[PATCH] Begin implementing Plan 9 C extensions.

[David Majnemer]

On Tue, May 20, 2014 at 2:25 PM, Alp Toker <alp at nuanti.com> wrote:

> Hi
>
> Is this http://plan9.bell-labs.com/sys/doc/compiler.html ?
>
> Looks like there's a fair bit of ground to cover to support this in clang.
>
> Some extensions like unnamed substructures could borrow from
> -fms-extensions but others like structure displays and initialization
> indexes would appear to require new parse rules and semantic analysis.
>

Structure displays are pretty much identical to C99's compound literals.
Initialization indexes aren't too far from C99 designated initializers at
all. The only difference I can see is that initialization indexes don't
have an equals token between the index and the initializer.


>
> How many active projects out there are actually using this language mode?
> There doesn't appear to be much recent (< 24 years old) material on the
> language online.
>
> Alp.
>
>
>
>
> On 20/05/2014 23:59, Peter Collingbourne wrote:
>
>> This makes a start on implementing a number of extensions provided by the
>> Plan
>> 9 C compiler, from which Go's "cc" C compiler is derived. These extensions
>> are required for building some parts of the Go standard library.
>>
>> This patch introduces the -fplan9-extensions flag and causes it to enable
>> an extension which allows typedefs to be declared multiple times.
>>
>> http://reviews.llvm.org/D3853
>>
>> Files:
>>    include/clang/Basic/LangOptions.def
>>    include/clang/Driver/Options.td
>>    lib/Driver/Tools.cpp
>>    lib/Frontend/CompilerInvocation.cpp
>>    lib/Sema/SemaDecl.cpp
>>    test/Sema/c11-typedef-redef.c
>>
>> Index: include/clang/Basic/LangOptions.def
>> ===================================================================
>> --- include/clang/Basic/LangOptions.def
>> +++ include/clang/Basic/LangOptions.def
>> @@ -47,6 +47,7 @@
>>   LANGOPT(MicrosoftExt      , 1, 0, "Microsoft C++ extensions")
>>   LANGOPT(AsmBlocks         , 1, 0, "Microsoft inline asm blocks")
>>   LANGOPT(Borland           , 1, 0, "Borland extensions")
>> +LANGOPT(Plan9Ext          , 1, 0, "Plan 9 extensions")
>>   LANGOPT(CPlusPlus         , 1, 0, "C++")
>>   LANGOPT(CPlusPlus11       , 1, 0, "C++11")
>>   LANGOPT(CPlusPlus1y       , 1, 0, "C++1y")
>> Index: include/clang/Driver/Options.td
>> ===================================================================
>> --- include/clang/Driver/Options.td
>> +++ include/clang/Driver/Options.td
>> @@ -775,6 +775,8 @@
>>   def fno_pic : Flag<["-"], "fno-pic">, Group<f_Group>;
>>   def fpie : Flag<["-"], "fpie">, Group<f_Group>;
>>   def fno_pie : Flag<["-"], "fno-pie">, Group<f_Group>;
>> +def fplan9_extensions : Flag<["-"], "fplan9-extensions">,
>> Group<f_Group>, Flags<[CC1Option]>;
>> +def fno_plan9_extensions : Flag<["-"], "fno-plan9-extensions">,
>> Group<f_Group>;
>>   def fprofile_arcs : Flag<["-"], "fprofile-arcs">, Group<f_Group>;
>>   def fprofile_generate : Flag<["-"], "fprofile-generate">,
>> Group<f_Group>;
>>   def framework : Separate<["-"], "framework">, Flags<[LinkerInput]>;
>> Index: lib/Driver/Tools.cpp
>> ===================================================================
>> --- lib/Driver/Tools.cpp
>> +++ lib/Driver/Tools.cpp
>> @@ -3678,6 +3678,11 @@
>>                      options::OPT_fno_borland_extensions, false))
>>       CmdArgs.push_back("-fborland-extensions");
>>   +  // -fno-plan9-extensions is default.
>> +  if (Args.hasFlag(options::OPT_fplan9_extensions,
>> +                   options::OPT_fno_plan9_extensions, false))
>> +    CmdArgs.push_back("-fplan9-extensions");
>> +
>>     // -fno-delayed-template-parsing is default, except for Windows where
>> MSVC STL
>>     // needs it.
>>     if (Args.hasFlag(options::OPT_fdelayed_template_parsing,
>> Index: lib/Frontend/CompilerInvocation.cpp
>> ===================================================================
>> --- lib/Frontend/CompilerInvocation.cpp
>> +++ lib/Frontend/CompilerInvocation.cpp
>> @@ -1351,6 +1351,7 @@
>>     Opts.MSCVersion = getLastArgIntValue(Args, OPT_fmsc_version, 0,
>> Diags);
>>     Opts.VtorDispMode = getLastArgIntValue(Args, OPT_vtordisp_mode_EQ, 1,
>> Diags);
>>     Opts.Borland = Args.hasArg(OPT_fborland_extensions);
>> +  Opts.Plan9Ext = Args.hasArg(OPT_fplan9_extensions);
>>     Opts.WritableStrings = Args.hasArg(OPT_fwritable_strings);
>>     Opts.ConstStrings = Args.hasFlag(OPT_fconst_strings,
>> OPT_fno_const_strings,
>>                                      Opts.ConstStrings);
>> Index: lib/Sema/SemaDecl.cpp
>> ===================================================================
>> --- lib/Sema/SemaDecl.cpp
>> +++ lib/Sema/SemaDecl.cpp
>> @@ -1769,8 +1769,8 @@
>>       return New->setInvalidDecl();
>>     }
>>   -  // Modules always permit redefinition of typedefs, as does C11.
>> -  if (getLangOpts().Modules || getLangOpts().C11)
>> +  // Modules always permit redefinition of typedefs, as does C11 and
>> Plan 9.
>> +  if (getLangOpts().Modules || getLangOpts().C11 ||
>> getLangOpts().Plan9Ext)
>>       return;
>>         // If we have a redefinition of a typedef in C, emit a warning.
>>  This warning
>> Index: test/Sema/c11-typedef-redef.c
>> ===================================================================
>> --- test/Sema/c11-typedef-redef.c
>> +++ test/Sema/c11-typedef-redef.c
>> @@ -1,4 +1,5 @@
>>   // RUN: %clang_cc1 -std=c11 %s -verify
>> +// RUN: %clang_cc1 -fplan9-extensions %s -verify
>>     typedef int type;
>>   typedef type type;
>>
>>
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>>
>
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