[llvm-dev] Miscellaneous warnings in code using Visual Studio

[David Blaikie via llvm-dev]

If they prove to be good cleanup/improvements to the code in general - but
we don't try too hard to be -Werror clean on every compiler, mostly just
self-hosted clang. The line is fuzzy - if a warning isn't /too/ bad (ie:
doesn't require extreme contortions to the code to address the warning)
then fixing instances seems ok. If it's unhelpful (eg: a warning has a high
false positive rate and/or clang's equivalent warning is more nuanced and
avoids the need to touch false positives) we may disable warnings in LLVM.
(this doesn't address the issue of warnings in LLVM's public headers - not
every downstream consumer of LLVM is going to disable the same set of
warnings, so sometimes it's necessary to do some warning cleanup even for
undesirable warnings)

On Tue, Jan 12, 2021 at 9:14 AM Paul C. Anagnostopoulos via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> When I build on Windows 7 with Visual Studio, I get various warnings that
> were ignored until I recently set
>
> LLVM_ENABLE_WERROR:BOOL=ON
>
> One example is shown below. Should I take the time to hunt these down and
> fix them?
>
>
> **********************************************************************
> ** Visual Studio 2019 Developer Command Prompt v16.8.1
> ** Copyright (c) 2020 Microsoft Corporation
> **********************************************************************
>
> D:\LLVM\build>build-targets.bat
>         1 file(s) copied.
> [363/1578] Building CXX object
> lib\CodeGen\...LLVMGlobalISel.dir\MachineIRBuilder.cpp.obj
> FAILED:
> lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/MachineIRBuilder.cpp.obj
> C:\PROGRA~2\MIB055~1\2019\COMMUN~1\VC\Tools\MSVC\1428~1.293\bin\Hostx86\x86\cl.exe
> /nolog
> o /TP -DGTEST_HAS_RTTI=0 -DUNICODE -D_CRT_NONSTDC_NO_DEPRECATE
> -D_CRT_NONSTDC_NO_WARNINGS
> -D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS
> -D_FILE_OFFSET_BITS=64 -D_HAS_EXCEPTI
> ONS=0 -D_LARGEFILE_SOURCE -D_SCL_SECURE_NO_DEPRECATE
> -D_SCL_SECURE_NO_WARNINGS -D_UNICODE
> -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS
> -Ilib\CodeGen\Global
> ISel -IC:\LLVM\llvm-project\llvm\lib\CodeGen\GlobalISel -Iinclude
> -IC:\LLVM\llvm-project\l
> lvm\include /DWIN32 /D_WINDOWS   /WX /Zc:inline /Zc:__cplusplus
> /Zc:strictStrings /Oi /Zc:
> rvalueCast /bigobj /W4 -wd4141 -wd4146 -wd4244 -wd4267 -wd4291 -wd4351
> -wd4456 -wd4457 -wd
> 4458 -wd4459 -wd4503 -wd4624 -wd4722 -wd4100 -wd4127 -wd4512 -wd4505
> -wd4610 -wd4510 -wd47
> 02 -wd4245 -wd4706 -wd4310 -wd4701 -wd4703 -wd4389 -wd4611 -wd4805 -wd4204
> -wd4577 -wd4091
>  -wd4592 -wd4319 -wd4709 -wd4324 -w14062 -we4238 /MDd /Zi /Ob0 /Od /RTC1
> /EHs-c- /GR- -st
> d:c++14 /showIncludes
> /Folib\CodeGen\GlobalISel\CMakeFiles\LLVMGlobalISel.dir\MachineIRBui
> lder.cpp.obj
> /Fdlib\CodeGen\GlobalISel\CMakeFiles\LLVMGlobalISel.dir\LLVMGlobalISel.pdb
> /F
> S -c C:\LLVM\llvm-project\llvm\lib\CodeGen\GlobalISel\MachineIRBuilder.cpp
> C:\LLVM\llvm-project\llvm\lib\CodeGen\GlobalISel\MachineIRBuilder.cpp(657):
> error C2220: t
> he following warning is treated as an error
> C:\LLVM\llvm-project\llvm\lib\CodeGen\GlobalISel\MachineIRBuilder.cpp(657):
> warning C4018:
>  '>=': signed/unsigned mismatch
> [366/1578] Building CXX object
> lib\CodeGen\...CMakeFiles\LLVMGlobalISel.dir\Utils.cpp.obj
> ninja: build stopped: subcommand failed.
>
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