Re: [committed] libstdc++: Reduce template instantiations in <regex>

[Jonathan Wakely <jwakely@redhat.com>]

On Thu, 6 Jan 2022 at 10:00, Stephan Bergmann <sbergman@redhat.com> wrote:

> On 05/01/2022 14:47, Jonathan Wakely via Libstdc++ wrote:
> > Tested powerpc64le-linux, pushed to trunk.
> >
> >
> > This moves the last two template parameters of __regex_algo_impl to be
> > runtime function parameters instead, so that we don't need four
> > different instantiations for the possible ways to call it. Most of the
> > function (and what it instantiates) is the same in all cases, so making
> > them compile-time choices doesn't really have much benefit.
> >
> > Use  'if constexpr' for conditions that check template parameters, so
> > that when we do depend on a compile-time condition we only instantiate
> > what we need to.
> >
> > libstdc++-v3/ChangeLog:
> >
> >       * include/bits/regex.h (__regex_algo_impl): Change __policy and
> >       __match_mode template parameters to be function parameters.
> >       (regex_match, regex_search): Pass policy and match mode as
> >       function arguments.
> >       * include/bits/regex.tcc (__regex_algo_impl): Change template
> >       parameters to function parameters.
> >       * include/bits/regex_compiler.h (_RegexTranslatorBase): Use
> >       'if constexpr' for conditions using template parameters.
> >       (_RegexTranslator): Likewise.
> >       * include/bits/regex_executor.tcc (_Executor::_M_handle_accept):
> >       Likewise.
> >       * testsuite/util/testsuite_regex.h (regex_match_debug)
> >       (regex_search_debug): Move template arguments to function
> >       arguments.
> > ---
> >   libstdc++-v3/include/bits/regex.h             | 33 +++++++++----------
> >   libstdc++-v3/include/bits/regex.tcc           |  8 ++---
> >   libstdc++-v3/include/bits/regex_compiler.h    |  9 ++---
> >   libstdc++-v3/include/bits/regex_executor.tcc  |  2 +-
> >   libstdc++-v3/testsuite/util/testsuite_regex.h | 24 +++++++-------
> >   5 files changed, 37 insertions(+), 39 deletions(-)
>
> Clang now fails #include <regex> with
>
> > In file included from
> gcc/trunk/inst/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../include/c++/12.0.0/regex:66:
> >
> gcc/trunk/inst/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/regex.h:799:9:
> error: unknown type name '_RegexExecutorPolicy'; did you mean
> '__detail::_RegexExecutorPolicy'?
> >                                     _RegexExecutorPolicy, bool);
> >                                     ^
> >
> gcc/trunk/inst/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/regex.h:45:14:
> note: '__detail::_RegexExecutorPolicy' declared here
> >   enum class _RegexExecutorPolicy : int { _S_auto, _S_alternate };
> >              ^
> >
> gcc/trunk/inst/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/regex.h:2070:9:
> error: unknown type name '_RegexExecutorPolicy'; did you mean
> '__detail::_RegexExecutorPolicy'?
> >                                     _RegexExecutorPolicy, bool);
> >                                     ^
> >
> gcc/trunk/inst/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/regex.h:45:14:
> note: '__detail::_RegexExecutorPolicy' declared here
> >   enum class _RegexExecutorPolicy : int { _S_auto, _S_alternate };
> >              ^
>
> and
>
> > diff --git a/libstdc++-v3/include/bits/regex.h
> b/libstdc++-v3/include/bits/regex.h
> > index 7480b0a5f97..46c168010bf 100644
> > --- a/libstdc++-v3/include/bits/regex.h
> > +++ b/libstdc++-v3/include/bits/regex.h
> > @@ -796,7 +796,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
> >         __detail::__regex_algo_impl(_Bp, _Bp, match_results<_Bp, _Ap>&,
> >                                     const basic_regex<_Cp, _Rp>&,
> >                                     regex_constants::match_flag_type,
> > -                                   _RegexExecutorPolicy, bool);
> > +                                   __detail::_RegexExecutorPolicy,
> bool);
> >
> >        template<typename, typename, typename, bool>
> >         friend class __detail::_Executor;
> > @@ -2067,7 +2067,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
> >         __detail::__regex_algo_impl(_Bp, _Bp, match_results<_Bp, _Ap>&,
> >                                     const basic_regex<_Cp, _Rp>&,
> >                                     regex_constants::match_flag_type,
> > -                                   _RegexExecutorPolicy, bool);
> > +                                   __detail::_RegexExecutorPolicy,
> bool);
> >
> >        // Reset contents to __size unmatched sub_match objects
> >        // (plus additional objects for prefix, suffix and unmatched sub).
>
> would fix that.
>


I'll make the change, but this looks like a clang bug:
https://godbolt.org/z/bozxYErrc