On Thu, 21 Nov 2024, Jakub Jelinek wrote:
> Hi!
>
> DWARF now maintains DW_LANG_* code assignment online and 27 language codes
> have been assigned already after DWARF 5 has been released, see
> https://dwarfstd.org/languages.html
> including one added yesterday (DW_LANG_C23).
> DWARF 6 plans to use something different, DW_AT_language_{name,version}
> pair where the new language versions will be just dealt with automatically
> rather than adding new codes, say for C23 we'll be able to use
> DW_LNAME_C 202311 while for C2Y for now to use
> DW_LNAME_C 202500 until the standard is finalized.
>
> Now, the question is whether the toolchain should use those post DWARF 5
> codes for -gdwarf-5 -gno-strict-dwarf, or if we'll just ignore those
> and only switch to DWARF 6 stuff when the standard is released and people
> use -gdwarf-6 (or when we switch over to that as default).
>
> The following patch starts using those new codes (just for C/C++ for now,
> Ada/Fortran not switched, Ada because I'm really not familiar with Ada and
> Fortran because it doesn't say 2018 in the language string).
>
> The problem with the patch is that it regresses quite a few tests,
> in particular
> gcc.dg/guality/pr78726.c
> g++.dg/guality/redeclaration1.C
> libstdc++-prettyprinters/*.cc
> libstdc++-xmethods/deque.cc
> because my gdb doesn't handle those (but git trunk gdb doesn't either),
> so for those the new codes are just unknown languages rather than newer
> revisions of C or C++.
> From what I can read in gdb, it doesn't seem to care about exact standard
> revision, all it cares about is if the TU is C, C++, Fortran, Ada etc.
> So, from this POV perhaps we shouldn't switch at all and ignore all the
> post-DWARF 5 codes.
> Or shall we wait until gdb, elfutils, whatever else actually looks at
> DW_AT_language values is changed to handle the new codes and apply this
> patch after that (still one would need a new version of gdb/elfutils/etc.)?
> Or wait say half a year or year after that support is added in the
> consumers?
I'd say we at least wait until some consumers have support, if it
regresses behavior with "older" consumers I don't think we want to
have this as default for now anyway.
Richard.
> The DWARF 6 planned scheme was designed exactly to overcome this problem,
> consumers that only care if something is C or C++ etc. will be able to
> hardcode the code once and if they care for some behavior on something
> more specific, they can just compare the version, DW_AT_language_version >=
> 201703 for C++ (or < etc.), or for Fortran DW_AT_language_version >= 2008,
> ...
>
> 2024-11-21 Jakub Jelinek <ja...@redhat.com>
>
> gcc/
> * dwarf2out.cc (is_c): Handle also DW_LANG_C{17,23}.
> (is_cxx): Handle also DW_LANG_C_plus_plus_{17,20,23}.
> (is_fortran): Handle also DW_LANG_Fortran18.
> (is_ada): Handle also DW_LANG_Ada20{05,12}.
> (lower_bound_default): Handle also
> DW_LANG_{C{17,23},C_plus_plus_{17,20,23},Fortran18,Ada20{05,12}}.
> (add_prototyped_attribute): Handle DW_LANG_C{17,23}.
> (gen_compile_unit_die): Use DW_LANG_C17 if not -gstrict-dwarf
> for C17. Use DW_LANG_C23 if not -gstrict-dwarf for C23/C2Y. Use
> DW_LANG_C_plus_plus_{17,20,23} if not -gstrict-dwarf for C++{17,20,23}
> and the last one also for C++26. Handle DW_LANG_Fortran18.
> include/
> * g++.dg/debug/dwarf2/lang-cpp17.C: Add -gno-strict-dwarf to
> dg-options and expect different DW_AT_language value.
> * g++.dg/debug/dwarf2/lang-cpp20.C: Likewise.
> * g++.dg/debug/dwarf2/lang-cpp23.C: New test.
>
> --- gcc/dwarf2out.cc.jj 2024-10-25 10:00:29.445768186 +0200
> +++ gcc/dwarf2out.cc 2024-11-20 21:49:48.237062064 +0100
> @@ -5540,7 +5540,8 @@ is_c (void)
> unsigned int lang = get_AT_unsigned (comp_unit_die (), DW_AT_language);
>
> return (lang == DW_LANG_C || lang == DW_LANG_C89 || lang == DW_LANG_C99
> - || lang == DW_LANG_C11 || lang == DW_LANG_ObjC);
> + || lang == DW_LANG_C11 || lang == DW_LANG_C17 || lang == DW_LANG_C23
> + || lang == DW_LANG_ObjC);
>
>
> }
> @@ -5553,7 +5554,9 @@ is_cxx (void)
> unsigned int lang = get_AT_unsigned (comp_unit_die (), DW_AT_language);
>
> return (lang == DW_LANG_C_plus_plus || lang == DW_LANG_ObjC_plus_plus
> - || lang == DW_LANG_C_plus_plus_11 || lang == DW_LANG_C_plus_plus_14);
> + || lang == DW_LANG_C_plus_plus_11 || lang == DW_LANG_C_plus_plus_14
> + || lang == DW_LANG_C_plus_plus_17 || lang == DW_LANG_C_plus_plus_20
> + || lang == DW_LANG_C_plus_plus_23);
> }
>
> /* Return TRUE if DECL was created by the C++ frontend. */
> @@ -5581,7 +5584,8 @@ is_fortran (void)
> || lang == DW_LANG_Fortran90
> || lang == DW_LANG_Fortran95
> || lang == DW_LANG_Fortran03
> - || lang == DW_LANG_Fortran08);
> + || lang == DW_LANG_Fortran08
> + || lang == DW_LANG_Fortran18);
> }
>
> static inline bool
> @@ -5617,7 +5621,8 @@ is_ada (void)
> {
> unsigned int lang = get_AT_unsigned (comp_unit_die (), DW_AT_language);
>
> - return lang == DW_LANG_Ada95 || lang == DW_LANG_Ada83;
> + return (lang == DW_LANG_Ada95 || lang == DW_LANG_Ada83
> + || lang == DW_LANG_Ada2005 || lang == DW_LANG_Ada2012);
> }
>
> /* Return TRUE if the language is D. */
> @@ -21645,9 +21650,14 @@ lower_bound_default (void)
> case DW_LANG_C89:
> case DW_LANG_C99:
> case DW_LANG_C11:
> + case DW_LANG_C17:
> + case DW_LANG_C23:
> case DW_LANG_C_plus_plus:
> case DW_LANG_C_plus_plus_11:
> case DW_LANG_C_plus_plus_14:
> + case DW_LANG_C_plus_plus_17:
> + case DW_LANG_C_plus_plus_20:
> + case DW_LANG_C_plus_plus_23:
> case DW_LANG_ObjC:
> case DW_LANG_ObjC_plus_plus:
> return 0;
> @@ -21656,13 +21666,16 @@ lower_bound_default (void)
> case DW_LANG_Fortran95:
> case DW_LANG_Fortran03:
> case DW_LANG_Fortran08:
> + case DW_LANG_Fortran18:
> return 1;
> case DW_LANG_UPC:
> case DW_LANG_D:
> case DW_LANG_Python:
> return dwarf_version >= 4 ? 0 : -1;
> - case DW_LANG_Ada95:
> case DW_LANG_Ada83:
> + case DW_LANG_Ada95:
> + case DW_LANG_Ada2005:
> + case DW_LANG_Ada2012:
> case DW_LANG_Cobol74:
> case DW_LANG_Cobol85:
> case DW_LANG_Modula2:
> @@ -22025,6 +22038,8 @@ add_prototyped_attribute (dw_die_ref die
> case DW_LANG_C89:
> case DW_LANG_C99:
> case DW_LANG_C11:
> + case DW_LANG_C17:
> + case DW_LANG_C23:
> case DW_LANG_ObjC:
> if (prototype_p (func_type))
> add_AT_flag (die, DW_AT_prototyped, 1);
> @@ -25372,11 +25387,17 @@ gen_compile_unit_die (const char *filena
> language = DW_LANG_C99;
>
> if (dwarf_version >= 5 /* || !dwarf_strict */)
> - if (strcmp (language_string, "GNU C11") == 0
> - || strcmp (language_string, "GNU C17") == 0
> - || strcmp (language_string, "GNU C23") == 0
> - || strcmp (language_string, "GNU C2Y") == 0)
> - language = DW_LANG_C11;
> + {
> + if (strcmp (language_string, "GNU C11") == 0)
> + language = DW_LANG_C11;
> + else if (strcmp (language_string, "GNU C17") == 0)
> + language = DW_LANG_C17;
> + else if (strcmp (language_string, "GNU C23") == 0
> + || strcmp (language_string, "GNU C2Y") == 0)
> + language = DW_LANG_C23;
> + if (dwarf_strict && language > DW_LANG_C11)
> + language = DW_LANG_C11;
> + }
> }
> }
> else if (startswith (language_string, "GNU C++"))
> @@ -25388,11 +25409,14 @@ gen_compile_unit_die (const char *filena
> language = DW_LANG_C_plus_plus_11;
> 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++23") == 0
> + else if (strcmp (language_string, "GNU C++17") == 0)
> + language = DW_LANG_C_plus_plus_17;
> + else if (strcmp (language_string, "GNU C++20") == 0)
> + language = DW_LANG_C_plus_plus_20;
> + else if (strcmp (language_string, "GNU C++23") == 0
> || strcmp (language_string, "GNU C++26") == 0)
> - /* For now. */
> + language = DW_LANG_C_plus_plus_23;
> + if (dwarf_strict && language > DW_LANG_C_plus_plus_14)
> language = DW_LANG_C_plus_plus_14;
> }
> }
> @@ -25445,6 +25469,7 @@ gen_compile_unit_die (const char *filena
> case DW_LANG_Fortran95:
> case DW_LANG_Fortran03:
> case DW_LANG_Fortran08:
> + case DW_LANG_Fortran18:
> /* Fortran has case insensitive identifiers and the front-end
> lowercases everything. */
> add_AT_unsigned (die, DW_AT_identifier_case, DW_ID_down_case);
> --- gcc/testsuite/g++.dg/debug/dwarf2/lang-cpp17.C.jj 2021-01-18
> 14:52:42.946040137 +0100
> +++ gcc/testsuite/g++.dg/debug/dwarf2/lang-cpp17.C 2024-11-21
> 09:08:09.868183593 +0100
> @@ -1,8 +1,7 @@
> // { dg-do compile }
> // { dg-options "-O -std=c++17 -gdwarf-5 -dA -gno-strict-dwarf" }
> // { dg-skip-if "AIX DWARF5" { powerpc-ibm-aix* } }
> -// For -gdwarf-6 hopefully DW_LANG_C_plus_plus_17
> -// DW_LANG_C_plus_plus_14 = 0x0021
> -// { dg-final { scan-assembler "0x21\[^\n\r]* DW_AT_language" } } */
> +// DW_LANG_C_plus_plus_177 = 0x002a
> +// { dg-final { scan-assembler "0x2a\[^\n\r]* DW_AT_language" } } */
>
> int version;
> --- gcc/testsuite/g++.dg/debug/dwarf2/lang-cpp20.C.jj 2021-01-18
> 14:52:42.946040137 +0100
> +++ gcc/testsuite/g++.dg/debug/dwarf2/lang-cpp20.C 2024-11-21
> 09:08:31.391877872 +0100
> @@ -1,8 +1,7 @@
> // { dg-do compile }
> // { dg-options "-O -std=c++20 -gdwarf-5 -dA -gno-strict-dwarf" }
> // { dg-skip-if "AIX DWARF5" { powerpc-ibm-aix* } }
> -// For -gdwarf-6 hopefully DW_LANG_C_plus_plus_20
> -// DW_LANG_C_plus_plus_14 = 0x0021
> -// { dg-final { scan-assembler "0x21\[^\n\r]* DW_AT_language" } } */
> +// DW_LANG_C_plus_plus_20 = 0x002b
> +// { dg-final { scan-assembler "0x2b\[^\n\r]* DW_AT_language" } } */
>
> int version;
> --- gcc/testsuite/g++.dg/debug/dwarf2/lang-cpp23.C.jj 2024-11-21
> 09:08:41.801729997 +0100
> +++ gcc/testsuite/g++.dg/debug/dwarf2/lang-cpp23.C 2024-11-21
> 09:08:57.226510904 +0100
> @@ -0,0 +1,7 @@
> +// { dg-do compile }
> +// { dg-options "-O -std=c++23 -gdwarf-5 -dA -gno-strict-dwarf" }
> +// { dg-skip-if "AIX DWARF5" { powerpc-ibm-aix* } }
> +// DW_LANG_C_plus_plus_23 = 0x003a
> +// { dg-final { scan-assembler "0x3a\[^\n\r]* DW_AT_language" } } */
> +
> +int version;
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
