Re: [PATCH] tilegx-tdep: Correct aliasing errors in `tilegx_analyze_prologue'

["Maciej W. Rozycki" <macro@imgtec.com>]

On Mon, 17 Oct 2016, Pedro Alves wrote:

> > Fix a load of aliasing build errors:
> > 
> > cc1plus: warnings being treated as errors
> > .../gdb/tilegx-tdep.c: In function 'CORE_ADDR tilegx_analyze_prologue(gdbarch*, CORE_ADDR, CORE_ADDR, tilegx_frame_cache*, frame_info*)':
> > .../gdb/tilegx-tdep.c:609: error: dereferencing pointer 'operands' does break strict-aliasing rules
> > .../gdb/tilegx-tdep.c:592: error: dereferencing pointer 'operands' does break strict-aliasing rules
> > .../gdb/tilegx-tdep.c:571: error: dereferencing pointer 'operands' does break strict-aliasing rules
> > [...]
> > .../gdb/tilegx-tdep.c:601: error: dereferencing pointer '<anonymous>' does break strict-aliasing rules
> > .../gdb/tilegx-tdep.c:601: note: initialized from here
> > cc1plus: error: dereferencing pointer 'operands' does break strict-aliasing rules
> > cc1plus: error: dereferencing pointer 'operands' does break strict-aliasing rules
> > .../gdb/tilegx-tdep.c:452: note: initialized from here
> > cc1plus: error: dereferencing pointer 'pretmp.896' does break strict-aliasing rules
> > cc1plus: note: initialized from here
> > cc1plus: error: dereferencing pointer 'pretmp.896' does break strict-aliasing rules
> > cc1plus: note: initialized from here
> > make[1]: *** [tilegx-tdep.o] Error 1
> > 
> > from an attempt to cast a `long long' pointer to an `int64_t' pointer, 
> > which may not necessarily be compatible types.  Use the `long long' type 
> > for the auxiliary variable then as this is the type of the structure 
> > member referred.
> > 
> > 	gdb/
> > 	* tilegx-tdep.c (tilegx_analyze_prologue): Use the `long long' 
> > 	type for `operands'.
> > ---
> > Hi,
> > 
> >  This was discovered in an `--enable-targets=all' `mips-mti-linux-gnu' 
> > build and may be dependent on the host type and compiler version, which 
> > are `x86_64-linux' and 4.4.7 here, respectively.  OK to apply?
> > 
> 
> Sure, please do ahead.
> 
> I'd be better if tilegx.h used uint32_t/uint64_t, etc,
> but that can always be done separately by someone motivated.

 The issue there is `tilegx.h' is shared with binutils which have not yet 
moved past C89 I believe.  Of course the use of `long long' is already 
non-C89, however it's been there with some C89 compilers before `stdint.h' 
types have been introduced.  We could use `bfd_uint64_t' instead, but that 
would make `tilegx.h' depend on a BFD header.  So it's not an obvious call 
and therefore I agree it's best left to someone who has an actual interest 
with the target.

 Committed now, thanks for your review.

  Maciej