RISC-V problem with weak function references and -mcmodel=medany

[Jim Wilson]

On 05/29/2018 04:19 AM, Sebastian Huber wrote:
> Changing the code to something like this
> 
> void f(void) __attribute__((__weak__));
> 
> void _start(void)
> {
>  Â Â Â Â Â Â Â  void (*g)(void) = f;
> 
>  Â Â Â Â Â Â Â  if (g != 0) {
>  Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  (*g)();
>  Â Â Â Â Â Â Â  }
> }

This testcase works for me also, using -mcmodel=medany -O tmp.c 
-Ttext=0x80000000 -nostdlib -nostartfiles.

I need enough info to reproduce your problem in order to look at it.

One thing you can try is adding -Wl,--noinhibit-exec, which will produce 
an executable even though there was a linker error, and then you can 
disassemble the binary to see what you have for the weak call.  That 
might give a clue as to what is wrong.

> Why doesn't the RISC-V generate a trampoline code to call far functions?

RISC-V is a new target.  The answer to questions like this is that we 
haven't needed it yet, and hence haven't implemented it yet.  But I 
don't see any need for trampolines to support a call to 0.  We can reach 
anywhere in the low 32-bit address space with auipc/jalr.  We can also 
use zero-relative addressing via the x0 register if necessary.  We 
already have some linker relaxation support for that, but it doesn't 
seem to be triggering for this testcase.

Jim