[cfe-dev] Use of -Xclang and forwarding to GCC

[Amaury Pouly]

I filed a bug, see bug 7826.

Amaury Pouly


2010/8/4 Douglas Gregor <dgregor at apple.com>

>
> On Aug 4, 2010, at 4:57 PM, Amaury Pouly wrote:
>
> > Hello,
> > I ran into a problem when using the -Xclang switch. According to the
> documentation it says that it 'Pass arg to the clang compiler frontend.'.
> But then, when I use it, the arguments are also passed to the assembler and
> the linker. Example (the -W switch is a random one, I just picked it because
> clang -cc1 recognizes it):
> >
> > # clang -ccc-echo -Xclang -W -o ioi ioi.c
> > "/home/pamaury/avalon/bin/clang" -cc1 -triple x86_64-unknown-linux-gnu -S
> -disable-free -main-file-name ioi.c -mrelocation-model static
> -mdisable-fp-elim -mconstructor-aliases -munwind-tables -target-cpu x86-64
> -resource-dir /home/pamaury/avalon/lib/clang/2.8 -ferror-limit 19
> -fmessage-length 202 -fgnu-runtime -fdiagnostics-show-option
> -fcolor-diagnostics -W -o /tmp/cc-0rvFL5.s -x c ioi.c
> >  "/usr/bin/gcc" -Xclang -W -c -m64 -o /tmp/cc-GuWlIA.o -x assembler
> /tmp/cc-0rvFL5.s
> > gcc: unrecognized option '-Xclang'
> >  "/usr/bin/gcc" -Xclang -W -m64 -o ioi /tmp/cc-GuWlIA.o
> > gcc: unrecognized option '-Xclang'
> >
> > Looking at the code, it seems that this is because the generic gcc code
> in gcc::Common::ConstructJob forwards an argument if the option
> hasForwardToGCC() and hasForwardToGCC() itself is defined as:
> >
> > bool hasForwardToGCC() const { return !DriverOption && !LinkerInput; }
> >
> > Which seems strange to me because obviously, clang will not use GCC as
> the compiler itself (that would defeat the point of using clang :)) so when
> using the -Xclang option which is not a driver option nor a linker input but
> clearly a compiler related switch, it should not be forwarded to gcc.
> >
> > Am I missing something there or this really a bug ?
>
> Looks like a bug.
>
>        - Doug
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