[llvm-dev] "-stdlib=libc++" applied to CMAKE_CXX_FLAGS

[Jordan Rose via llvm-dev]

Doesn't this control search paths as well? It's only because you're specifying -nostdinc++ that it's going unused for you.

Jordan


> On Nov 18, 2016, at 10:50, Brian Cain <bcain at codeaurora.org> wrote:
> 
> Jordan,
>  
> Waaay back in 2014 you added “append_if(CXX_SUPPORTS_STDLIB "-stdlib=libc++" CMAKE_CXX_FLAGS)” to HandleLLVMStdlib.cmake and I’m asking if it might’ve been in error.  I’ll submit a review to delete the CMAKE_CXX_FLAGS unless you think it still makes sense.
>  
> -Brian
>  
>  
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org <mailto:llvm-dev-bounces at lists.llvm.org>] On Behalf Of Brian Cain via llvm-dev
> Sent: Thursday, November 17, 2016 5:10 PM
> To: 'llvm-dev' <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>>
> Subject: [llvm-dev] "-stdlib=libc++" applied to CMAKE_CXX_FLAGS
>  
> llvm/cmake/modules/HandleLLVMStdlib.cmake specifies “-stdlib=libc++” for CMAKE_CXX_FLAGS when LLVM_ENABLE_LIBCXX and CXX_SUPPORTS_STDLIB.  From what I can see this is a flag intended for the linker and not the compiler.
>  
> I’d like to submit a change to delete CMAKE_CXX_FLAGS from this append() but I wanted to check in with the list to see if that makes sense or if there are other contexts for which “stdlib=libc++” might be used.
>  
> If I specify “-nostdinc++”, “-stdlib=libc++” doesn’t get consumed and clang emits a warning. 
>  
> $ clang++ -nostdinc++ -stdlib=libc++ -o main.o -c main.cpp
> clang-4.0: warning: argument unused during compilation: '-stdlib=libc++' [-Wunused-command-line-argument]

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