Testing GDC (GCC 7.1) on Runtime-less ARM Cortex-M

[Iain Buclaw via D.gnu]

On 25 June 2017 at 13:30, Mike via D.gnu <d.gnu at puremagic.com> wrote:
> On Sunday, 25 June 2017 at 10:53:35 UTC, Mike wrote:
>
>> I'm not really interested in that because its too blunt of an instrument.
>> I'd like to use TypeInfo, but only if I'm doing dynamic casts or other
>> things that require such runtime information.  Also, I'd only want the
>> TypeInfo for the types that need it in my binary.  I've said this before but
>> I'll repeat:  I like TypeInfo; I just don't like dead code.
>
>
> Just a little more information about this.  It doesn't appear that the
> entire TypeInfo object is remaining in the binary.  It appears to only be
> the `name` of the type that the linker just can't seem to "garbage
> collection" from the .rodata section.
>
> Mike
>
>

Ah ha! It seems that for whatever reason, binutils can't strip
strings.  But if you wrap that string around a static symbol, then has
no problem removing it.

Using your small test here:  https://issues.dlang.org/show_bug.cgi?id=14758

Making the following modifications for gdc.

---
long syscall(long code, long arg1 = 0, in void* arg2 = null, long arg3 = 0)
{
    long result = void;

    asm { "syscall"
        : /* "=a" (result) ??? No output operands == asm volatile?
That seems wrong... */
        : "a" (code), "D" (arg1), "S" (arg2), "d" (arg3);
    }

    return result;
}
---

Compiling with -fdata-sections -Os shows that .rodata now only contains:

Contents of section .rodata:
 40010e 48656c6c 6f0a00                      Hello..


I'll make a formal PR when I have some time later.

Iain.