r346491 - [clang-cl] Add warning for /Zc:dllexportInlines- when the flag is used with /fallback

Mon Nov 12 01:58:16 PST 2018

Hmm, maybe I misunderstood your initial request for this.

The current implementation does what the warnings says: If the
compiler falls back to cl.exe, /Zc:dllexportInlines- will be ignored.
This suggests to the user that it's a bad idea, but they can go ahead
if they want to.

It sounds like you're suggesting we should always ignore
/Zc:dllexportInlines- when used together with the /fallback flag? I'm
not sure that's necessarily better.. it depends on why they're using
/fallback I guess. If it's because the user has one file that clang-cl
can't handle for some reason, but they still want
/Zc:dllexportInlines- for the rest, then ignoring it would break that.

In general, I'm not sure how widely used /fallback is anymore. I
wonder if it would be possible to remove it...

On Fri, Nov 9, 2018 at 9:52 PM, Nico Weber <thakis at chromium.org> wrote:
> Ah cool. But the diagnostic is "option /dllexportInlines- is ignored when
> /fallback happens" – shouldn't it be ignored regardless of if fallback
> happens? Does that happen and the warning text is wrong?
>
> On Fri, Nov 9, 2018 at 11:20 AM Hans Wennborg <hans at chromium.org> wrote:
>>
>> On Fri, Nov 9, 2018 at 4:53 PM, Nico Weber <thakis at chromium.org> wrote:
>> > This only prints the warning when /fallback actually happens, right?
>>
>> No, it prints it when the fallback job is created, not when (or if) it
>> runs. I.e. it prints if the /fallback flag is used, regardless of
>> whether it actually falls back or not. This is reflected by the test
>> which uses -###, i.e. nothing is getting run.
>>
>> So I think we're good :-)
>>
>> > I don't
>> > think that's good enough: If we build a few TUs with /dllexportInlines-
>> > and
>> > don't fall back, those .obj files are not abi compatible with the
>> > cl-built
>> > ones. (Consider all dllexport TUs of a header being built with clang-cl
>> > but
>> > all dllimport versions of the same header being built by cl – I think
>> > this
>> > will cause link errors). SO I think we should error out if
>> > /dllexportIlnlines- /fallback is on the same line, even if the fallback
>> > doesn't actually happen.
>> >
>> > On Fri, Nov 9, 2018 at 8:28 AM Takuto Ikuta via cfe-commits
>> > <cfe-commits at lists.llvm.org> wrote:
>> >>
>> >> Author: tikuta
>> >> Date: Fri Nov  9 05:25:45 2018
>> >> New Revision: 346491
>> >>
>> >> URL: http://llvm.org/viewvc/llvm-project?rev=346491&view=rev
>> >> Log:
>> >> [clang-cl] Add warning for /Zc:dllexportInlines- when the flag is used
>> >> with /fallback
>> >>
>> >> Summary:
>> >> This is followup of
>> >> https://reviews.llvm.org/D51340
>> >>
>> >> Reviewers: hans, thakis
>> >>
>> >> Reviewed By: hans
>> >>
>> >> Subscribers: cfe-commits, llvm-commits
>> >>
>> >> Differential Revision: https://reviews.llvm.org/D54298
>> >>
>> >> Modified:
>> >>     cfe/trunk/include/clang/Basic/DiagnosticDriverKinds.td
>> >>     cfe/trunk/lib/Driver/ToolChains/MSVC.cpp
>> >>     cfe/trunk/test/Driver/cl-options.c
>> >>
>> >> Modified: cfe/trunk/include/clang/Basic/DiagnosticDriverKinds.td
>> >> URL:
>> >>
>> >> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticDriverKinds.td?rev=346491&r1=346490&r2=346491&view=diff
>> >>
>> >>
>> >> ==============================================================================
>> >> --- cfe/trunk/include/clang/Basic/DiagnosticDriverKinds.td (original)
>> >> +++ cfe/trunk/include/clang/Basic/DiagnosticDriverKinds.td Fri Nov  9
>> >> 05:25:45 2018
>> >> @@ -161,6 +161,10 @@ def warn_drv_yc_multiple_inputs_clang_cl
>> >>    "support for '/Yc' with more than one source file not implemented
>> >> yet;
>> >> flag ignored">,
>> >>    InGroup<ClangClPch>;
>> >>
>> >> +def warn_drv_non_fallback_argument_clang_cl : Warning<
>> >> +  "option '%0' is ignored when /fallback happens">,
>> >> +  InGroup<OptionIgnored>;
>> >> +
>> >>  def err_drv_invalid_value : Error<"invalid value '%1' in '%0'">;
>> >>  def err_drv_invalid_int_value : Error<"invalid integral value '%1' in
>> >> '%0'">;
>> >>  def err_drv_invalid_remap_file : Error<
>> >>
>> >> Modified: cfe/trunk/lib/Driver/ToolChains/MSVC.cpp
>> >> URL:
>> >>
>> >> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/ToolChains/MSVC.cpp?rev=346491&r1=346490&r2=346491&view=diff
>> >>
>> >>
>> >> ==============================================================================
>> >> --- cfe/trunk/lib/Driver/ToolChains/MSVC.cpp (original)
>> >> +++ cfe/trunk/lib/Driver/ToolChains/MSVC.cpp Fri Nov  9 05:25:45 2018
>> >> @@ -669,6 +669,12 @@ std::unique_ptr<Command> visualstudio::C
>> >>    // them too.
>> >>    Args.AddAllArgs(CmdArgs, options::OPT_UNKNOWN);
>> >>
>> >> +  // Warning for ignored flag.
>> >> +  if (const Arg *dllexportInlines =
>> >> +      Args.getLastArg(options::OPT__SLASH_Zc_dllexportInlines_))
>> >> +
>> >>
>> >> C.getDriver().Diag(clang::diag::warn_drv_non_fallback_argument_clang_cl)
>> >> +      << dllexportInlines->getAsString(Args);
>> >> +
>> >>    // Input filename.
>> >>    assert(Inputs.size() == 1);
>> >>    const InputInfo &II = Inputs[0];
>> >>
>> >> Modified: cfe/trunk/test/Driver/cl-options.c
>> >> URL:
>> >>
>> >> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/cl-options.c?rev=346491&r1=346490&r2=346491&view=diff
>> >>
>> >>
>> >> ==============================================================================
>> >> --- cfe/trunk/test/Driver/cl-options.c (original)
>> >> +++ cfe/trunk/test/Driver/cl-options.c Fri Nov  9 05:25:45 2018
>> >> @@ -494,6 +494,8 @@
>> >>  // NoDllExportInlines: "-fno-dllexport-inlines"
>> >>  // RUN: %clang_cl /Zc:dllexportInlines /c -### -- %s 2>&1 | FileCheck
>> >> -check-prefix=DllExportInlines %s
>> >>  // DllExportInlines-NOT: "-fno-dllexport-inlines"
>> >> +// RUN: %clang_cl /fallback /Zc:dllexportInlines- /c -### -- %s 2>&1 |
>> >> FileCheck -check-prefix=DllExportInlinesFallback %s
>> >> +// DllExportInlinesFallback: warning: option '/Zc:dllexportInlines-'
>> >> is
>> >> ignored when /fallback happens [-Woption-ignored]
>> >>
>> >>  // RUN: %clang_cl /Zi /c -### -- %s 2>&1 | FileCheck -check-prefix=Zi
>> >> %s
>> >>  // Zi: "-gcodeview"
>> >>
>> >>
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