steveire added inline comments.
================
Comment at: lib/Frontend/CompilerInvocation.cpp:792
Opts.MainFileName = Args.getLastArgValue(OPT_main_file_name);
+ if (Args.hasArg(OPT_echo_main_file_name))
+ llvm::outs() << Opts.MainFileName << "\n";
----------------
zturner wrote:
> zturner wrote:
> > steveire wrote:
> > > hans wrote:
> > > > zturner wrote:
> > > > > steveire wrote:
> > > > > > I'll have to keep a patch around anyway for myself locally to
> > > > > > remove this condition. But maybe someone else will benefit from
> > > > > > this.
> > > > > >
> > > > > > What do you think about changing CMake to so that this is passed by
> > > > > > default when using Clang-CL?
> > > > > >
> > > > > Do you mean llvms cmake? Or cmake itself? Which generator are you
> > > > > using?
> > > > Can't you just configure your build to pass the flag to clang-cl?
> > > >
> > > > I suppose CMake could be made to do that by default when using clang-cl
> > > > versions that support the flag and using the MSBuild generator, but
> > > > that's for the CMake community to decide I think. Or perhaps our VS
> > > > integration could do that, but it gets tricky because it needs to know
> > > > whether the flag is supported or not.
> > > I mean upstream cmake. My suggestion is independent of the generator, but
> > > it would depend on what Brad decides anyway. I don't intend to implement
> > > it, just report it.
> > >
> > > I only have one clang but I have multiple buildsystems, and I don't want
> > > to have to add a new flag too all of them. In each toplevel CMakeLists
> > > everyone will need this to make use of the flag:
> > >
> > > ```
> > >
> > > # Have to remember to use "${CMAKE_CXX_SIMULATE_ID}" instead of
> > > # Undecorated "CMAKE_CXX_SIMULATE_ID" because there is a
> > > # variable named "MSVC" and
> > > # the way CMake variables and the "if()" command work requires this.
> > > if (CMAKE_CXX_COMPILER_ID STREQUAL Clang
> > > AND ${CMAKE_CXX_SIMULATE_ID} STREQUAL MSVC)
> > > # CMake does not have explicit Clang-CL support yet.
> > > # It should have a COMPILER_ID for it.
> > > set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /showFilename")
> > > # etc
> > > endif()
> > > ```
> > >
> > > Upstream CMake can have the logic to add the flag instead.
> > But then what if you don’t want it? There would be no way to turn it off.
> > I don’t think it’s a good fit for cmake
> Yes, and actually for this reason i was wondering if we can do it without a
> flag at all. What if we just set an magic environment variable? It handles
> Stephen’s use case (he can just set it globally), and MSBuild (we can set it
> in the extension).
> But then what if you don’t want it? There would be no way to turn it off.
Oh, I thought that the last flag would dominate. ie, if cmake generated
`/showFilename` and the user adds `/showFilename-`, then you would end up with
`clang-cl.exe /showFilename /showFilename-`
and it would not be shown. I guess that's not how it works.
Maybe users want to not show it, but not seeing the filename is a surprising
first-time experience when porting from MSVC to clang-cl using Visual Studio.
However, I'll just drop out of the discussion and not make any bug to CMake. If
anyone else feels strongly, they can do so.
Thanks!
https://reviews.llvm.org/D52773
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