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

[Jonathan Wakely <jwakely@redhat.com>]

On Thu, 6 Jan 2022 at 10:33, Jonathan Wakely <jwakely@redhat.com> wrote:

>
>
> 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
>

Maybe this one: https://github.com/llvm/llvm-project/issues/38230