Re: [PATCH 4/7] Fix invalid left shift of negative value.

[Dominik Vogt <vogt at linux dot vnet dot ibm dot com>]

On Fri, Oct 30, 2015 at 03:42:41PM +0100, Dominik Vogt wrote:
> On Fri, Oct 30, 2015 at 03:38:15PM +0100, Dominik Vogt wrote:
> > The following series of patches fixes all occurences of
> > left-shifting negative constants in C code which is undefined by
> > the C standard.  The patches have been tested on s390x, covering
> > only a small subset of the changes.
> 
> Changes in gdb/.

Any opinions on this patch?

> gdb/ChangeLog
> 
> 	* hppa-tdep.c (hppa_sign_extend, hppa_low_hppa_sign_extend)
> 	(prologue_inst_adjust_sp, hppa_frame_cache): Fix left shift of negative
> 	value.
> 	* dwarf2read.c (read_subrange_type): Likewise.

> >From 54f1c95e0993fb21ecb47638efa9762816fd95c6 Mon Sep 17 00:00:00 2001
> From: Dominik Vogt <vogt@linux.vnet.ibm.com>
> Date: Fri, 30 Oct 2015 15:17:22 +0100
> Subject: [PATCH 4/7] gdb: Fix left shift of negative value.
> 
> ---
>  gdb/dwarf2read.c | 2 +-
>  gdb/hppa-tdep.c  | 8 ++++----
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
> index 87dc8b4..48921e7 100644
> --- a/gdb/dwarf2read.c
> +++ b/gdb/dwarf2read.c
> @@ -15048,7 +15048,7 @@ read_subrange_type (struct die_info *die, struct dwarf2_cu *cu)
>       the bounds as signed, and thus sign-extend their values, when
>       the base type is signed.  */
>    negative_mask =
> -    (LONGEST) -1 << (TYPE_LENGTH (base_type) * TARGET_CHAR_BIT - 1);
> +    -((LONGEST) 1 << (TYPE_LENGTH (base_type) * TARGET_CHAR_BIT - 1));
>    if (low.kind == PROP_CONST
>        && !TYPE_UNSIGNED (base_type) && (low.data.const_val & negative_mask))
>      low.data.const_val |= negative_mask;
> diff --git a/gdb/hppa-tdep.c b/gdb/hppa-tdep.c
> index ba7f946..3206729 100644
> --- a/gdb/hppa-tdep.c
> +++ b/gdb/hppa-tdep.c
> @@ -104,7 +104,7 @@ static const struct objfile_data *hppa_objfile_priv_data = NULL;
>  static int
>  hppa_sign_extend (unsigned val, unsigned bits)
>  {
> -  return (int) (val >> (bits - 1) ? (-1 << bits) | val : val);
> +  return (int) (val >> (bits - 1) ? (-(1 << bits)) | val : val);
>  }
>  
>  /* For many immediate values the sign bit is the low bit!  */
> @@ -112,7 +112,7 @@ hppa_sign_extend (unsigned val, unsigned bits)
>  static int
>  hppa_low_hppa_sign_extend (unsigned val, unsigned bits)
>  {
> -  return (int) ((val & 0x1 ? (-1 << (bits - 1)) : 0) | val >> 1);
> +  return (int) ((val & 0x1 ? (-(1 << (bits - 1))) : 0) | val >> 1);
>  }
>  
>  /* Extract the bits at positions between FROM and TO, using HP's numbering
> @@ -1357,7 +1357,7 @@ prologue_inst_adjust_sp (unsigned long inst)
>  
>    /* std,ma X,D(sp) */
>    if ((inst & 0xffe00008) == 0x73c00008)
> -    return (inst & 0x1 ? -1 << 13 : 0) | (((inst >> 4) & 0x3ff) << 3);
> +    return (inst & 0x1 ? -(1 << 13) : 0) | (((inst >> 4) & 0x3ff) << 3);
>  
>    /* addil high21,%r30; ldo low11,(%r1),%r30)
>       save high bits in save_high21 for later use.  */
> @@ -2066,7 +2066,7 @@ hppa_frame_cache (struct frame_info *this_frame, void **this_cache)
>  		CORE_ADDR offset;
>  		
>  		if ((inst >> 26) == 0x1c)
> -		  offset = (inst & 0x1 ? -1 << 13 : 0)
> +		  offset = (inst & 0x1 ? -(1 << 13) : 0)
>  		    | (((inst >> 4) & 0x3ff) << 3);
>  		else if ((inst >> 26) == 0x03)
>  		  offset = hppa_low_hppa_sign_extend (inst & 0x1f, 5);
> -- 
> 2.3.0
> 



Ciao

Dominik ^_^  ^_^

-- 

Dominik Vogt
IBM Germany