Re: [Valgrind-developers] Tracing the origin of uninitialised memory

[Nicholas N. <nj...@ca...>]

On Sun, 7 Nov 2004, Maurice van der Pot wrote:

> 1) Is it allowed to simply call VG_(synth_ccall) multiple times from
>   within synth_LOADV for instance? I was planning something like
>   this:
>
>     VG_(synth_ccall) ( helper, 1, 1, argv, tagv, tv_reg,
>                        regs_live_before, regs_live_after );
>
>     UInt argv2[] = { a_reg,   tv_reg };
>     Tag  tagv2[] = { RealReg, RealReg };
>
>     VG_(synth_ccall) ( helper2, 2, 2, argv2, tagv2, INVALID_REALREG,
>                        regs_live_after, regs_live_after );

No, as this comment says:

    WARNING:  a UInstr should *not* be translated with synth_ccall followed
    by some other x86 assembly code;  vg_liveness_analysis() doesn't expect
    such behaviour and everything will fall over.


> 2) Is there a way to get to a register itself instead of the value it
>   contains, from a helper function?  In helper2 I would like to somehow
>   modify some information about tv_reg dependent on both tv_reg's own
>   value and the value of a_reg.
>
>A 3) Alternatively i might want to add code to do this to the first helper
>   function. Is it possible to get to the register that will receive the
>   return value? Or should I modify synth_ccall to receive not only the
>   return value but also the extra information that needs to be remembered
>   about the return value register?

If it's only LOADV that you want to augment, I would add an extra arg to 
the functions that get called by LOADV, and pass in whatever extra info 
you need that way, if you see what I mean.

N