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Re: [PATCH, PR 57748] Check for out of bounds access

On Sun, Sep 15, 2013 at 6:55 PM, Bernd Edlinger
<> wrote:
> Hello Richard,
> attached is my second attempt at fixing PR 57748. This time the movmisalign
> path is completely removed and a similar bug in the read handling of misaligned
> structures with a non-BLKmode is fixed too. There are several new test cases for the
> different possible failure modes.
> This patch was boot-strapped and regression tested on  x86_64-unknown-linux-gnu
> and i686-pc-linux-gnu.
> Additionally I generated eCos and an eCos-application (on ARMv5 using packed
> structures) with an arm-eabi cross compiler, and looked for differences in the
> disassembled code with and without this patch, but there were none.
> OK for trunk?

I agree that the existing movmisaling path that you remove is simply bogus, so
removing it looks fine to me.  Can you give rationale to

@@ -4773,6 +4738,8 @@ expand_assignment (tree to, tree from, b
          if (MEM_P (to_rtx)
              && GET_MODE (to_rtx) == BLKmode
              && GET_MODE (XEXP (to_rtx, 0)) != VOIDmode
+             && bitregion_start == 0
+             && bitregion_end == 0
              && bitsize > 0
              && (bitpos % bitsize) == 0
              && (bitsize % GET_MODE_ALIGNMENT (mode1)) == 0

and especially to

@@ -9905,7 +9861,7 @@ expand_expr_real_1 (tree exp, rtx target
                          && modifier != EXPAND_STACK_PARM
                          ? target : NULL_RTX),
-                        modifier == EXPAND_SUM ? EXPAND_NORMAL : modifier);
+                        EXPAND_MEMORY);

        /* If the bitfield is volatile, we want to access it in the
           field's mode, not the computed mode.

which AFAIK makes "memory" expansion of loads/stores from/to registers
change (fail? go through stack memory?) - see handling of non-MEM return
values from that expand_expr call.

That is, do you see anything break with just removing the movmisalign path?
I'd rather install that (with the new testcases that then pass) separately as
this is a somewhat fragile area and being able to more selectively
would be nice.


> Regards
> Bernd.

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