[PATCH v2] c++: Add support for -std=c++2b
Jason Merrill
jason@redhat.com
Tue Jan 19 23:28:45 GMT 2021
On 1/10/21 7:28 PM, Paul Fee via Gcc-patches wrote:
> [PATCH v2] c++: Add support for -std=c++2b
Thanks!
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> 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.
> 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.
> }
>
> -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
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