On Tue, Jan 19, 2021 at 11:28 PM Jason Merrill <ja...@redhat.com> wrote:
>
> On 1/10/21 7:28 PM, Paul Fee via Gcc-patches wrote:
> > [PATCH v2] c++: Add support for -std=c++2b
>
> Thanks!
>
> This patch was corrupted by word wrap, so it won't apply; if you can't
> suppress word wrap in your mail client, please send the patch as an
> attachment instead.
Seems that "Plain text mode" in gmail isn't plain enough. I'll use an
attachment for patch v3.
>
> Also remember to use git gcc-verify before sending the patch.
Thanks for the tip. It helps me learn the GCC patch posting process.
>
> > Derived from the changes that added C++2a support in 2017.
> > https://gcc.gnu.org/g:026a79f70cf33f836ea5275eda72d4870a3041e5
> >
> > No C++2b features are added here.
> > Use of -std=c++2b sets __cplusplus to 202100L.
> >
> > $ g++ -std=c++2b -dM -E -x c++ - < /dev/null | grep cplusplus
> > #define __cplusplus 202100L
> >
> > Changes since v1 (8th Jan 2021):
> > * As suggested by Jonathan Wakely:
> > __cplusplus set to 202100L rather than 202101L. Use of a non-existent
> > date
> > helps indicate this is not a true standard, yet is a value greater
> > than 202002L.
> > * As suggested by Jakub Jelinek:
> > Fixed typos and formatting.
> > Added C++23 support to dwarf2out.c, including missing C++20 support
> > in highest_c_language.
>
> > * Regarding suggestion by Marek Polacek to refer to C++23 rather than C++2b.
> > Left the option as -std=c++2b for now. It may be premature to assume
> > the next
> > version of the standard will be named C++23. Use of c++2b also
> > reinforces
> > the experimental nature of GCC's C++23 implementation.
>
> Hmm, I don't think it's that premature; the C++ committee has been very
> serious about time-based releases every three years. I think it makes
> sense for the advertised flag to be c++2b, but let's also go ahead and
> add the c++23 flags as hidden, and use cxx23 internally.
Ok, I'll change from only exposing -std=c++2b to the end goal of
-std=c++23. You pointed out below a flaw in target-supports.exp.
Checking "make check-c++", I found that I'd also broken many tests
while adjusting c++2a to be c++20. I'll take the 2a->20 change out of
this patch. It can be in a separate patch. Seeing the cost of
changing from "2a" to "20", I'll post up patch v3 with support for
-std=c++23 so that a "2b->23" change isn't needed in a few years.
GCC's C++23 will still be experimental, despite the flag be
-std=c++23.
>
> > gcc/
> >
> > Add support for -std=c++2b
> > * doc/cpp.texi (__cplusplus): Document value for -std=c++2b
> > or -std=gnu++2b.
> > * doc/invoke.texi: Document -std=c++2b and -std=gnu++2b.
> >
> > gcc/c-family
> >
> > Add support for -std=c++2b
> > * c-common.h (cxx_dialect): Add cxx2b as a dialect.
> > * c.opt: Add options for -std=c++2b and -std=gnu++2b.
> > * c-opts.c (set_std_cxx2b): New.
> > (c_common_handle_option): Set options when -std=c++2b is enabled.
> > (c_common_post_options): Adjust comments.
> > (set_std_cxx20): Likewise.
> > * dwarf2out.c (highest_c_language): Recognise C++20 and C++23.
> > (gen_compile_unit_die): Recognise C++23.
>
> dwarf2out.c isn't in c-family.
>
> > gcc/testsuite
> >
> > Add support for -std=c++2b
> > * lib/target-supports.exp (check_effective_target_c++2a_only):
> > rename to check_effective_target_c++20_only.
> > (check_effective_target_c++2a): rename to check_effective_target_c++20.
> > (check_effective_target_c++20): Return 1
> > if check_effective_target_c++20_only or
> > if check_effective_target_c++2b.
> > (check_effective_target_c++20_down): New.
> > (check_effective_target_c++2a_only): New.
> > (check_effective_target_c++2a): New.
> > * g++.dg/cpp2b/cplusplus.C: New.
> >
> > libcpp
> > Add support for -std=c++2b
> > * include/cpplib.h (c_lang): Add CXX2B and GNUCXX2B.
> > * init.c (lang_defaults): Add rows for CXX2B and GNUCXX2B.
> > (cpp_init_builtins): Set __cplusplus to 202100L for C++2b.
> > ---
> > gcc/c-family/c-common.h | 4 ++-
> > gcc/c-family/c-opts.c | 29 ++++++++++++++++++++++--
> > gcc/c-family/c.opt | 8 ++++++
> > gcc/doc/cpp.texi | 7 +++--
> > gcc/doc/invoke.texi | 10 ++++++++
> > gcc/dwarf2out.c | 7 +++++
> > gcc/testsuite/g++.dg/cpp2b/cplusplus.C | 4 +++
> > gcc/testsuite/lib/target-supports.exp | 39
> > +++++++++++++++++++++++----------
> > libcpp/include/cpplib.h | 3 +-
> > libcpp/init.c | 7 +++++
> > 10 files changed, 98 insertions(+), 20 deletions(-)
> >
> > diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
> > index a65c78f7240..f562cdebf4c 100644
> > --- a/gcc/c-family/c-common.h
> > +++ b/gcc/c-family/c-common.h
> > @@ -738,7 +738,9 @@ enum cxx_dialect {
> > /* C++17 */
> > cxx17,
> > /* C++20 */
> > - cxx20
> > + cxx20,
> > + /* C++2b (C++23?) */
> > + cxx2b
> > };
> >
> > /* The C++ dialect being used. C++98 is the default. */
> > diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
> > index 3cdf41bc6e2..15f120d475d 100644
> > --- a/gcc/c-family/c-opts.c
> > +++ b/gcc/c-family/c-opts.c
> > @@ -113,6 +113,7 @@ static void set_std_cxx11 (int);
> > static void set_std_cxx14 (int);
> > static void set_std_cxx17 (int);
> > static void set_std_cxx20 (int);
> > +static void set_std_cxx2b (int);
> > static void set_std_c89 (int, int);
> > static void set_std_c99 (int);
> > static void set_std_c11 (int);
> > @@ -649,6 +650,12 @@ c_common_handle_option (size_t scode, const char
> > *arg, HOST_WIDE_INT value,
> > set_std_cxx20 (code == OPT_std_c__20 /* ISO */);
> > break;
> >
> > + case OPT_std_c__2b:
> > + case OPT_std_gnu__2b:
> > + if (!preprocessing_asm_p)
> > + set_std_cxx2b (code == OPT_std_c__2b /* ISO */);
> > + break;
> > +
> > case OPT_std_c90:
> > case OPT_std_iso9899_199409:
> > if (!preprocessing_asm_p)
> > @@ -1019,7 +1026,7 @@ c_common_post_options (const char **pfilename)
> > warn_narrowing = 1;
> >
> > /* Unless -f{,no-}ext-numeric-literals has been used explicitly,
> > - for -std=c++{11,14,17,2a} default to -fno-ext-numeric-literals. */
> > + for -std=c++{11,14,17,20,2b} default to -fno-ext-numeric-literals. */
> > if (flag_iso && !global_options_set.x_flag_ext_numeric_literals)
> > cpp_opts->ext_numeric_literals = 0;
> > }
> > @@ -1763,7 +1770,7 @@ set_std_cxx20 (int iso)
> > flag_no_gnu_keywords = iso;
> > flag_no_nonansi_builtin = iso;
> > flag_iso = iso;
> > - /* C++17 includes the C11 standard library. */
> > + /* C++20 includes the C11 standard library. */
> > flag_isoc94 = 1;
> > flag_isoc99 = 1;
> > flag_isoc11 = 1;
> > @@ -1773,6 +1780,24 @@ set_std_cxx20 (int iso)
> > lang_hooks.name = "GNU C++20";
> > }
> >
> > +/* Set the C++ 202b standard (without GNU extensions if ISO). */
> > +static void
> > +set_std_cxx2b (int iso)
> > +{
> > + cpp_set_lang (parse_in, iso ? CLK_CXX2B: CLK_GNUCXX2B);
> > + flag_no_gnu_keywords = iso;
> > + flag_no_nonansi_builtin = iso;
> > + flag_iso = iso;
> > + /* C++2b includes the C11 standard library. */
> > + flag_isoc94 = 1;
> > + flag_isoc99 = 1;
> > + flag_isoc11 = 1;
> > + /* C++2b includes coroutines. */
> > + flag_coroutines = true;
> > + cxx_dialect = cxx2b;
> > + lang_hooks.name = "GNU C++20"; /* Pretend C++20 until standardization.
> > */
> > +}
> > +
> > /* Args to -d specify what to dump. Silently ignore
> > unrecognized options; they may be aimed at toplev.c. */
> > static void
> > diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
> > index 1766364806e..273772a0cd5 100644
> > --- a/gcc/c-family/c.opt
> > +++ b/gcc/c-family/c.opt
> > @@ -2214,6 +2214,10 @@ std=c++20
> > C++ ObjC++
> > Conform to the ISO 2020 C++ draft standard (experimental and
> > incomplete support).
> >
> > +std=c++2b
> > +C++ ObjC++
> > +Conform to the ISO 2023(?) C++ draft standard (experimental and
> > incomplete support).
> > +
> > std=c11
> > C ObjC
> > Conform to the ISO 2011 C standard.
> > @@ -2292,6 +2296,10 @@ std=gnu++20
> > C++ ObjC++
> > Conform to the ISO 2020 C++ draft standard with GNU extensions
> > (experimental and incomplete support).
> >
> > +std=gnu++2b
> > +C++ ObjC++
> > +Conform to the ISO 2023(?) C++ draft standard with GNU extensions
> > (experimental and incomplete support).
> > +
> > std=gnu11
> > C ObjC
> > Conform to the ISO 2011 C standard with GNU extensions.
> > diff --git a/gcc/doc/cpp.texi b/gcc/doc/cpp.texi
> > index 25f2625d8bd..f801024affd 100644
> > --- a/gcc/doc/cpp.texi
> > +++ b/gcc/doc/cpp.texi
> > @@ -1907,9 +1907,10 @@ selected, the value of the macro is
> > @code{201103L} for the 2011 C++ standard,
> > @code{201402L} for the 2014 C++ standard,
> > @code{201703L} for the 2017 C++ standard,
> > -or an unspecified value strictly larger than @code{201703L} for the
> > -experimental languages enabled by @option{-std=c++2a} and
> > -@option{-std=gnu++2a}.
> > +@code{202002L} for the 2020 C++ standard,
> > +or an unspecified value strictly larger than @code{202002L} for the
> > +experimental languages enabled by @option{-std=c++2b} and
> > +@option{-std=gnu++2b}.
> >
> > @item __OBJC__
> > This macro is defined, with value 1, when the Objective-C compiler is in
> > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > index 226b8ade430..11a6e9a23c3 100644
> > --- a/gcc/doc/invoke.texi
> > +++ b/gcc/doc/invoke.texi
> > @@ -2430,6 +2430,16 @@ GNU dialect of @option{-std=c++20}.
> > Support is experimental, and could change in incompatible ways in
> > future releases.
> > The name @samp{gnu++2a} is deprecated.
> > +
> > +@item c++2b
> > +The next revision of the ISO C++ standard, planned for
> > +2023. Support is highly experimental, and will almost certainly
> > +change in incompatible ways in future releases.
> > +
> > +@item gnu++2b
> > +GNU dialect of @option{-std=c++2b}. Support is highly experimental,
> > +and will almost certainly change in incompatible ways in future
> > +releases.
> > @end table
> >
> > @item -fgnu89-inline
> > diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
> > index 8b6890a5097..97df6604373 100644
> > --- a/gcc/dwarf2out.c
> > +++ b/gcc/dwarf2out.c
> > @@ -24445,6 +24445,10 @@ static char *producer_string;
> > static const char *
> > highest_c_language (const char *lang1, const char *lang2)
> > {
> > + if (strcmp ("GNU C++23", lang1) == 0 || strcmp ("GNU C++23", lang2) == 0)
> > + return "GNU C++23";
> > + if (strcmp ("GNU C++20", lang1) == 0 || strcmp ("GNU C++20", lang2) == 0)
> > + return "GNU C++20";
> > if (strcmp ("GNU C++17", lang1) == 0 || strcmp ("GNU C++17", lang2) ==
> > 0)
> > return "GNU C++17";
> > if (strcmp ("GNU C++14", lang1) == 0 || strcmp ("GNU C++14", lang2) ==
> > 0)
> > @@ -24550,7 +24554,8 @@ gen_compile_unit_die (const char *filename)
> > else if (strcmp (language_string, "GNU C++14") == 0)
> > language = DW_LANG_C_plus_plus_14;
> > else if (strcmp (language_string, "GNU C++17") == 0
> > - || strcmp (language_string, "GNU C++20") == 0)
> > + || strcmp (language_string, "GNU C++20") == 0
> > + || strcmp (language_string, "GNU C++23") == 0)
> > /* For now. */
> > language = DW_LANG_C_plus_plus_14;
> > }
> > diff --git a/gcc/testsuite/g++.dg/cpp2b/cplusplus.C
> > b/gcc/testsuite/g++.dg/cpp2b/cplusplus.C
> > new file mode 100644
> > index 00000000000..615d9f081de
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp2b/cplusplus.C
> > @@ -0,0 +1,4 @@
> > +// { dg-do compile }
> > +// { dg-options "-std=c++2b" }
> > +
> > +static_assert(__cplusplus > 202002L);
> > diff --git a/gcc/testsuite/lib/target-supports.exp
> > b/gcc/testsuite/lib/target-supports.exp
> > index 5cf0f4218a6..31be4de12a5 100644
> > --- a/gcc/testsuite/lib/target-supports.exp
> > +++ b/gcc/testsuite/lib/target-supports.exp
> > @@ -9434,7 +9434,6 @@ proc check_effective_target_c++14_only { } {
> > }
> > return 0
> > }
> > -
> > proc check_effective_target_c++14 { } {
> > if [check_effective_target_c++14_only] {
> > return 1
> > @@ -9475,7 +9474,6 @@ proc check_effective_target_c++17_only { } {
> > }
> > return 0
> > }
> > -
> > proc check_effective_target_c++17 { } {
> > if [check_effective_target_c++17_only] {
> > return 1
> > @@ -9489,12 +9487,12 @@ proc check_effective_target_c++17_down { } {
> > return [expr ![check_effective_target_c++2a] ]
> > }
> >
> > -proc check_effective_target_c++2a_only { } {
> > +proc check_effective_target_c++20_only { } {
> > global cxx_default
> > if ![check_effective_target_c++] {
> > return 0
> > }
> > - if [check-flags { { } { } { -std=c++2a -std=gnu++2a -std=c++20
> > -std=gnu++20 } }] {
> > + if [check-flags { { } { } { -std=c++20 -std=gnu++20 -std=c++2a
> > -std=gnu++2a } }] {
> > return 1
> > }
> > if { $cxx_default == "c++20" && [check-flags { { } { } { } {
> > -std=* } }] } {
> > @@ -9502,18 +9500,37 @@ proc check_effective_target_c++2a_only { } {
> > }
> > return 0
> > }
> > -proc check_effective_target_c++2a { } {
> > - return [check_effective_target_c++2a_only]
> > +proc check_effective_target_c++20 { } {
> > + if [check_effective_target_c++20_only] {
> > + return 1
> > + }
> > + return [check_effective_target_c++2b]
> > }
> > -
> > -proc check_effective_target_c++20_only { } {
> > - return [check_effective_target_c++2a_only]
> > +proc check_effective_target_c++20_down { } {
> > + if ![check_effective_target_c++] {
> > + return 0
> > + }
> > + return [expr ![check_effective_target_c++20] ]
>
> This should be !c++2b.
Indeed, thanks for highlighting my mistake.
>
> > }
> >
> > -proc check_effective_target_c++20 { } {
> > - return [check_effective_target_c++2a]
> > +proc check_effective_target_c++2b_only { } {
> > + global cxx_default
> > + if ![check_effective_target_c++] {
> > + return 0
> > + }
> > + if [check-flags { { } { } { -std=c++2b -std=gnu++2b } }] {
> > + return 1
> > + }
> > + if { $cxx_default == "c++23" && [check-flags { { } { } { } {
> > -std=* } }] } {
> > + return 1
> > + }
> > + return 0
> > +}
> > +proc check_effective_target_c++2b { } {
> > + return [check_effective_target_c++2b_only]
> > }
> >
> > +
> > # Check for C++ Concepts support, i.e. -fconcepts flag.
> > proc check_effective_target_concepts { } {
> > if [check_effective_target_c++2a] {
> > diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
> > index bcc50ba45f6..c213fbac0b1 100644
> > --- a/libcpp/include/cpplib.h
> > +++ b/libcpp/include/cpplib.h
> > @@ -173,7 +173,8 @@ enum c_lang {CLK_GNUC89 = 0, CLK_GNUC99,
> > CLK_GNUC11, CLK_GNUC17, CLK_GNUC2X,
> > CLK_STDC2X,
> > CLK_GNUCXX, CLK_CXX98, CLK_GNUCXX11, CLK_CXX11,
> > CLK_GNUCXX14, CLK_CXX14, CLK_GNUCXX17, CLK_CXX17,
> > - CLK_GNUCXX20, CLK_CXX20, CLK_ASM};
> > + CLK_GNUCXX20, CLK_CXX20, CLK_GNUCXX2B, CLK_CXX2B,
> > + CLK_ASM};
> >
> > /* Payload of a NUMBER, STRING, CHAR or COMMENT token. */
> > struct GTY(()) cpp_string {
> > diff --git a/libcpp/init.c b/libcpp/init.c
> > index a5103c4d454..80543f90a51 100644
> > --- a/libcpp/init.c
> > +++ b/libcpp/init.c
> > @@ -119,6 +119,8 @@ static const struct lang_flags lang_defaults[] =
> > /* CXX17 */ { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
> > 1, 0, 1, 0, 1, 0 },
> > /* GNUCXX20 */ { 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1,
> > 1, 0, 1, 1, 1, 0 },
> > /* CXX20 */ { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
> > 1, 0, 1, 1, 1, 0 },
> > + /* GNUCXX2B */ { 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1,
> > 1, 0, 1, 1, 1, 0 },
> > + /* CXX2B */ { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
> > 1, 0, 1, 1, 1, 0 },
> > /* ASM */ { 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0,
> > 0, 0, 0, 0, 0, 0 }
> > };
> >
> > @@ -540,7 +542,10 @@ cpp_init_builtins (cpp_reader *pfile, int hosted)
> >
> > if (CPP_OPTION (pfile, cplusplus))
> > {
> > - if (CPP_OPTION (pfile, lang) == CLK_CXX20
> > + if (CPP_OPTION (pfile, lang) == CLK_CXX2B
> > + || CPP_OPTION (pfile, lang) == CLK_GNUCXX2B)
> > + _cpp_define_builtin (pfile, "__cplusplus 202100L");
>
> Let's add a comment here.
>
> > + else if (CPP_OPTION (pfile, lang) == CLK_CXX20
> > || CPP_OPTION (pfile, lang) == CLK_GNUCXX20)
> > _cpp_define_builtin (pfile, "__cplusplus 202002L");
> > else if (CPP_OPTION (pfile, lang) == CLK_CXX17
> >
>
> Jason
>
