llvm dev - May 2014 - [LLVMdev] Should this function be omitted?

Hi all,

Is there any reason why the following code produces the attached assembly
code?

    struct X { int v; };

    int func( X** x, int n )
    {
        int sum = 0;

        while ( n > 0 )
        {
            sum += (*x)->v;
            ++x;
            --n;
        }
        return sum;
    }

    int main() {}

The "func" function is not used, I think it should be omitted by the
linked. Should it?

Compiled using:
    clang++ -S -O3 -std=c++11 -S code.cpp

clang++ --version
    clang version 3.5 (trunk 200620)
    Target: x86_64-apple-darwin13.1.0
    Thread model: posix

Assembly code generated:
    http://pastebin.com/aY8rAXyQ

Best,
Fernando.
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I've replied on the cfe-dev thread for this, but basically you need to
tell the linker to dead strip out unused code. Since you're on darwin
you can pass -Wl,-dead_strip.

-eric

On Sun, May 4, 2014 at 4:17 PM, Fernando Pelliccioni
<fpelliccioni at gmail.com> wrote:
> Hi all,
>
> Is there any reason why the following code produces the attached assembly
> code?
>
>     struct X { int v; };
>
>     int func( X** x, int n )
>     {
>         int sum = 0;
>
>         while ( n > 0 )
>         {
>             sum += (*x)->v;
>             ++x;
>             --n;
>         }
>         return sum;
>     }
>
>     int main() {}
>
> The "func" function is not used, I think it should be omitted by
the linked.
> Should it?
>
> Compiled using:
>     clang++ -S -O3 -std=c++11 -S code.cpp
>
> clang++ --version
>     clang version 3.5 (trunk 200620)
>     Target: x86_64-apple-darwin13.1.0
>     Thread model: posix
>
> Assembly code generated:
>     http://pastebin.com/aY8rAXyQ
>
> Best,
> Fernando.
>
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