<div dir="ltr">I think I figured all this out (mostly). Basically it only happens with Ninja. Ninja doesn't know what command line options actually mean, it just makes a big list of them and passes them through for each file. The Visual Studio generator has to know, because to make a meaningful Visual Studio project it has to generate XML with semantic tags like <WarningLevel>Level4</WarningLevel>. So I think what happens is the Visual Studio generator seems /W3 then later sees /W4 and only generates one tag in the vcxproj (I confirmed that even in my case where /W3 and /W4 are part of CMAKE_CXX_FLAGS, Only a single <WarningLevel>Level4</WarningLevel> goes into the vcxproj.<br><div><br></div><div>There's still the question of why your CMAKE_CXX_FLAGS doesn't contain anything, and I'm not sure about that. But I don't think it matters much, because you would be seeing the same behavior with Visual Studio either way (namely, that it would work).</div><div><br></div><div>On the other hand, ninja just appends commands line and passes them all through without knowing what they mean, so it can't be made smart enough to know that /W3 and /W4 should be collapsed. You can verify that running "cl /W3 /W4 foo.cpp" will reproduce the error, for example.</div><div><br></div><div>The patch I included earlier removes /W3 from the command line, but only if it's about to append /W4. I think this should cover everything? Aaron raised a question on IRC about what happens if the user manually specifies a warning level on the command line. <span style="line-height:1.5;font-size:13.1999998092651px">I don't have a good answer to that, other than to say that if you manually write CMAKE_CXX_FLAGS:STRING="/W2" or something at CMake time, the current patch is already messed up as it will then append /W4 which in the best could would overwrite your /W2 setting, and in the worst case would give the warnings I'm seeing here. So I feel like we should just be able to ignore this case, and if it becomes an issue for someone in the future, we can add something like -DMSVC_WARNING_LEVEL which will allow us a better means to be able to override the /W4 with something else.</span></div></div><br><div class="gmail_quote">On Mon, Apr 13, 2015 at 12:11 PM Kaylor, Andrew <<a href="mailto:andrew.kaylor@intel.com">andrew.kaylor@intel.com</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">I’m not set up for Ninja, so I get this:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">CMake Error: CMake was unable to find a build program corresponding to "Ninja".<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">But really I don’t know how much time it’s worth spending to figure out why it isn’t happening to me. It is happening to you so we need to fix it.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Zachary Turner [mailto:<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>]
<br>
<b>Sent:</b> Monday, April 13, 2015 12:02 PM</span></p></div></div><div lang="EN-US" link="blue" vlink="purple"><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""><br>
<b>To:</b> Kaylor, Andrew; Aaron Ballman<br>
<b>Cc:</b> <a href="mailto:llvm-commits@cs.uiuc.edu" target="_blank">llvm-commits@cs.uiuc.edu</a><br>
<b>Subject:</b> Re: [llvm] r234343 - Enable W4 warnings by default for MSVC builds<u></u><u></u></span></p></div></div><div lang="EN-US" link="blue" vlink="purple"><div>
<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Can you try the ninja generator? First run "vcvarsall amd64", then just run "cmake -G Ninja f:\users\akaylor\llvm-s\llvm". That's the only difference I can see in what we're doing.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">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>> wrote:<u></u><u></u></p>
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<div>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">I added the line you suggested to CMakeLists.txt, and this is what I see:</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">f:\users\akaylor\llvm-s\test>cmake -G "Visual Studio 12 2013 Win64" f:\users\akaylor\llvm-s\llvm</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">CMAKE_CXX_FLAGS =</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">-- No build type selected, default to Debug</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">-- The C compiler identification is MSVC 18.0.31101.0</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">…</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Also, the /W3 flag isn’t being used during my build.</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">-Andy</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><u></u><u></u></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Zachary Turner [mailto:<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>]
<br>
<b>Sent:</b> Monday, April 13, 2015 11:57 AM<br>
<b>To:</b> Kaylor, Andrew; Aaron Ballman<br>
<b>Cc:</b> <a href="mailto:llvm-commits@cs.uiuc.edu" target="_blank">llvm-commits@cs.uiuc.edu</a></span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""><br>
<b>Subject:</b> Re: [llvm] r234343 - Enable W4 warnings by default for MSVC builds</span><u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal">No, CMake itself initializes CMAKE_CXX_FLAGS to include /W3. By default, if you do nothing, CMAKE_CXX_FLAGS will have /W3. You can verify this by printing the value of CMAKE_CXX_FLAGS
in the first line of llvm/CMakeLists.txt<u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal">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>> wrote:<u></u><u></u></p>
<p class="MsoNormal">I'm not sure I understand. Are you saying this problem only happens if 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 (3.0.1) isn't defining it on its own, which would explain why I'm not seeing the problem. I guess your patch to strip W3 if it's there is OK, though it 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 part of CMAKE_CXX_FLAGS I would say this fall under the "don't do that" 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 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 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 12.0\VC\vcvarsall.bat" amd64<br>
<br>
E:\llvm\x64>cmake -G "Visual Studio 12" ..\llvm CMAKE_CXX_FLAGS = /DWIN32 /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>> 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>> wrote:<br>
>><br>
>> Just realized maybe 2012 was a typo. Are you actually still using 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>
>>> ><u></u><u></u></p>
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