<div dir="ltr">Will commit the patch to strip /W3 tomorrow morning if there's no further objections.<br></div><br><div class="gmail_quote">On Mon, Apr 13, 2015 at 12:25 PM Aaron Ballman <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On Mon, Apr 13, 2015 at 3:21 PM, Zachary Turner <<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>> wrote:<br>
> I think I figured all this out (mostly). Basically it only happens with<br>
> Ninja. Ninja doesn't know what command line options actually mean, it just<br>
> makes a big list of them and passes them through for each file. The Visual<br>
> Studio generator has to know, because to make a meaningful Visual Studio<br>
> project it has to generate XML with semantic tags like<br>
> <WarningLevel>Level4</WarningLevel>. So I think what happens is the Visual<br>
> Studio generator seems /W3 then later sees /W4 and only generates one tag in<br>
> the vcxproj (I confirmed that even in my case where /W3 and /W4 are part of<br>
> CMAKE_CXX_FLAGS, Only a single <WarningLevel>Level4</WarningLevel> goes into<br>
> the vcxproj.<br>
><br>
> There's still the question of why your CMAKE_CXX_FLAGS doesn't contain<br>
> anything, and I'm not sure about that. But I don't think it matters much,<br>
> because you would be seeing the same behavior with Visual Studio either way<br>
> (namely, that it would work).<br>
><br>
> On the other hand, ninja just appends commands line and passes them all<br>
> through without knowing what they mean, so it can't be made smart enough to<br>
> know that /W3 and /W4 should be collapsed. You can verify that running "cl<br>
> /W3 /W4 foo.cpp" will reproduce the error, for example.<br>
><br>
> The patch I included earlier removes /W3 from the command line, but only if<br>
> it's about to append /W4. I think this should cover everything? Aaron<br>
> raised a question on IRC about what happens if the user manually specifies a<br>
> warning level on the command line. I don't have a good answer to that,<br>
> other than to say that if you manually write CMAKE_CXX_FLAGS:STRING="/W2" or<br>
> something at CMake time, the current patch is already messed up as it will<br>
> then append /W4 which in the best could would overwrite your /W2 setting,<br>
> and in the worst case would give the warnings I'm seeing here. So I feel<br>
> like we should just be able to ignore this case, and if it becomes an issue<br>
> for someone in the future, we can add something like -DMSVC_WARNING_LEVEL<br>
> which will allow us a better means to be able to override the /W4 with<br>
> something else.<br>
<br>
If we're not regressing behavior with the patch you posted, then I<br>
think that patch is good. We definitely don't want a ton of warnings<br>
with Ninja.<br>
<br>
~Aaron<br>
<br>
><br>
> On Mon, Apr 13, 2015 at 12:11 PM Kaylor, Andrew <<a href="mailto:andrew.kaylor@intel.com" target="_blank">andrew.kaylor@intel.com</a>><br>
> wrote:<br>
>><br>
>> I’m not set up for Ninja, so I get this:<br>
>><br>
>><br>
>><br>
>> CMake Error: CMake was unable to find a build program corresponding to<br>
>> "Ninja".<br>
>><br>
>><br>
>><br>
>><br>
>><br>
>> But really I don’t know how much time it’s worth spending to figure out<br>
>> why it isn’t happening to me. It is happening to you so we need to fix it.<br>
>><br>
>><br>
>><br>
>><br>
>><br>
>> From: Zachary Turner [mailto:<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>]<br>
>> Sent: Monday, April 13, 2015 12:02 PM<br>
>><br>
>><br>
>> To: Kaylor, Andrew; Aaron Ballman<br>
>> Cc: <a href="mailto:llvm-commits@cs.uiuc.edu" target="_blank">llvm-commits@cs.uiuc.edu</a><br>
>> Subject: Re: [llvm] r234343 - Enable W4 warnings by default for MSVC<br>
>> builds<br>
>><br>
>><br>
>><br>
>> Can you try the ninja generator? First run "vcvarsall amd64", then just<br>
>> run "cmake -G Ninja f:\users\akaylor\llvm-s\llvm". That's the only<br>
>> difference I can see in what we're doing.<br>
>><br>
>><br>
>><br>
>> On Mon, Apr 13, 2015 at 12:00 PM Kaylor, Andrew <<a href="mailto:andrew.kaylor@intel.com" target="_blank">andrew.kaylor@intel.com</a>><br>
>> wrote:<br>
>><br>
>> I added the line you suggested to CMakeLists.txt, and this is what I see:<br>
>><br>
>><br>
>><br>
>> f:\users\akaylor\llvm-s\test>cmake -G "Visual Studio 12 2013 Win64"<br>
>> f:\users\akaylor\llvm-s\llvm<br>
>><br>
>> CMAKE_CXX_FLAGS =<br>
>><br>
>> -- No build type selected, default to Debug<br>
>><br>
>> -- The C compiler identification is MSVC 18.0.31101.0<br>
>><br>
>> …<br>
>><br>
>><br>
>><br>
>> Also, the /W3 flag isn’t being used during my build.<br>
>><br>
>><br>
>><br>
>> -Andy<br>
>><br>
>><br>
>><br>
>><br>
>><br>
>> From: Zachary Turner [mailto:<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>]<br>
>> Sent: Monday, April 13, 2015 11:57 AM<br>
>> To: Kaylor, Andrew; Aaron Ballman<br>
>> Cc: <a href="mailto:llvm-commits@cs.uiuc.edu" target="_blank">llvm-commits@cs.uiuc.edu</a><br>
>><br>
>><br>
>> Subject: Re: [llvm] r234343 - Enable W4 warnings by default for MSVC<br>
>> builds<br>
>><br>
>><br>
>><br>
>> No, CMake itself initializes CMAKE_CXX_FLAGS to include /W3. By default,<br>
>> if you do nothing, CMAKE_CXX_FLAGS will have /W3. You can verify this by<br>
>> printing the value of CMAKE_CXX_FLAGS in the first line of<br>
>> llvm/CMakeLists.txt<br>
>><br>
>><br>
>><br>
>> On Mon, Apr 13, 2015 at 11:55 AM Kaylor, Andrew <<a href="mailto:andrew.kaylor@intel.com" target="_blank">andrew.kaylor@intel.com</a>><br>
>> wrote:<br>
>><br>
>> I'm not sure I understand. Are you saying this problem only happens if<br>
>> you have CMAKE_CXX_FLAGS defined to include W3?<br>
>><br>
>> I don't have CMAKE_CXX_FLAGS defined on my system and my version of CMake<br>
>> (3.0.1) isn't defining it on its own, which would explain why I'm not seeing<br>
>> the problem. I guess your patch to strip W3 if it's there is OK, though it<br>
>> should probably also look for W1 and W2.<br>
>><br>
>> On the other hand, if there isn't some non-user reason that W3 would be<br>
>> part of CMAKE_CXX_FLAGS I would say this fall under the "don't do that"<br>
>> category of fix.<br>
>><br>
>> -Andy<br>
>><br>
>> -----Original Message-----<br>
>> From: <a href="mailto:aaron.ballman@gmail.com" target="_blank">aaron.ballman@gmail.com</a> [mailto:<a href="mailto:aaron.ballman@gmail.com" target="_blank">aaron.ballman@gmail.com</a>] On Behalf<br>
>> Of Aaron Ballman<br>
>> Sent: Monday, April 13, 2015 11:44 AM<br>
>> To: Zachary Turner<br>
>> Cc: Kaylor, Andrew; <a href="mailto:llvm-commits@cs.uiuc.edu" target="_blank">llvm-commits@cs.uiuc.edu</a><br>
>> Subject: Re: [llvm] r234343 - Enable W4 warnings by default for MSVC<br>
>> builds<br>
>><br>
>> When I do that, the first line of output shows /W3:<br>
>><br>
>><br>
>> E:\llvm\x64>"D:\Program Files (x86)\Microsoft Visual Studio<br>
>> 12.0\VC\vcvarsall.bat" amd64<br>
>><br>
>> E:\llvm\x64>cmake -G "Visual Studio 12" ..\llvm CMAKE_CXX_FLAGS = /DWIN32<br>
>> /D_WINDOWS /W3 /GR /EHsc ....<br>
>><br>
>> ~Aaron<br>
>><br>
>> On Mon, Apr 13, 2015 at 2:37 PM, Zachary Turner <<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>><br>
>> wrote:<br>
>> > Also what version of CMake are you using? Maybe it's an issue with<br>
>> > CMake >= 3.0? Try putting the following line at the top of your<br>
>> > CMakeLists.txt<br>
>> ><br>
>> > message("CMAKE_CXX_FLAGS = ${CMAKE_CXX_FLAGS}")<br>
>> ><br>
>> > If you don't see /W3 in there, you won't hit the problem.<br>
>> ><br>
>> > On Mon, Apr 13, 2015 at 11:36 AM Zachary Turner <<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>><br>
>> > wrote:<br>
>> >><br>
>> >> Just realized maybe 2012 was a typo. Are you actually still using<br>
>> >> 2012?<br>
>> >> I thought support was dropped.<br>
>> >><br>
>> >> On Mon, Apr 13, 2015 at 11:33 AM Aaron Ballman<br>
>> >> <<a href="mailto:aaron@aaronballman.com" target="_blank">aaron@aaronballman.com</a>><br>
>> >> wrote:<br>
>> >>><br>
>> >>> I do not get the warnings when building x64 or x86 on Windows 7,<br>
>> >>> MSVC 2012, debug build. This is when building LLVM, Clang, lld, and<br>
>> >>> clang tools extra<br>
>> >>><br>
>> >>> ~Aaron<br>
>> >>><br>
>> >>> On Mon, Apr 13, 2015 at 2:22 PM, Zachary Turner <<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>><br>
>> >>> wrote:<br>
>> >>> > I'm building x64. Can you try that? Run "vcvarsall amd64" before<br>
>> >>> > building LLVM<br>
>> >>> ><br>
>> >>> > On Mon, Apr 13, 2015 at 11:21 AM Kaylor, Andrew<br>
>> >>> > <<a href="mailto:andrew.kaylor@intel.com" target="_blank">andrew.kaylor@intel.com</a>><br>
>> >>> > wrote:<br>
>> >>> >><br>
>> >>> >> I haven’t seen that. I’m not seeing any warnings right now.<br>
>> >>> >><br>
>> >>> >><br>
>> >>> >><br>
>> >>> >> From: Zachary Turner [mailto:<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>]<br>
>> >>> >> Sent: Monday, April 13, 2015 11:17 AM<br>
>> >>> >> To: Kaylor, Andrew; <a href="mailto:llvm-commits@cs.uiuc.edu" target="_blank">llvm-commits@cs.uiuc.edu</a><br>
>> >>> >> Subject: Re: [llvm] r234343 - Enable W4 warnings by default for<br>
>> >>> >> MSVC builds<br>
>> >>> >><br>
>> >>> >><br>
>> >>> >><br>
>> >>> >> Hi Andy, this is causing a huge slew of warning spam. Is this<br>
>> >>> >> expected?<br>
>> >>> >> CMake passes /W3 by default, so every single translation unit I<br>
>> >>> >> compile gives me the following warning:<br>
>> >>> >><br>
>> >>> >><br>
>> >>> >><br>
>> >>> >> cl : Command line warning D9025 : overriding '/W3' with '/W4'<br>
>> >>> >><br>
>> >>> >><br>
>> >>> >><br>
>> >>> >> Furthermore, since this is a command line warning and not a<br>
>> >>> >> compiler warning, it cannot be suppressed. Unless you have any<br>
>> >>> >> better ideas on how to address this, I think this should be<br>
>> >>> >> reverted.<br>
>> >>> >><br>
>> >>> >><br>
>> >>> >><br>
>> >>> >> On Tue, Apr 7, 2015 at 12:07 PM Andrew Kaylor<br>
>> >>> >> <<a href="mailto:andrew.kaylor@intel.com" target="_blank">andrew.kaylor@intel.com</a>><br>
>> >>> >> wrote:<br>
>> >>> >><br>
>> >>> >> Author: akaylor<br>
>> >>> >> Date: Tue Apr 7 14:01:01 2015<br>
>> >>> >> New Revision: 234343<br>
>> >>> >><br>
>> >>> >> URL: <a href="http://llvm.org/viewvc/llvm-project?rev=234343&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=234343&view=rev</a><br>
>> >>> >> Log:<br>
>> >>> >> Enable W4 warnings by default for MSVC builds<br>
>> >>> >><br>
>> >>> >> Modified:<br>
>> >>> >> llvm/trunk/CMakeLists.txt<br>
>> >>> >><br>
>> >>> >> Modified: llvm/trunk/CMakeLists.txt<br>
>> >>> >> URL:<br>
>> >>> >><br>
>> >>> >> <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/CMakeLists.txt?rev" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/CMakeLists.txt?rev</a><br>
>> >>> >> =234343&r1=234342&r2=234343&view=diff<br>
>> >>> >><br>
>> >>> >><br>
>> >>> >> =================================================================<br>
>> >>> >> =============<br>
>> >>> >> --- llvm/trunk/CMakeLists.txt (original)<br>
>> >>> >> +++ llvm/trunk/CMakeLists.txt Tue Apr 7 14:01:01 2015<br>
>> >>> >> @@ -233,14 +233,7 @@ list(REMOVE_DUPLICATES LLVM_TARGETS_TO_B<br>
>> >>> >> include(AddLLVMDefinitions)<br>
>> >>> >><br>
>> >>> >> option(LLVM_ENABLE_PIC "Build Position-Independent Code" ON)<br>
>> >>> >> -<br>
>> >>> >> -# MSVC has a gazillion warnings with this.<br>
>> >>> >> -if( MSVC )<br>
>> >>> >> - option(LLVM_ENABLE_WARNINGS "Enable compiler warnings." OFF)<br>
>> >>> >> -else()<br>
>> >>> >> - option(LLVM_ENABLE_WARNINGS "Enable compiler warnings." ON)<br>
>> >>> >> -endif()<br>
>> >>> >> -<br>
>> >>> >> +option(LLVM_ENABLE_WARNINGS "Enable compiler warnings." ON)<br>
>> >>> >> option(LLVM_ENABLE_MODULES "Compile with C++ modules enabled."<br>
>> >>> >> OFF) option(LLVM_ENABLE_CXX1Y "Compile with C++1y enabled." OFF)<br>
>> >>> >> option(LLVM_ENABLE_LIBCXX "Use libc++ if available." OFF)<br>
>> >>> >><br>
>> >>> >><br>
>> >>> >> _______________________________________________<br>
>> >>> >> llvm-commits mailing list<br>
>> >>> >> <a href="mailto:llvm-commits@cs.uiuc.edu" target="_blank">llvm-commits@cs.uiuc.edu</a><br>
>> >>> >> <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits" target="_blank">http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits</a><br>
>> >>> ><br>
>> >>> ><br>
>> >>> > _______________________________________________<br>
>> >>> > llvm-commits mailing list<br>
>> >>> > <a href="mailto:llvm-commits@cs.uiuc.edu" target="_blank">llvm-commits@cs.uiuc.edu</a><br>
>> >>> > <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits" target="_blank">http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits</a><br>
>> >>> ><br>
</blockquote></div>