| Message ID | 20240307120630.482384-1-jwakely@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | libstdc++: Document that _GLIBCXX_CONCEPT_CHECKS might be removed in future | expand |
On Thu, 7 Mar 2024 at 12:07, Jonathan Wakely wrote: > > Any objection to this update to make the docs reflect reality? Pushed to trunk now. > > -- >8 -- > > The macro-based concept checks are unmaintained and do not support C++11 > or later, so reject valid code. If nobody plans to update them we should > consider removing them. Alternatively, we could ignore the macro for > C++11 and later, so they have no effect and don't reject valid code. > > libstdc++-v3/ChangeLog: > > * doc/xml/manual/debug.xml: Document that concept checking might > be removed in future. > * doc/xml/manual/extensions.xml: Likewise. > --- > libstdc++-v3/doc/xml/manual/debug.xml | 2 ++ > libstdc++-v3/doc/xml/manual/extensions.xml | 18 ++++++++++++------ > 2 files changed, 14 insertions(+), 6 deletions(-) > > diff --git a/libstdc++-v3/doc/xml/manual/debug.xml b/libstdc++-v3/doc/xml/manual/debug.xml > index 42d4d32aa29..7f6d0876fc6 100644 > --- a/libstdc++-v3/doc/xml/manual/debug.xml > +++ b/libstdc++-v3/doc/xml/manual/debug.xml > @@ -351,6 +351,8 @@ > > <para> The <link linkend="manual.ext.compile_checks">Compile-Time > Checks</link> extension has compile-time checks for many algorithms. > + These checks were designed for C++98 and have not been updated to work > + with C++11 and later standards. They might be removed at a future date. > </para> > </section> > > diff --git a/libstdc++-v3/doc/xml/manual/extensions.xml b/libstdc++-v3/doc/xml/manual/extensions.xml > index d4fe2f509d4..490a50cc331 100644 > --- a/libstdc++-v3/doc/xml/manual/extensions.xml > +++ b/libstdc++-v3/doc/xml/manual/extensions.xml > @@ -77,8 +77,7 @@ extensions, be aware of two things: > object file. The checks are also cleaner and easier to read and > understand. > </para> > - <para>They are off by default for all versions of GCC from 3.0 to 3.4 (the > - latest release at the time of writing). > + <para>They are off by default for all GCC 3.0 and all later versions. > They can be enabled at configure time with > <link linkend="manual.intro.setup.configure"><literal>--enable-concept-checks</literal></link>. > You can enable them on a per-translation-unit basis with > @@ -89,10 +88,17 @@ extensions, be aware of two things: > </para> > > <para>Please note that the concept checks only validate the requirements > - of the old C++03 standard. C++11 was expected to have first-class > - support for template parameter constraints based on concepts in the core > - language. This would have obviated the need for the library-simulated concept > - checking described above, but was not part of C++11. > + of the old C++03 standard and reject some valid code that meets the relaxed > + requirements of C++11 and later standards. > + C++11 was expected to have first-class support for template parameter > + constraints based on concepts in the core language. > + This would have obviated the need for the library-simulated concept checking > + described above, but was not part of C++11. > + C++20 adds a different model of concepts, which is now used to constrain > + some new parts of the C++20 library, e.g. the > + <filename><ranges></filename> header and the new overloads in the > + <filename><algorithm></filename> header for working with ranges. > + The old library-simulated concept checks might be removed at a future date. > </para> > > </chapter> > -- > 2.43.2 >
diff --git a/libstdc++-v3/doc/xml/manual/debug.xml b/libstdc++-v3/doc/xml/manual/debug.xml index 42d4d32aa29..7f6d0876fc6 100644 --- a/libstdc++-v3/doc/xml/manual/debug.xml +++ b/libstdc++-v3/doc/xml/manual/debug.xml @@ -351,6 +351,8 @@ <para> The <link linkend="manual.ext.compile_checks">Compile-Time Checks</link> extension has compile-time checks for many algorithms. + These checks were designed for C++98 and have not been updated to work + with C++11 and later standards. They might be removed at a future date. </para> </section> diff --git a/libstdc++-v3/doc/xml/manual/extensions.xml b/libstdc++-v3/doc/xml/manual/extensions.xml index d4fe2f509d4..490a50cc331 100644 --- a/libstdc++-v3/doc/xml/manual/extensions.xml +++ b/libstdc++-v3/doc/xml/manual/extensions.xml @@ -77,8 +77,7 @@ extensions, be aware of two things: object file. The checks are also cleaner and easier to read and understand. </para> - <para>They are off by default for all versions of GCC from 3.0 to 3.4 (the - latest release at the time of writing). + <para>They are off by default for all GCC 3.0 and all later versions. They can be enabled at configure time with <link linkend="manual.intro.setup.configure"><literal>--enable-concept-checks</literal></link>. You can enable them on a per-translation-unit basis with @@ -89,10 +88,17 @@ extensions, be aware of two things: </para> <para>Please note that the concept checks only validate the requirements - of the old C++03 standard. C++11 was expected to have first-class - support for template parameter constraints based on concepts in the core - language. This would have obviated the need for the library-simulated concept - checking described above, but was not part of C++11. + of the old C++03 standard and reject some valid code that meets the relaxed + requirements of C++11 and later standards. + C++11 was expected to have first-class support for template parameter + constraints based on concepts in the core language. + This would have obviated the need for the library-simulated concept checking + described above, but was not part of C++11. + C++20 adds a different model of concepts, which is now used to constrain + some new parts of the C++20 library, e.g. the + <filename><ranges></filename> header and the new overloads in the + <filename><algorithm></filename> header for working with ranges. + The old library-simulated concept checks might be removed at a future date. </para> </chapter>