On Mon, 10 Feb 2020, Jason Merrill wrote:
> On 2/10/20 2:20 PM, Patrick Palka wrote:
> > This patch fixes two issues with return type deduction in the presence of an
> > abbreviated function template.
> >
> > The first issue (PR 69448) is that if a placeholder auto return type
> > contains
> > any modifiers such as & or *, then the abbreviated-function-template
> > compensation in splice_late_return_type does not get performed for the
> > underlying auto node, leading to incorrect return type deduction. This
> > happens
> > because splice_late_return_type checks for a placeholder auto with is_auto,
> > which does not look through modifiers. This patch replaces the use of
> > is_auto
> > with find_type_usage, but it first refactors find_type_usage to return a
> > pointer
> > to the matched tree so that we next subsequently replace it.
> >
> > The second issue (PR 80471) is that the AUTO_IS_DECLTYPE flag is not being
> > preserved in splice_late_return_type when compensating for an abbreviated
> > function template, leading to us treating a decltype(auto) return type as if
> > it
> > was an auto return type. Fixed by propagating AUTO_IS_DECLTYPE. The test
> > for
> > PR 80471 is adjusted to expect the correct behavior.
>
> The comment in make_constrained_decltype_auto suggests that we should set
> AUTO_IS_DECLTYPE in make_auto_1 if name == decltype_auto_identifier; then
> callers won't need to worry about it.
Updated the patch to make_auto_1 to set AUTO_IS_DECLTYPE when
appropriate, and adjusted callers accordingly. Now make_auto_1 is the
only place where we set AUTO_IS_DECLTYPE.
>
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, is this OK to commit?
> >
> > gcc/cp/ChangeLog:
> >
> > PR c++/69448
> > PR c++/80471
> > * type-utils.h (find_type_usage): Refactor to take a tree * and to
> > return a tree *, and update documentation accordingly.
> > * pt.c (splice_late_return_type): Use find_type_usage to find and
> > replace a possibly nested auto node. Preserve the AUTO_IS_DECLTYPE
> > flag when replacing the node.
> > (type_uses_auto): Adjust the call to find_type_usage.
> >
> > gcc/testsuite/ChangeLog:
> >
> > PR c++/69448
> > PR c++/80471
> > * g++.dg/concepts/abbrev3.C: New test.
> > * g++.dg/cpp2a/concepts-pr80471.C: Adjust a static_assert to expect
> > the
> > correct behavior.
> > ---
> > gcc/cp/pt.c | 26 ++++++++++++-------
> > gcc/cp/type-utils.h | 26 +++++++++----------
> > gcc/testsuite/g++.dg/concepts/abbrev3.C | 11 ++++++++
> > gcc/testsuite/g++.dg/cpp2a/concepts-pr80471.C | 2 +-
> > 4 files changed, 41 insertions(+), 24 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/concepts/abbrev3.C
> >
> > diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
> > index 2fb52caa5d4..c83aaa7c7e1 100644
> > --- a/gcc/cp/pt.c
> > +++ b/gcc/cp/pt.c
> > @@ -28904,17 +28904,21 @@ do_auto_deduction (tree type, tree init, tree
> > auto_node,
> > tree
> > splice_late_return_type (tree type, tree late_return_type)
> > {
> > - if (is_auto (type))
> > - {
> > - if (late_return_type)
> > - return late_return_type;
> > + if (is_auto (type) && late_return_type)
> > + return late_return_type;
>
> It occurs to me that we could just check late_return_type here, maybe change
> the is_auto test to an assert.
Done -- I had to add a seen_error test to the assert to accomodate error
recovery and also adjust a dg-error directive in g++.dg/cpp0x/auto9.C.
Does this version look OK after testing?
-- >8 --
gcc/cp/ChangeLog:
PR c++/69448
PR c++/80471
* type-utils.h (find_type_usage): Refactor to take a tree * and to
return a tree *, and update documentation accordingly.
* pt.c (make_auto_1): Set AUTO_IS_DECLTYPE when building a
decltype(auto) node.
(make_constrained_decltype_auto): No need to explicitly set
AUTO_IS_DECLTYPE anymore.
(splice_late_return_type): Use find_type_usage to find and
replace a possibly nested auto node instead of using is_auto.
Check test for is_auto into an assert when deciding whether
to late_return_type.
(type_uses_auto): Adjust the call to find_type_usage.
* parser.c (cp_parser_decltype): No need to explicitly set
AUTO_IS_DECLTYPE anymore.
gcc/libcc1/ChangeLog:
* libcp1plugin.cc (plugin_get_expr_type): No need to explicitly set
AUTO_IS_DECLTYPE anymore.
gcc/testsuite/ChangeLog:
PR c++/69448
PR c++/80471
* g++.dg/concepts/abbrev3.C: New test.
* g++.dg/cpp2a/concepts-pr80471.C: Adjust a static_assert to expect the
correct behavior.
* g++.dg/cpp0x/auto9.C: Adjust a dg-error directive.
---
gcc/cp/parser.c | 7 ++---
gcc/cp/pt.c | 21 +++++++++------
gcc/cp/type-utils.h | 26 +++++++++----------
gcc/testsuite/g++.dg/concepts/abbrev3.C | 11 ++++++++
gcc/testsuite/g++.dg/cpp0x/auto9.C | 2 +-
gcc/testsuite/g++.dg/cpp2a/concepts-pr80471.C | 2 +-
libcc1/libcp1plugin.cc | 5 +---
7 files changed, 42 insertions(+), 32 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/concepts/abbrev3.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index d4c9523289f..640affd8368 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -14901,11 +14901,8 @@ cp_parser_decltype (cp_parser *parser)
}
if (!expr)
- {
- /* Build auto. */
- expr = make_decltype_auto ();
- AUTO_IS_DECLTYPE (expr) = true;
- }
+ /* Build auto. */
+ expr = make_decltype_auto ();
else
expr = finish_decltype_type (expr, id_expression_or_member_access_p,
tf_warning_or_error);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 01bade85cdf..e1c832c7035 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -27539,6 +27539,8 @@ make_auto_1 (tree name, bool set_canonical)
TYPE_CANONICAL (au) = canonical_type_parameter (au);
DECL_ARTIFICIAL (TYPE_NAME (au)) = 1;
SET_DECL_TEMPLATE_PARM_P (TYPE_NAME (au));
+ if (name == decltype_auto_identifier)
+ AUTO_IS_DECLTYPE (au) = true;
return au;
}
@@ -27616,8 +27618,6 @@ tree
make_constrained_decltype_auto (tree con, tree args)
{
tree type = make_auto_1 (decltype_auto_identifier, false);
- /* FIXME: I don't know why this isn't done in make_auto_1. */
- AUTO_IS_DECLTYPE (type) = true;
return make_constrained_placeholder_type (type, con, args);
}
@@ -28930,17 +28930,20 @@ do_auto_deduction (tree type, tree init, tree
auto_node,
tree
splice_late_return_type (tree type, tree late_return_type)
{
- if (is_auto (type))
+ if (late_return_type)
{
- if (late_return_type)
- return late_return_type;
+ gcc_assert (is_auto (type) || seen_error ());
+ return late_return_type;
+ }
- tree idx = get_template_parm_index (type);
+ if (tree *auto_node = find_type_usage (&type, is_auto))
+ {
+ tree idx = get_template_parm_index (*auto_node);
if (TEMPLATE_PARM_LEVEL (idx) <= processing_template_decl)
/* In an abbreviated function template we didn't know we were dealing
with a function template when we saw the auto return type, so update
it to have the correct level. */
- return make_auto_1 (TYPE_IDENTIFIER (type), true);
+ *auto_node = make_auto_1 (TYPE_IDENTIFIER (*auto_node), true);
}
return type;
}
@@ -28986,8 +28989,10 @@ type_uses_auto (tree type)
else
return NULL_TREE;
}
+ else if (tree *tp = find_type_usage (&type, is_auto))
+ return *tp;
else
- return find_type_usage (type, is_auto);
+ return NULL_TREE;
}
/* Report ill-formed occurrences of auto types in ARGUMENTS. If
diff --git a/gcc/cp/type-utils.h b/gcc/cp/type-utils.h
index 680b2497a36..4ad0d822119 100644
--- a/gcc/cp/type-utils.h
+++ b/gcc/cp/type-utils.h
@@ -20,36 +20,36 @@ along with GCC; see the file COPYING3. If not see
#ifndef GCC_CP_TYPE_UTILS_H
#define GCC_CP_TYPE_UTILS_H
-/* Returns the first tree within T that is directly matched by PRED. T may be
a
- type or PARM_DECL and is incrementally decomposed toward its type-specifier
- until a match is found. NULL_TREE is returned if PRED does not match any
- part of T.
+/* Returns a pointer to the first tree within *TP that is directly matched by
+ PRED. *TP may be a type or PARM_DECL and is incrementally decomposed toward
+ its type-specifier until a match is found. NULL is returned if PRED does
not
+ match any part of *TP.
- This is primarily intended for detecting whether T uses `auto' or a concept
+ This is primarily intended for detecting whether *TP uses `auto' or a
concept
identifier. Since either of these can only appear as a type-specifier for
the declaration in question, only top-level qualifications are traversed;
find_type_usage does not look through the whole type. */
-inline tree
-find_type_usage (tree t, bool (*pred) (const_tree))
+inline tree *
+find_type_usage (tree *tp, bool (*pred) (const_tree))
{
- enum tree_code code;
+ tree t = *tp;
if (pred (t))
- return t;
+ return tp;
- code = TREE_CODE (t);
+ enum tree_code code = TREE_CODE (t);
if (code == POINTER_TYPE || code == REFERENCE_TYPE
|| code == PARM_DECL || code == OFFSET_TYPE
|| code == FUNCTION_TYPE || code == METHOD_TYPE
|| code == ARRAY_TYPE)
- return find_type_usage (TREE_TYPE (t), pred);
+ return find_type_usage (&TREE_TYPE (t), pred);
if (TYPE_PTRMEMFUNC_P (t))
return find_type_usage
- (TREE_TYPE (TYPE_PTRMEMFUNC_FN_TYPE (t)), pred);
+ (&TREE_TYPE (TYPE_PTRMEMFUNC_FN_TYPE (t)), pred);
- return NULL_TREE;
+ return NULL;
}
#endif // GCC_CP_TYPE_UTILS_H
diff --git a/gcc/testsuite/g++.dg/concepts/abbrev3.C
b/gcc/testsuite/g++.dg/concepts/abbrev3.C
new file mode 100644
index 00000000000..ba2a648156e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/abbrev3.C
@@ -0,0 +1,11 @@
+// PR c++/69448
+// { dg-do compile { target c++14 } }
+// { dg-additional-options "-fconcepts" }
+
+long x;
+
+auto& f(auto) { return x; }
+auto* g(auto) { return &x; }
+
+long& r = f(1);
+long* p = g(1);
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto9.C
b/gcc/testsuite/g++.dg/cpp0x/auto9.C
index 8d77b0b3667..a3f9be521d6 100644
--- a/gcc/testsuite/g++.dg/cpp0x/auto9.C
+++ b/gcc/testsuite/g++.dg/cpp0x/auto9.C
@@ -22,7 +22,7 @@ struct A
struct A2
{
operator auto () -> int; // { dg-error "invalid use
of|trailing return type" }
- operator auto*() -> int; // { dg-error "invalid use
of|trailing return type" }
+ operator auto*() -> int; // { dg-error "invalid use
of|trailing return type|cannot be overloaded" }
};
template <typename> struct B
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr80471.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-pr80471.C
index d5fa5a536d3..6ea6164b417 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-pr80471.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr80471.C
@@ -18,6 +18,6 @@ int main()
{
int i;
static_assert(is_same< decltype(f(i)), int& >, "");
- static_assert(is_same< decltype(g(i)), int >, "");
+ static_assert(is_same< decltype(g(i)), int& >, "");
static_assert(is_same< decltype(z(i)), int& >, "");
}
diff --git a/libcc1/libcp1plugin.cc b/libcc1/libcp1plugin.cc
index b466b34bee3..00449f43b52 100644
--- a/libcc1/libcp1plugin.cc
+++ b/libcc1/libcp1plugin.cc
@@ -3343,10 +3343,7 @@ plugin_get_expr_type (cc1_plugin::connection *self,
if (op0)
type = TREE_TYPE (op0);
else
- {
- type = make_decltype_auto ();
- AUTO_IS_DECLTYPE (type) = true;
- }
+ type = make_decltype_auto ();
return convert_out (ctx->preserve (type));
}
--
2.25.0.191.gde93cc14ab
