On Sun, 17 Sep 2023, Jason Merrill wrote:
> On 9/17/23 15:13, Patrick Palka wrote:
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > trunk?
> >
> > -- >8 --
> >
> > r14-2655-g92d1425ca78040 made instantiate_template avoid redundantly
> > performing a specialization lookup when instantiating a function or
> > alias template. This patch applies the same optimization to
> > tsubst_template_decl when (partially) instantiating a function template,
> > which allows us to remove a check from register_specialization since
> > tsubst_function_decl no longer calls register_specialization for
> > a function template partial instantiation.
> >
> > gcc/cp/ChangeLog:
> >
> > * pt.cc (register_specialization): Remove now-unnecessary
> > early exit for FUNCTION_DECL partial instantiation.
> > (tsubst_template_decl): Pass use_spec_table=false to
> > tsubst_function_decl. Set DECL_TI_ARGS of a non-lambda
> > FUNCTION_DECL specialization to the full set of arguments.
> > Simplify register_specialization call accordingly.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/template/nontype12.C: Expect two instead of three
> > duplicate diagnostics for A<double>::bar() specialization.
> > ---
> > gcc/cp/pt.cc | 29 +++++++----------------
> > gcc/testsuite/g++.dg/template/nontype12.C | 1 -
> > 2 files changed, 9 insertions(+), 21 deletions(-)
> >
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index c311a6b88f5..a0296a1ea16 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -1507,21 +1507,6 @@ register_specialization (tree spec, tree tmpl, tree
> > args, bool is_friend,
> > || (TREE_CODE (tmpl) == FIELD_DECL
> > && TREE_CODE (spec) == NONTYPE_ARGUMENT_PACK));
> > - if (TREE_CODE (spec) == FUNCTION_DECL
> > - && uses_template_parms (DECL_TI_ARGS (spec)))
> > - /* This is the FUNCTION_DECL for a partial instantiation. Don't
> > - register it; we want the corresponding TEMPLATE_DECL instead.
> > - We use `uses_template_parms (DECL_TI_ARGS (spec))' rather than
> > - the more obvious `uses_template_parms (spec)' to avoid problems
> > - with default function arguments. In particular, given
> > - something like this:
> > -
> > - template <class T> void f(T t1, T t = T())
> > -
> > - the default argument expression is not substituted for in an
> > - instantiation unless and until it is actually needed. */
> > - return spec;
> > -
> > spec_entry elt;
> > elt.tmpl = tmpl;
> > elt.args = args;
> > @@ -14663,7 +14648,7 @@ tsubst_template_decl (tree t, tree args,
> > tsubst_flags_t complain,
> > tree in_decl = t;
> > tree spec;
> > tree tmpl_args;
> > - tree full_args;
> > + tree full_args = NULL_TREE;
> > tree r;
> > hashval_t hash = 0;
> > @@ -14754,7 +14739,8 @@ tsubst_template_decl (tree t, tree args,
> > tsubst_flags_t complain,
> > tree inner = decl;
> > ++processing_template_decl;
> > if (TREE_CODE (inner) == FUNCTION_DECL)
> > - inner = tsubst_function_decl (inner, args, complain, lambda_fntype);
> > + inner = tsubst_function_decl (inner, args, complain, lambda_fntype,
> > + /*use_spec_table=*/false);
> > else
> > {
> > if (TREE_CODE (inner) == TYPE_DECL && !TYPE_DECL_ALIAS_P (inner))
> > @@ -14792,6 +14778,11 @@ tsubst_template_decl (tree t, tree args,
> > tsubst_flags_t complain,
> > }
> > else
> > {
> > + if (TREE_CODE (inner) == FUNCTION_DECL)
> > + /* Set DECL_TI_ARGS to the full set of template arguments, which
> > + tsubst_function_decl didn't do due to use_spec_table=false. */
> > + DECL_TI_ARGS (inner) = full_args;
> > +
> > DECL_TI_TEMPLATE (inner) = r;
> > DECL_TI_ARGS (r) = DECL_TI_ARGS (inner);
> > }
> > @@ -14822,9 +14813,7 @@ tsubst_template_decl (tree t, tree args,
> > tsubst_flags_t complain,
> > if (TREE_CODE (decl) == FUNCTION_DECL && !lambda_fntype)
> > /* Record this non-type partial instantiation. */
> > - register_specialization (r, t,
> > - DECL_TI_ARGS (DECL_TEMPLATE_RESULT (r)),
> > - false, hash);
> > + register_specialization (r, t, full_args, false, hash);
> > return r;
> > }
> > diff --git a/gcc/testsuite/g++.dg/template/nontype12.C
> > b/gcc/testsuite/g++.dg/template/nontype12.C
> > index 9a9c3ac1e66..e36a9f16f94 100644
> > --- a/gcc/testsuite/g++.dg/template/nontype12.C
> > +++ b/gcc/testsuite/g++.dg/template/nontype12.C
> > @@ -5,7 +5,6 @@ template<typename T> struct A
> > {
> > template<T> int foo(); // { dg-error "double" ""
> > { target c++17_down } }
> > template<template<T> class> int bar(); // { dg-bogus
> > {double[^\n]*\n[^\n]*C:7:[^\n]*double} "" { xfail c++17_down } }
> > - // { dg-error "double" "" { target c++17_down } .-1 }
>
> Hmm, I thought this line was to check that we get one error even if we don't
> want two?
The xfailed dg-bogus directive seems to "consume" the two errors, and
prevents the dg-error from matching either of them. Before this patch,
we issued three duplicate errors and so this arrangement worked out
since the xfailed dg-bogus consumes only two of the errors. I'm not
sure how to express that we're currently seeing two errors but only want
one using _both_ dg-error and dg-bogus..
>
> Jason
>
