On Fri, 20 Oct 2023, Jason Merrill wrote: > Tested x86_64-pc-linux-gnu, applying to trunk. Patrick, sorry I didn't apply > this sooner. > > -- 8< -- > > In r13-3766 I changed the logic at the end of tourney to avoid redundant > comparisons, but the change also meant skipping any less-good matches > between the champ_compared_to_predecessor candidate and champ itself. > > This should not be a correctness issue, since we believe that joust is a > partial order. But it can lead to missed warnings, as in this testcase.
I suppose this rules out optimizing tourney via transitivity when in a non-SFINAE context since it'd cause missed warnings such as these. But maybe we'd still want to optimize the second pass via transitivity in a SFINAE context? > > gcc/cp/ChangeLog: > > * call.cc (tourney): Only skip champ_compared_to_predecessor. > > gcc/testsuite/ChangeLog: > > * g++.dg/warn/Wsign-promo1.C: New test. > --- > gcc/cp/call.cc | 5 +++-- > gcc/testsuite/g++.dg/warn/Wsign-promo1.C | 15 +++++++++++++++ > 2 files changed, 18 insertions(+), 2 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/warn/Wsign-promo1.C > > diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc > index 657eca93d23..a49fde949d5 100644 > --- a/gcc/cp/call.cc > +++ b/gcc/cp/call.cc > @@ -13227,10 +13227,11 @@ tourney (struct z_candidate *candidates, > tsubst_flags_t complain) > been compared to. */ > > for (challenger = candidates; > - challenger != champ > - && challenger != champ_compared_to_predecessor; > + challenger != champ; > challenger = challenger->next) > { > + if (challenger == champ_compared_to_predecessor) > + continue; > fate = joust (champ, challenger, 0, complain); > if (fate != 1) > return NULL; > diff --git a/gcc/testsuite/g++.dg/warn/Wsign-promo1.C > b/gcc/testsuite/g++.dg/warn/Wsign-promo1.C > new file mode 100644 > index 00000000000..51b76eee735 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/warn/Wsign-promo1.C > @@ -0,0 +1,15 @@ > +// Check that we get joust warnings from comparing the final champ to a > +// candidate between it and the previous champ. > + > +// { dg-additional-options -Wsign-promo } > + > +struct A { A(int); }; > + > +enum E { e }; > + > +int f(int, A); > +int f(unsigned, A); > +int f(int, int); > + > +int i = f(e, 42); // { dg-warning "passing 'E'" } > +// { dg-warning "in call to 'int f" "" { target *-*-* } .-1 } > > base-commit: 084addf8a700fab9222d4127ab8524920d0ca481 > -- > 2.39.3 > >