r274991 - [clang-cl] Add support for /Zd

David Majnemer via cfe-commits cfe-commits at lists.llvm.org
Mon Jul 11 09:19:08 PDT 2016 

On Mon, Jul 11, 2016 at 9:03 AM, Nico Weber <thakis at chromium.org> wrote:

> On Mon, Jul 11, 2016 at 11:51 AM, David Majnemer <david.majnemer at gmail.com
> > wrote:
>
>>
>>
>> On Mon, Jul 11, 2016 at 8:42 AM, Nico Weber <thakis at chromium.org> wrote:
>>
>>> On Mon, Jul 11, 2016 at 11:36 AM, David Majnemer <
>>> david.majnemer at gmail.com> wrote:
>>>
>>>>
>>>>
>>>> On Mon, Jul 11, 2016 at 7:18 AM, Nico Weber <thakis at chromium.org>
>>>> wrote:
>>>>
>>>>> VS2013's cl.exe doesn't understand /Zd, 2015's doesn't either. This
>>>>> means people who want to ask clang-cl for line tables only will have to add
>>>>> this flag in some if(is_clang) block in their build file anyways. What's
>>>>> the advantage of giving this flag a spelling that's different from both cl
>>>>> and clang? With -gline-tables-only, an if(is_clang) works on Linux, Mac,
>>>>> Windows.
>>>>>
>>>>> (Even if there's a good case for /Zd, I don't think we should remove
>>>>> user-exposed flags without a strong reason, so even if we keep /Zd I think
>>>>> we should also keep exposing -gline-tables-only.)
>>>>>
>>>>
>>>> Existing users of -gline-tables-only?  I'd imagine any responsible
>>>> users of -gline-tables-only would probably use their build system to verify
>>>> that the flag exists.  We have never released an official LLVM which
>>>> supported it (LLVM 3.8 came out in early March and -gline-tables-only was
>>>> exposed via clang-cl in mid March).
>>>>
>>>
>>> Ok, but why is /Zd better than -gline-tables-only?
>>>
>>
>> I see a few reasons:
>> - It is less surprising for a debug flag in the cl world to be called
>> /Zsomething instead of -gsomething.
>>
>
> Eh, you'll have to look it up either way to find the flag.
>

I agree.


> And when seeing the flag, the -g flag is more self-explanatory.
>

I disagree, I had no idea what that flag did until I started working on
debug info.


> Also, it is surprising that a clang-cl /-style flag doesn't work with cl,
> so it just moves the surprise around a bit.
>

It is surprising when that happens in either direction.  If this is
considered a bug, we will never "fix" it.


>
>
>> - I think that avoiding invasion of their namespace, when possible, is a
>> good thing.  It makes it less likely that we will conflict with a flag they
>> want to add in the future.
>>
>
> I don't understand this point. Doesn't invading their namespace make
> collisions _more_ likely?
>
>
>> - I imagine that if they wanted to add support back for
>> -gline-tables-only, they'd name it /Zd.
>>
>
> Given they had this flag and removed it, they probably didn't like it very
> much :-)
>
>
>> I'm sympathetic to the argument that "-gline-tables-only" is more
>> familiar to Linux/Mac OS X folks and that /Zd won't work across all
>> platforms.
>>
>> Here why I think that's ok:
>> - This is not really a new problem.  If you want to select c++1z you get
>> to spell it /std:c++latest for clang-cl and -std=c++14.
>>
>
> Sure, but these are flags that clang/gcc and cl interpret. So if you have
> a gcc build and a visual studio build, it's fairly easy to get each going
> with clang / clang-cl.
>
> With /Zd, we're needlessly inventing a new spelling for an existing clang
> flag.
>

icl also supports /Zd.


> As far as I can see, the new name creates a (small) problem without
> solving one.
>

This is an attempt to reduce unneeded diversity.


>
> So far, when we wanted to add a flag that cl doesn't have and that clang
> has, we've always gone for the clang spelling of that flag. That seems like
> a good guideline to me.
>

Often but not always.  For example, we have /Qvec instead of -fvectorize
because icl has the flag.


>
>
>> - People who want harmony between Mac OS X, Linux and Windows on the
>> driver side can just use clang++.
>>
>>
>>>
>>>
>>>>
>>>> I'd consider it in poor form for users to take a hard dependency on a
>>>> flag which only exists in a compiler which has never been released.
>>>>
>>>> I'd agree with you if -gline-tables-only had made its way to an actual
>>>> release.
>>>>
>>>>
>>>>>
>>>>> On Mon, Jul 11, 2016 at 10:08 AM, Nico Weber <thakis at chromium.org>
>>>>> wrote:
>>>>>
>>>>>> This breaks existing users of -gline-tables-only. What's the
>>>>>> motivation for this change?
>>>>>>
>>>>>
>>>>>> On Sat, Jul 9, 2016 at 5:49 PM, David Majnemer via cfe-commits <
>>>>>> cfe-commits at lists.llvm.org> wrote:
>>>>>>
>>>>>>> Author: majnemer
>>>>>>> Date: Sat Jul  9 16:49:16 2016
>>>>>>> New Revision: 274991
>>>>>>>
>>>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=274991&view=rev
>>>>>>> Log:
>>>>>>> [clang-cl] Add support for /Zd
>>>>>>>
>>>>>>> MASM (ML.exe and ML64.exe) and older versions of MSVC (CL.exe)
>>>>>>> support a
>>>>>>> flag called /Zd which is more-or-less -gline-tables-only.
>>>>>>>
>>>>>>> It seems nicer to support this flag instead of exposing
>>>>>>> -gline-tables-only.
>>>>>>>
>>>>>>> Modified:
>>>>>>>     cfe/trunk/include/clang/Driver/CLCompatOptions.td
>>>>>>>     cfe/trunk/include/clang/Driver/Options.td
>>>>>>>     cfe/trunk/lib/Driver/Tools.cpp
>>>>>>>     cfe/trunk/test/Driver/cl-options.c
>>>>>>>
>>>>>>> Modified: cfe/trunk/include/clang/Driver/CLCompatOptions.td
>>>>>>> URL:
>>>>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Driver/CLCompatOptions.td?rev=274991&r1=274990&r2=274991&view=diff
>>>>>>>
>>>>>>> ==============================================================================
>>>>>>> --- cfe/trunk/include/clang/Driver/CLCompatOptions.td (original)
>>>>>>> +++ cfe/trunk/include/clang/Driver/CLCompatOptions.td Sat Jul  9
>>>>>>> 16:49:16 2016
>>>>>>> @@ -166,6 +166,8 @@ def _SLASH_Zc_trigraphs_off : CLFlag<"Zc
>>>>>>>    HelpText<"Disable trigraphs (default)">, Alias<fno_trigraphs>;
>>>>>>>  def _SLASH_Z7 : CLFlag<"Z7">,
>>>>>>>    HelpText<"Enable CodeView debug information in object files">;
>>>>>>> +def _SLASH_Zd : CLFlag<"Zd">,
>>>>>>> +  HelpText<"Emit debug line number tables only">;
>>>>>>>  def _SLASH_Zi : CLFlag<"Zi">, Alias<_SLASH_Z7>,
>>>>>>>    HelpText<"Alias for /Z7. Does not produce PDBs.">;
>>>>>>>  def _SLASH_Zp : CLJoined<"Zp">,
>>>>>>>
>>>>>>> Modified: cfe/trunk/include/clang/Driver/Options.td
>>>>>>> URL:
>>>>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Driver/Options.td?rev=274991&r1=274990&r2=274991&view=diff
>>>>>>>
>>>>>>> ==============================================================================
>>>>>>> --- cfe/trunk/include/clang/Driver/Options.td (original)
>>>>>>> +++ cfe/trunk/include/clang/Driver/Options.td Sat Jul  9 16:49:16
>>>>>>> 2016
>>>>>>> @@ -1229,7 +1229,7 @@ def fdebug_prefix_map_EQ
>>>>>>>  def g_Flag : Flag<["-"], "g">, Group<g_Group>,
>>>>>>>    HelpText<"Generate source-level debug information">;
>>>>>>>  def gline_tables_only : Flag<["-"], "gline-tables-only">,
>>>>>>> Group<gN_Group>,
>>>>>>> -  Flags<[CoreOption]>, HelpText<"Emit debug line number tables
>>>>>>> only">;
>>>>>>> +  HelpText<"Emit debug line number tables only">;
>>>>>>>  def gmlt : Flag<["-"], "gmlt">, Alias<gline_tables_only>;
>>>>>>>  def g0 : Flag<["-"], "g0">, Group<gN_Group>;
>>>>>>>  def g1 : Flag<["-"], "g1">, Group<gN_Group>,
>>>>>>> Alias<gline_tables_only>;
>>>>>>>
>>>>>>> Modified: cfe/trunk/lib/Driver/Tools.cpp
>>>>>>> URL:
>>>>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/Tools.cpp?rev=274991&r1=274990&r2=274991&view=diff
>>>>>>>
>>>>>>> ==============================================================================
>>>>>>> --- cfe/trunk/lib/Driver/Tools.cpp (original)
>>>>>>> +++ cfe/trunk/lib/Driver/Tools.cpp Sat Jul  9 16:49:16 2016
>>>>>>> @@ -6269,12 +6269,18 @@ void Clang::AddClangCLArgs(const ArgList
>>>>>>>
>>>>>>>  CmdArgs.push_back(Args.MakeArgString(Twine(LangOptions::SSPStrong)));
>>>>>>>    }
>>>>>>>
>>>>>>> -  // Emit CodeView if -Z7 is present.
>>>>>>> -  *EmitCodeView = Args.hasArg(options::OPT__SLASH_Z7);
>>>>>>> -  if (*EmitCodeView)
>>>>>>> -    *DebugInfoKind = codegenoptions::LimitedDebugInfo;
>>>>>>> -  if (*EmitCodeView)
>>>>>>> +  // Emit CodeView if -Z7 or -Zd are present.
>>>>>>> +  if (Arg *DebugInfoArg =
>>>>>>> +          Args.getLastArg(options::OPT__SLASH_Z7,
>>>>>>> options::OPT__SLASH_Zd)) {
>>>>>>> +    *EmitCodeView = true;
>>>>>>> +    if (DebugInfoArg->getOption().matches(options::OPT__SLASH_Z7))
>>>>>>> +      *DebugInfoKind = codegenoptions::LimitedDebugInfo;
>>>>>>> +    else
>>>>>>> +      *DebugInfoKind = codegenoptions::DebugLineTablesOnly;
>>>>>>>      CmdArgs.push_back("-gcodeview");
>>>>>>> +  } else {
>>>>>>> +    *EmitCodeView = false;
>>>>>>> +  }
>>>>>>>
>>>>>>>    const Driver &D = getToolChain().getDriver();
>>>>>>>    EHFlags EH = parseClangCLEHFlags(D, Args);
>>>>>>> @@ -9964,7 +9970,8 @@ void visualstudio::Linker::ConstructJob(
>>>>>>>
>>>>>>>    CmdArgs.push_back("-nologo");
>>>>>>>
>>>>>>> -  if (Args.hasArg(options::OPT_g_Group, options::OPT__SLASH_Z7))
>>>>>>> +  if (Args.hasArg(options::OPT_g_Group, options::OPT__SLASH_Z7,
>>>>>>> +                  options::OPT__SLASH_Zd))
>>>>>>>      CmdArgs.push_back("-debug");
>>>>>>>
>>>>>>>    bool DLL = Args.hasArg(options::OPT__SLASH_LD,
>>>>>>> options::OPT__SLASH_LDd,
>>>>>>>
>>>>>>> Modified: cfe/trunk/test/Driver/cl-options.c
>>>>>>> URL:
>>>>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/cl-options.c?rev=274991&r1=274990&r2=274991&view=diff
>>>>>>>
>>>>>>> ==============================================================================
>>>>>>> --- cfe/trunk/test/Driver/cl-options.c (original)
>>>>>>> +++ cfe/trunk/test/Driver/cl-options.c Sat Jul  9 16:49:16 2016
>>>>>>> @@ -420,7 +420,7 @@
>>>>>>>  // Z7: "-gcodeview"
>>>>>>>  // Z7: "-debug-info-kind=limited"
>>>>>>>
>>>>>>> -// RUN: %clang_cl -gline-tables-only /Z7 /c -### -- %s 2>&1 |
>>>>>>> FileCheck -check-prefix=Z7GMLT %s
>>>>>>> +// RUN: %clang_cl /Zd /c -### -- %s 2>&1 | FileCheck
>>>>>>> -check-prefix=Z7GMLT %s
>>>>>>>  // Z7GMLT: "-gcodeview"
>>>>>>>  // Z7GMLT: "-debug-info-kind=line-tables-only"
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> cfe-commits mailing list
>>>>>>> cfe-commits at lists.llvm.org
>>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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