On Sat, 4 Feb 2023, Jason Merrill wrote:
> On 2/4/23 15:31, Patrick Palka wrote:
> > After r13-5684-g59e0376f607805 the (pruned) callee of a non-dependent
> > CALL_EXPR is a bare FUNCTION_DECL rather than ADDR_EXPR of FUNCTION_DECL.
> > This innocent change revealed that cp_tree_equal doesn't first check
> > dependentness of a CALL_EXPR before treating the callee as a dependent
> > name, which manifests as us incorrectly accepting the first two
> > testcases below and rejecting the third:
> >
> > * In the first testcase, cp_tree_equal incorrectly returns true for
> > the two non-dependent CALL_EXPRs f(0) and f(0) (whose CALL_EXPR_FN
> > are different FUNCTION_DECLs) and so we treat #2 as a redeclaration
> > of #1.
> >
> > * Same issue in the second testcase, for f<int*>() and f<char>().
> >
> > * In the third testcase, cp_tree_equal incorrectly returns true for
> > f<int>() and f<void(*)(int)>() which causes us to conflate the two
> > dependent specializations A<decltype(f<int>()(U()))> and
> > A<decltype(f<void(*)(int)>()(U()))>, leading to a bogus error.
> >
> > This patch fixes this by making called_fns_equal treat two callees as
> > dependent names only if the CALL_EXPRs in question are dependent.
> >
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > trunk/12? Patch generated with -w to ignore noisy whitespace changes.
> >
> > PR c++/107461
> >
> > gcc/cp/ChangeLog:
> >
> > * pt.cc (iterative_hash_template_arg) <case CALL_EXPR>: Treat
> > the callee as a dependent name only if the CALL_EXPR is
> > dependent.
> > * tree.cc (called_fns_equal): Take two CALL_EXPRs instead of
> > CALL_EXPR_FNs thereof. As above.
> > (cp_tree_equal) <case CALL_EXPR>: Adjust call to called_fns_equal.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/cpp0x/overload5.C: New test.
> > * g++.dg/cpp0x/overload5a.C: New test.
> > * g++.dg/cpp0x/overload6.C: New test.
> > ---
> > gcc/cp/pt.cc | 1 +
> > gcc/cp/tree.cc | 33 ++++++++++++++-----------
> > gcc/testsuite/g++.dg/cpp0x/overload5.C | 12 +++++++++
> > gcc/testsuite/g++.dg/cpp0x/overload5a.C | 10 ++++++++
> > gcc/testsuite/g++.dg/cpp0x/overload6.C | 16 ++++++++++++
> > 5 files changed, 58 insertions(+), 14 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/cpp0x/overload5.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp0x/overload5a.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp0x/overload6.C
> >
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index 255332dc0c1..c9360240cd2 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -1841,6 +1841,7 @@ iterative_hash_template_arg (tree arg, hashval_t val)
> > case CALL_EXPR:
> > {
> > tree fn = CALL_EXPR_FN (arg);
> > + if (TREE_TYPE (arg) == NULL_TREE)
>
> How about changing dependent_name to take the CALL_EXPR rather than the
> CALL_EXPR_FN? That would mean some changes to write_expression to move the
> dependent_name handling into the CALL_EXPR handling, but that doesn't seem
> like a bad thing. Other callers seem like a trivial change.
Indeed changing dependent_name seems best, but I'm worried about such a
refactoring to write_expression causing unintended mangling changes at
this stage. Because it seems the CALL_EXPR case of write_expression
isn't the user of the dependent_name branch of write_expression, at
least according to the following patch which causes us to ICE on
mangle{37,57,58,76}.C:
diff --git a/gcc/cp/mangle.cc b/gcc/cp/mangle.cc
index f2cda3be2cf..700857f8f3c 100644
--- a/gcc/cp/mangle.cc
+++ b/gcc/cp/mangle.cc
@@ -3450,6 +3450,7 @@ write_expression (tree expr)
}
else if (dependent_name (expr))
{
+ gcc_unreachable ();
tree name = dependent_name (expr);
if (IDENTIFIER_ANY_OP_P (name))
{
@@ -3554,7 +3555,19 @@ write_expression (tree expr)
&& type_dependent_expression_p_push (expr))
fn = OVL_NAME (fn);
- write_expression (fn);
+ if (tree name = dependent_name (fn))
+ {
+ if (IDENTIFIER_ANY_OP_P (name))
+ {
+ if (abi_version_at_least (16))
+ write_string ("on");
+ if (abi_warn_or_compat_version_crosses (16))
+ G.need_abi_warning = 1;
+ }
+ write_unqualified_id (name);
+ }
+ else
+ write_expression (fn);
}
for (i = 0; i < call_expr_nargs (expr); ++i)
And since the CALL_EXPR case of write_expression looks through an
ADDR_EXPR callee before recursing, IIUC the refactoring would need to
make dependent_name look through an ADDR_EXPR callee as well, which
seems like a desirable/correct change but I'm worried that might have
unintended consequences as well.
>
> > if (tree name = dependent_name (fn))
> > {
> > if (TREE_CODE (fn) == TEMPLATE_ID_EXPR)
> > diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
> > index c1da868732b..3a57e71b76e 100644
> > --- a/gcc/cp/tree.cc
> > +++ b/gcc/cp/tree.cc
> > @@ -3870,16 +3870,21 @@ decl_internal_context_p (const_tree decl)
> > return !TREE_PUBLIC (decl);
> > }
> > -/* Subroutine of cp_tree_equal: t1 and t2 are the CALL_EXPR_FNs of two
> > - CALL_EXPRS. Return whether they are equivalent. */
> > +/* Subroutine of cp_tree_equal: t1 and t2 are two CALL_EXPRs.
> > + Return whether their CALL_EXPR_FNs are equivalent. */
> > static bool
> > called_fns_equal (tree t1, tree t2)
> > +{
> > + tree fn1 = CALL_EXPR_FN (t1);
> > + tree fn2 = CALL_EXPR_FN (t2);
> > + if (TREE_TYPE (t1) == NULL_TREE
> > + && TREE_TYPE (t2) == NULL_TREE)
> > {
> > /* Core 1321: dependent names are equivalent even if the overload
> > sets
> > are different. But do compare explicit template arguments. */
> > - tree name1 = dependent_name (t1);
> > - tree name2 = dependent_name (t2);
> > + tree name1 = dependent_name (fn1);
> > + tree name2 = dependent_name (fn2);
> > if (name1 || name2)
> > {
> > tree targs1 = NULL_TREE, targs2 = NULL_TREE;
> > @@ -3891,19 +3896,19 @@ called_fns_equal (tree t1, tree t2)
> > of whether the function was named with a qualified- or
> > unqualified-id.
> > Until that's fixed, check that we aren't looking at overload sets
> > from
> > different scopes. */
> > - if (is_overloaded_fn (t1) && is_overloaded_fn (t2)
> > - && (DECL_CONTEXT (get_first_fn (t1))
> > - != DECL_CONTEXT (get_first_fn (t2))))
> > + if (is_overloaded_fn (fn1) && is_overloaded_fn (fn2)
> > + && (DECL_CONTEXT (get_first_fn (fn1))
> > + != DECL_CONTEXT (get_first_fn (fn2))))
> > return false;
> > - if (TREE_CODE (t1) == TEMPLATE_ID_EXPR)
> > - targs1 = TREE_OPERAND (t1, 1);
> > - if (TREE_CODE (t2) == TEMPLATE_ID_EXPR)
> > - targs2 = TREE_OPERAND (t2, 1);
> > + if (TREE_CODE (fn1) == TEMPLATE_ID_EXPR)
> > + targs1 = TREE_OPERAND (fn1, 1);
> > + if (TREE_CODE (fn2) == TEMPLATE_ID_EXPR)
> > + targs2 = TREE_OPERAND (fn2, 1);
> > return cp_tree_equal (targs1, targs2);
> > }
> > - else
> > - return cp_tree_equal (t1, t2);
> > + }
> > + return cp_tree_equal (fn1, fn2);
> > }
> > bool comparing_override_contracts;
> > @@ -4037,7 +4042,7 @@ cp_tree_equal (tree t1, tree t2)
> > if (KOENIG_LOOKUP_P (t1) != KOENIG_LOOKUP_P (t2))
> > return false;
> > - if (!called_fns_equal (CALL_EXPR_FN (t1), CALL_EXPR_FN (t2)))
> > + if (!called_fns_equal (t1, t2))
> > return false;
> > call_expr_arg_iterator iter1, iter2;
> > diff --git a/gcc/testsuite/g++.dg/cpp0x/overload5.C
> > b/gcc/testsuite/g++.dg/cpp0x/overload5.C
> > new file mode 100644
> > index 00000000000..e05b1594f51
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp0x/overload5.C
> > @@ -0,0 +1,12 @@
> > +// PR c++/107461
> > +// { dg-do compile { target c++11 } }
> > +
> > +int f(...);
> > +template<class T> decltype(T() + f(0)) g(); // #1
> > +
> > +char f(int);
> > +template<class T> decltype(T() + f(0)) g(); // #2, distinct from #1
> > +
> > +int main() {
> > + g<int>(); // { dg-error "ambiguous" }
> > +}
> > diff --git a/gcc/testsuite/g++.dg/cpp0x/overload5a.C
> > b/gcc/testsuite/g++.dg/cpp0x/overload5a.C
> > new file mode 100644
> > index 00000000000..037114f199c
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp0x/overload5a.C
> > @@ -0,0 +1,10 @@
> > +// PR c++/107461
> > +// { dg-do compile { target c++11 } }
> > +
> > +template<class T> T f();
> > +template<class T> decltype(T() + f<int*>()) g(); // #1
> > +template<class T> decltype(T() + f<char>()) g(); // #2, distinct from #1
> > +
> > +int main() {
> > + g<int>(); // { dg-error "ambiguous" }
> > +}
> > diff --git a/gcc/testsuite/g++.dg/cpp0x/overload6.C
> > b/gcc/testsuite/g++.dg/cpp0x/overload6.C
> > new file mode 100644
> > index 00000000000..1fbee0501de
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp0x/overload6.C
> > @@ -0,0 +1,16 @@
> > +// PR c++/107461
> > +// { dg-do compile { target c++11 } }
> > +
> > +template<class T> T f();
> > +
> > +template<class> struct A { };
> > +
> > +template<class T> struct B {
> > + template<class U, class = A<decltype(f<T>()(U()))>>
> > + static void g(U);
> > +};
> > +
> > +int main() {
> > + B<int> b;
> > + B<void(*)(int)>::g(0); // { dg-bogus "no match" }
> > +}
>
>
