[edk2-devel] [PATCH] MdePkg Base.h: Delete prototype for __builtin_return_address

[Liming Gao]

Clarke:
  Do you mean CLANG compiler may have the different prototype for __builtin_return_address()? If so, dose __builtin_return_address (L) always work? 

Thanks
Liming
> -----Original Message-----
> From: devel at edk2.groups.io <devel at edk2.groups.io> On Behalf Of Leif Lindholm
> Sent: Monday, July 20, 2020 10:05 PM
> To: Jessica Clarke <jrtc27 at jrtc27.com>
> Cc: devel at edk2.groups.io; Kinney, Michael D <michael.d.kinney at intel.com>; Gao, Liming <liming.gao at intel.com>
> Subject: Re: [edk2-devel] [PATCH] MdePkg Base.h: Delete prototype for __builtin_return_address
> 
> +Mike, Liming
> 
> On Mon, Jul 20, 2020 at 14:49:46 +0100, Jessica Clarke wrote:
> > REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1004
> >
> > Being a compiler builtin, the type of __builtin_return_address is
> > already known to the compiler so no prototype is needed. Clang also
> > errors out when redeclaring certain builtins like this[1], though
> > currently only for ones with custom type checking. At the moment,
> > __builtin_return_address does not use custom type checking and so does
> > not trigger this error, however, the CHERI fork of LLVM, which will form
> > the basis of the toolchain for Arm's experimental Morello platform, does
> > use custom type checking for it, and so gives an error. Thus, simply
> > delete the unnecessary line.
> >
> > [1] https://github.com/llvm/llvm-project/commit/41af97137572ad6d4dafc872e7ecf6bbb08d4984
> >
> > Cc: Leif Lindholm <leif at nuviainc.com>
> > Signed-off-by: Jessica Clarke <jrtc27 at jrtc27.com>
> > ---
> >  MdePkg/Include/Base.h | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/MdePkg/Include/Base.h b/MdePkg/Include/Base.h
> > index 85a091b9d5..8e4271f6ea 100644
> > --- a/MdePkg/Include/Base.h
> > +++ b/MdePkg/Include/Base.h
> > @@ -1273,7 +1273,6 @@ typedef UINTN RETURN_STATUS;
> >    **/
> >    #define RETURN_ADDRESS(L)     ((L == 0) ? _ReturnAddress() : (VOID *) 0)
> >  #elif defined (__GNUC__) || defined (__clang__)
> > -  void * __builtin_return_address (unsigned int level);
> 
> Agreed this looks somewhat bonkers.
> And I can't see any ill effects from dropping it, so:
> Reviewed-by: Leif Lindholm <leif at nuviainc.com>
> 
> >    /**
> >      Get the return address of the calling function.
> >
> > --
> > 2.20.1
> >
> 
> 


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