[cfe-dev] "no input files" error when specifying language?

[Justin Bogner via cfe-dev]

Rick Mann via cfe-dev <cfe-dev at lists.llvm.org> writes:
> In the ARM Linux development world, it's common to use gcc to
> pre-process "Device Tree" files to take advantage of #include and
> #define directives. Unfortunately, the DT syntax also includes the use
> of the '#', so they specify -x assembler-with-cpp, and it processes
> nicely. The typical invocation (with gcc) looks like this:
>
> cpp -Wp,-MD,src/arm/.am335x-arduino-tre.dtb.d.pre.tmp -nostdinc
> -Iinclude -Isrc/arm -Itestcase-data -undef -D__DTS__ -x
> assembler-with-cpp -o src/arm/.am335x-arduino-tre.dtb.dts.tmp
> src/arm/am335x-arduino-tre.dts
>
> A simplified invocation is:
>
> 	cpp -x assembler-with-cpp -o FILE.temp.dts FILE.dts
>
> clang doesn't like this. It's okay with this:
>
> 	cpp FILE.dts
>
> But of course it complains about the invalid preprocessing directive
> it finds (e.g. "#address-cells = <1>;"). The cure for this is "-x
> assembler-with-cpp", but if I invoke it like this:
>
> 	cpp -x assembler-with-cpp FILE.dts
>
> It says "clang: error: no input files". If I place the filename
> FILE.dts before any of the options, they don't get applied to that
> file.
>
> The clang I'm trying this with is:
>
> $ clang --version
> Apple LLVM version 7.0.0 (clang-700.0.72)
> Target: x86_64-apple-darwin14.5.0
> Thread model: posix
>
> Is there any way to do what I want to do here?

Does it work if you invoke `clang -E` instead of `cpp`? ie,

  clang -E -x assembler-with-cpp -o FILE.temp.dts FILE.dts