNDARY (next))
+ {
+ CONSTRUCTOR_PLACEHOLDER_BOUNDARY (init) = 1;
+ CONSTRUCTOR_PLACEHOLDER_BOUNDARY (next) = 0;
+ }
CONSTRUCTOR_APPEND_ELT (v, field, next);
}
@@ -1894,6 +1917,14 @@ process_init_constructor_union (tree typ
ce->value = massage_init_elt (TREE_TYPE (ce->index), ce->value, nested,
flags, complain);
+ /* Propagate CONSTRUCTOR_PLACEHOLDER_BOUNDARY to outer CONSTRUCTOR. */
+ if (ce->value
+ && TREE_CODE (ce->value) == CONSTRUCTOR
+ && CONSTRUCTOR_PLACEHOLDER_BOUNDARY (ce->value))
+ {
+ CONSTRUCTOR_PLACEHOLDER_BOUNDARY (init) = 1;
+ CONSTRUCTOR_PLACEHOLDER_BOUNDARY (ce->value) = 0;
+ }
return picflag_from_initializer (ce->value);
}
--- gcc/testsuite/g++.dg/cpp0x/pr105256.C.jj 2022-04-14 16:04:30.518518875 +0200
+++ gcc/testsuite/g++.dg/cpp0x/pr105256.C 2022-04-14 16:03:53.264035175
+0200
@@ -0,0 +1,18 @@
+// PR c++/105256
+// { dg-do compile { target c++11 } }
+
+int bar (int &);
+
+struct S {
+ struct T {
+ struct U {
+ int i = bar (i);
+ } u;
+ };
+};
+
+void
+foo (S::T *p)
+{
+ *p = {};
+};
Jakub
