On Fri, 22 Jan 2021, Jason Merrill wrote:
On 1/22/21 1:58 PM, Patrick Palka wrote:
On Fri, 22 Jan 2021, Jason Merrill wrote:
On 1/22/21 12:59 PM, Patrick Palka wrote:
On Fri, 22 Jan 2021, Patrick Palka wrote:
On Fri, 22 Jan 2021, Patrick Palka wrote:
On Thu, 21 Jan 2021, Jason Merrill wrote:
On 1/21/21 11:22 AM, Patrick Palka wrote:
Here at parse time finish_qualified_id_expr adds an implicit
'this->' to
the expression tmp::integral<T> (because it's type-dependent,
and
also
current_class_ptr is set) within the trailing return type, and
later
during substitution we can't resolve the 'this' since
tsubst_function_type does inject_this_parm only for non-static
member
functions which tmp::func is not.
It seems the root of the problem is that we set
current_class_ptr
when
parsing the signature of a static member function. Since
explicit
uses
of 'this' are already not allowed in this context, we probably
shouldn't
be doing inject_this_parm either.
Hmm, 'this' is defined in a static member function, it's just
ill-formed to
use it:
7.5.2/2: "... [this] shall not appear within the declaration of a
static
member function (although its type and value category are defined
within a
static member function as they are within a non-static member
function).
[Note: This is because declaration matching does not occur until
the
complete
declarator is known. — end note]"
Ah, I see.
Perhaps maybe_dummy_object needs to be smarter about recognizing
static
context. Or perhaps there's no way to tell the difference between
the
specified behavior above and the behavior with your patch, but:
The note suggests that we need to test the case of an out-of-class
definition
of a static member function (template); we must inject_this_parm
when
parsing
such a declaration, since we don't know it's static until we match
it
to the
declaration in the class. I'm guessing that this would lead to
the
same
problem.
Good point, we do get a signature mismatch error in this case, due
to
'this->' appearing in the trailing return type out-of-class
declaration
but not in that of the in-class declaration, so the trailing return
types don't match up. In light of this case, it doesn't seem
possible
for maybe_dummy_object to distinguish between a static and
non-static
context when parsing the trailing return type of the declaration.
So perhaps we should mirror at substitution time what we do at parse
time, and inject 'this' also when substituting into the function
type of
a static member function? That way, we'll resolve the use of
'this->'
and then discard it the RHS of -> is a static member function, or
complain that 'this' is not a constant expression if the RHS is a
non-static member function.
The following patch performs that, and seems to pass light testing.
Full testing in progress. Revised commit message is still a WIP.
How does this approach look?
Sorry for the spam, but I'd also like to propose a more conservative and
targeted approach that basically undoes part of the r9-5972 patch which
caused the regression.
According to the email thread at
https://gcc.gnu.org/pipermail/gcc-patches/2019-February/516421.html
the hunk from r9-5972
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -2096,7 +2096,8 @@ finish_qualified_id_expr (tree qualifying_class,
{
/* See if any of the functions are non-static members. */
/* If so, the expression may be relative to 'this'. */
- if (!shared_member_p (expr)
+ if ((type_dependent_expression_p (expr)
+ || !shared_member_p (expr))
&& current_class_ptr
&& DERIVED_FROM_P (qualifying_class,
current_nonlambda_class_type ()))
was added to avoid calling shared_member_p here when the overload set
contains a dependent USING_DECL. But according to
https://gcc.gnu.org/pipermail/gcc-patches/2018-December/513237.html if
an overload set contains a dependent USING_DECL, then it'll be the first
in the overload set. So we could partially revert the r9-5972 patch and
do:
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index c6b4c70dc0f..6b0d68ae4bf 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -2214,7 +2214,7 @@ finish_qualified_id_expr (tree qualifying_class,
{
/* See if any of the functions are non-static members. */
/* If so, the expression may be relative to 'this'. */
- if ((type_dependent_expression_p (expr)
+ if ((TREE_CODE (get_first_fn (expr)) == USING_DECL
|| !shared_member_p (expr))
&& current_class_ptr
&& DERIVED_FROM_P (qualifying_class,
The above pases 'make check-c++', and allows us to compile pr97399a.C
successfully, but we'd still ICE on the invalid pr97399b.C.
What if we flipped the sense of the type_dependent_expression_p check, so
we
never add this-> if the function operand is dependent?
Looks like this doesn't survive 'make check-c++', we crash on the
testcase g++.dg/cpp1y/lambda-generic-this1a.C:
gcc/testsuite/g++.dg/cpp1y/lambda-generic-this1a.C: In instantiation of
‘MyType::crash()::<lambda(auto:1)> [with auto:1 = A]’:
gcc/testsuite/g++.dg/cpp1y/lambda-generic-this1a.C:12:10: required from
here
gcc/testsuite/g++.dg/cpp1y/lambda-generic-this1a.C:9:28: internal compiler
error: trying to capture ‘this’ in instantiation of generic lambda
9 | MyType::make_crash<i>(); // Line (1)
| ~~~~~~~~~~~~~~~~~~~~~^~
0x9bab23 add_capture(tree_node*, tree_node*, tree_node*, bool, bool)
/home/patrick/gcc-master/gcc/cp/lambda.c:633
0x9bac75 add_default_capture(tree_node*, tree_node*, tree_node*)
/home/patrick/gcc-master/gcc/cp/lambda.c:693
0x9bb3a1 lambda_expr_this_capture(tree_node*, int)
/home/patrick/gcc-master/gcc/cp/lambda.c:811
0x9bb4a0 maybe_resolve_dummy(tree_node*, bool)
/home/patrick/gcc-master/gcc/cp/lambda.c:894
0x8de510 build_new_method_call_1
/home/patrick/gcc-master/gcc/cp/call.c:10503
0x8df04f build_new_method_call(tree_node*, tree_node*, vec<tree_node*,
va_gc, vl_embed>**, tree_node*, int, tree_node**, int)
Presumably because we no longer add 'this->' to the dependent call
MyType::make_crash<i> inside the generic lambda, so we don't capture it
when we should have?
Ah, yes, we still need to add this-> in a generic lambda, or at least capture
'this'.
I think I was wrong in my assertion around Alex's patch that shared_member_p
should abort on a dependent USING_DECL; it now seems appropriate for it to
return false if we don't know, we just need to adjust the comment to say that.
And then drop the type-dependent check.
Sounds good, thanks a lot. Here's what I'm testing.
Note that with this approach we still ICE on the invalid testcase
pr97399b.C (starting with r8-2724, it seems). I'll create a separate PR
to track this issue.
-- >8 --
Subject: [PATCH] c++: 'this' injection and static member functions [PR97399]
In the testcase pr97399.C below, finish_qualified_id_expr at parse time
adds an implicit 'this->' to the expression tmp::integral<T> (because
it's type-dependent, and also current_class_ptr is set at this point)
within the trailing return type. Later when substituting into the
trailing return type we crash due to the unresolved 'this', since
tsubst_function_type does inject_this_parm only for non-static member
functions, which tmp::func is not.
This patch fixes this issue by removing the type-dependence check
in finish_qualified_id_expr added by r9-5972, and in its place relaxing
shared_member_p to handle dependent USING_DECLs:
I think I was wrong in my assertion around Alex's patch that
shared_member_p should abort on a dependent USING_DECL; it now seems
appropriate for it to return false if we don't know, we just need to
adjust the comment to say that.
Moreover, for friend functions, we shouldn't be setting
current_class_ptr at all when parsing its signature, so this patch
suppresses inject_this_parm for friends.
Finally, the change to cp_parser_init_declarator below is needed so that
we properly communicate static-ness to cp_parser_direct_declarator when
parsing a member function template. This lets us reject the explicit
use of 'this' in the testcase this2.C below.
Bootstrap and regtest re-running on x86_64-pc-linux-gnu, does this look
OK for trunk if successful?
gcc/cp/ChangeLog:
PR c++/97399
* cp-tree.h (shared_member_p): Adjust declaration.
* parser.c (cp_parser_init_declarator): If the storage class
specifier is sc_static, pass true for static_p to
cp_parser_declarator.
(cp_parser_direct_declarator): Don't do inject_this_parm when
the function is specified as a friend.
* search.c (shared_member_p): Change return type to bool and
adjust return statements accordingly. Return false for a
dependent USING_DECL.
* pt.c (tsubst_function_type): Also inject 'this' when
substituting into the function type of a static member
function.
gcc/testsuite/ChangeLog:
PR c++/88548
PR c++/97399
* g++.dg/cpp0x/this2.C: New test.
* g++.dg/template/pr97399.C: New test.
---
gcc/cp/cp-tree.h | 2 +-
gcc/cp/parser.c | 5 +++--
gcc/cp/search.c | 20 +++++++++++---------
gcc/cp/semantics.c | 3 +--
gcc/testsuite/g++.dg/cpp0x/this2.C | 8 ++++++++
gcc/testsuite/g++.dg/template/pr97399.C | 23 +++++++++++++++++++++++
6 files changed, 47 insertions(+), 14 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/this2.C
create mode 100644 gcc/testsuite/g++.dg/template/pr97399.C
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index eb20de433b7..65b4cc7f5c8 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7312,7 +7312,7 @@ extern tree adjust_result_of_qualified_name_lookup
(tree, tree, tree);
extern tree copied_binfo (tree, tree);
extern tree original_binfo (tree, tree);
-extern int shared_member_p (tree);
+extern bool shared_member_p (tree);
extern bool any_dependent_bases_p (tree = current_nonlambda_class_type ());
extern bool maybe_check_overriding_exception_spec (tree, tree);
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 48437f23175..3a78ea49634 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -21413,6 +21413,7 @@ cp_parser_init_declarator (cp_parser* parser,
bool is_non_constant_init;
int ctor_dtor_or_conv_p;
bool friend_p = cp_parser_friend_p (decl_specifiers);
+ bool static_p = decl_specifiers->storage_class == sc_static;
tree pushed_scope = NULL_TREE;
bool range_for_decl_p = false;
bool saved_default_arg_ok_p = parser->default_arg_ok_p;
@@ -21446,7 +21447,7 @@ cp_parser_init_declarator (cp_parser* parser,
= cp_parser_declarator (parser, CP_PARSER_DECLARATOR_NAMED,
flags, &ctor_dtor_or_conv_p,
/*parenthesized_p=*/NULL,
- member_p, friend_p, /*static_p=*/false);
+ member_p, friend_p, static_p);
/* Gather up the deferred checks. */
stop_deferring_access_checks ();
@@ -22122,7 +22123,7 @@ cp_parser_direct_declarator (cp_parser* parser,
tree save_ccp = current_class_ptr;
tree save_ccr = current_class_ref;
- if (memfn)
+ if (memfn && !friend_p)
/* DR 1207: 'this' is in scope after the cv-quals. */
inject_this_parameter (current_class_type, cv_quals);
diff --git a/gcc/cp/search.c b/gcc/cp/search.c
index dd3773da4f7..9c60c80da44 100644
--- a/gcc/cp/search.c
+++ b/gcc/cp/search.c
@@ -910,7 +910,7 @@ struct lookup_field_info {
const char *errstr;
};
-/* Nonzero for a class member means that it is shared between all objects
+/* True for a class member means that it is shared between all objects
of that class.
[class.member.lookup]:If the resulting set of declarations are not all
@@ -920,25 +920,27 @@ struct lookup_field_info {
This function checks that T contains no non-static members. */
-int
+bool
shared_member_p (tree t)
{
- if (VAR_P (t) || TREE_CODE (t) == TYPE_DECL \
+ if (VAR_P (t) || TREE_CODE (t) == TYPE_DECL
|| TREE_CODE (t) == CONST_DECL)
- return 1;
+ return true;
if (is_overloaded_fn (t))
{
for (ovl_iterator iter (get_fns (t)); iter; ++iter)
{
tree decl = strip_using_decl (*iter);
- /* We don't expect or support dependent decls. */
- gcc_assert (TREE_CODE (decl) != USING_DECL);
+ if (TREE_CODE (decl) == USING_DECL)
+ /* We don't know what this dependent using declaration
+ will resolve to; conservatively return false. */
+ return false;
if (DECL_NONSTATIC_MEMBER_FUNCTION_P (decl))
- return 0;
+ return false;
}
- return 1;
+ return true;
}
- return 0;
+ return false;
}
/* Routine to see if the sub-object denoted by the binfo PARENT can be
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 067095276af..51841dcf24a 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -2214,8 +2214,7 @@ finish_qualified_id_expr (tree qualifying_class,
{
/* See if any of the functions are non-static members. */
/* If so, the expression may be relative to 'this'. */
- if ((type_dependent_expression_p (expr)
- || !shared_member_p (expr))
+ if (!shared_member_p (expr)
&& current_class_ptr
&& DERIVED_FROM_P (qualifying_class,
current_nonlambda_class_type ()))
diff --git a/gcc/testsuite/g++.dg/cpp0x/this2.C
b/gcc/testsuite/g++.dg/cpp0x/this2.C
new file mode 100644
index 00000000000..3781bc5efec
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/this2.C
@@ -0,0 +1,8 @@
+// PR c++/88548
+// { dg-do compile { target c++11 } }
+
+struct S {
+ int a;
+ template <class> static auto m1 ()
+ -> decltype(this->a) { return 0; }; // { dg-error "'this'" }
+};
diff --git a/gcc/testsuite/g++.dg/template/pr97399.C
b/gcc/testsuite/g++.dg/template/pr97399.C
new file mode 100644
index 00000000000..4bb818908fd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/pr97399.C
@@ -0,0 +1,23 @@
+// PR c++/97399
+// { dg-do compile { target c++11 } }
+
+template <bool> struct enable_if_t {};
+
+struct tmp {
+ template <class> static constexpr bool is_integral();
+ template <class T> static auto f()
+ -> enable_if_t<tmp::is_integral<T>()>;
+ template <class T> friend auto g(tmp, T)
+ -> enable_if_t<!tmp::is_integral<T>()>;
+};
+
+template <class> constexpr bool tmp::is_integral() { return true; }
+
+template <class T> auto tmp::f()
+ -> enable_if_t<tmp::is_integral<T>()> { return {}; }
+
+int main()
+{
+ tmp::f<int>();
+ g(tmp{}, 0);
+}
