[llvm] r234343 - Enable W4 warnings by default for MSVC builds

[Zachary Turner]

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

On Mon, Apr 13, 2015 at 11:55 AM Kaylor, Andrew <andrew.kaylor at intel.com>
wrote:

> I'm not sure I understand.  Are you saying this problem only happens if
> you have CMAKE_CXX_FLAGS defined to include W3?
>
> 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.
>
> 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.
>
> -Andy
>
> -----Original Message-----
> From: aaron.ballman at gmail.com [mailto:aaron.ballman at gmail.com] On Behalf
> Of Aaron Ballman
> Sent: Monday, April 13, 2015 11:44 AM
> To: Zachary Turner
> Cc: Kaylor, Andrew; llvm-commits at cs.uiuc.edu
> Subject: Re: [llvm] r234343 - Enable W4 warnings by default for MSVC builds
>
> When I do that, the first line of output shows /W3:
>
>
> E:\llvm\x64>"D:\Program Files (x86)\Microsoft Visual Studio
> 12.0\VC\vcvarsall.bat" amd64
>
> E:\llvm\x64>cmake -G "Visual Studio 12" ..\llvm CMAKE_CXX_FLAGS =  /DWIN32
> /D_WINDOWS /W3 /GR /EHsc ....
>
> ~Aaron
>
> On Mon, Apr 13, 2015 at 2:37 PM, Zachary Turner <zturner at google.com>
> wrote:
> > Also what version of CMake are you using?  Maybe it's an issue with
> > CMake >= 3.0?  Try putting the following line at the top of your
> > CMakeLists.txt
> >
> > message("CMAKE_CXX_FLAGS = ${CMAKE_CXX_FLAGS}")
> >
> > If you don't see /W3 in there, you won't hit the problem.
> >
> > On Mon, Apr 13, 2015 at 11:36 AM Zachary Turner <zturner at google.com>
> wrote:
> >>
> >> Just realized maybe 2012 was a typo.  Are you actually still using 2012?
> >> I thought support was dropped.
> >>
> >> On Mon, Apr 13, 2015 at 11:33 AM Aaron Ballman
> >> <aaron at aaronballman.com>
> >> wrote:
> >>>
> >>> I do not get the warnings when building x64 or x86 on Windows 7,
> >>> MSVC 2012, debug build. This is when building LLVM, Clang, lld, and
> >>> clang tools extra
> >>>
> >>> ~Aaron
> >>>
> >>> On Mon, Apr 13, 2015 at 2:22 PM, Zachary Turner <zturner at google.com>
> >>> wrote:
> >>> > I'm building x64.  Can you try that?  Run "vcvarsall amd64" before
> >>> > building LLVM
> >>> >
> >>> > On Mon, Apr 13, 2015 at 11:21 AM Kaylor, Andrew
> >>> > <andrew.kaylor at intel.com>
> >>> > wrote:
> >>> >>
> >>> >> I haven’t seen that.  I’m not seeing any warnings right now.
> >>> >>
> >>> >>
> >>> >>
> >>> >> From: Zachary Turner [mailto:zturner at google.com]
> >>> >> Sent: Monday, April 13, 2015 11:17 AM
> >>> >> To: Kaylor, Andrew; llvm-commits at cs.uiuc.edu
> >>> >> Subject: Re: [llvm] r234343 - Enable W4 warnings by default for
> >>> >> MSVC builds
> >>> >>
> >>> >>
> >>> >>
> >>> >> Hi Andy, this is causing a huge slew of warning spam.  Is this
> >>> >> expected?
> >>> >> CMake passes /W3 by default, so  every single translation unit I
> >>> >> compile gives me the following warning:
> >>> >>
> >>> >>
> >>> >>
> >>> >> cl : Command line warning D9025 : overriding '/W3' with '/W4'
> >>> >>
> >>> >>
> >>> >>
> >>> >> Furthermore, since this is a command line warning and not a
> >>> >> compiler warning, it cannot be suppressed.  Unless you have any
> >>> >> better ideas on how to address this, I think this should be
> >>> >> reverted.
> >>> >>
> >>> >>
> >>> >>
> >>> >> On Tue, Apr 7, 2015 at 12:07 PM Andrew Kaylor
> >>> >> <andrew.kaylor at intel.com>
> >>> >> wrote:
> >>> >>
> >>> >> Author: akaylor
> >>> >> Date: Tue Apr  7 14:01:01 2015
> >>> >> New Revision: 234343
> >>> >>
> >>> >> URL: http://llvm.org/viewvc/llvm-project?rev=234343&view=rev
> >>> >> Log:
> >>> >> Enable W4 warnings by default for MSVC builds
> >>> >>
> >>> >> Modified:
> >>> >>     llvm/trunk/CMakeLists.txt
> >>> >>
> >>> >> Modified: llvm/trunk/CMakeLists.txt
> >>> >> URL:
> >>> >>
> >>> >> http://llvm.org/viewvc/llvm-project/llvm/trunk/CMakeLists.txt?rev
> >>> >> =234343&r1=234342&r2=234343&view=diff
> >>> >>
> >>> >>
> >>> >> =================================================================
> >>> >> =============
> >>> >> --- llvm/trunk/CMakeLists.txt (original)
> >>> >> +++ llvm/trunk/CMakeLists.txt Tue Apr  7 14:01:01 2015
> >>> >> @@ -233,14 +233,7 @@ list(REMOVE_DUPLICATES LLVM_TARGETS_TO_B
> >>> >>  include(AddLLVMDefinitions)
> >>> >>
> >>> >>  option(LLVM_ENABLE_PIC "Build Position-Independent Code" ON)
> >>> >> -
> >>> >> -# MSVC has a gazillion warnings with this.
> >>> >> -if( MSVC )
> >>> >> -  option(LLVM_ENABLE_WARNINGS "Enable compiler warnings." OFF)
> >>> >> -else()
> >>> >> -  option(LLVM_ENABLE_WARNINGS "Enable compiler warnings." ON)
> >>> >> -endif()
> >>> >> -
> >>> >> +option(LLVM_ENABLE_WARNINGS "Enable compiler warnings." ON)
> >>> >>  option(LLVM_ENABLE_MODULES "Compile with C++ modules enabled."
> >>> >> OFF)  option(LLVM_ENABLE_CXX1Y "Compile with C++1y enabled." OFF)
> >>> >> option(LLVM_ENABLE_LIBCXX "Use libc++ if available." OFF)
> >>> >>
> >>> >>
> >>> >> _______________________________________________
> >>> >> llvm-commits mailing list
> >>> >> llvm-commits at cs.uiuc.edu
> >>> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> >>> >
> >>> >
> >>> > _______________________________________________
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> >>> >
>
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