llvm dev - Nov 2016 - "-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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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] 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>
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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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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