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[BUG] valarray_copy mask_array-related over-run
- From: Luke Kenneth Casson Leighton <lkcl at samba-tng dot org>
- To: libstdc++ at gcc dot gnu dot org
- Date: Wed, 3 Jul 2002 22:25:40 +0000
- Subject: [BUG] valarray_copy mask_array-related over-run
--- /usr/include/g++-3/std/std_valarray.h Wed Jul 3 21:49:02 2002
+++ /tmp/x Wed Jul 3 21:49:08 2002
@@ -374,7 +374,7 @@
valarray<_Tp>::operator= (const mask_array<_Tp>& __ma)
__valarray_copy (__ma._M_array, __ma._M_mask,
- _Array<_Tp>(_M_data), _M_size);
+ _Array<_Tp>(_M_data), __ma._M_sz);
when used as follows:
b = false;
b = true;
b = true;
b = false;
i = 99;
i = i[b];
the number of items copied due to the assignment
of the mask_array created by the operator is FOUR.
actually, it's a heck of a lot more than four, because
the loop starting at line 56 of valarray_meta.tcc over-runs
looking for (4-2) more randomly-set bools that are true,
in uninitialised memory. __p gets advanced well into
the only reason i noticed this is because i was using a
rather complex class of
and it obviously attempted to create a copy constructor
from a complete garbage memory address of 0x101 as it
advanced __p too far down the array.
[it's for an emulator of a parallel processor version of
valarray, where the parallel processor is a 4096 one-bit-serial
monster. therefore i need to emulate N-bit addition and
therefore parallel N-bit addition :) :)]
is this an already-discovered bug?
am i correct in the usage of this code?
please confirm, bug or no.
also appreciated acknowledgement of msg received.
p.s. patches accepted to get valarray and valarray_meta to
use a common array class containing _M_data and _M_size?
there is a lot of duplicated code between the two.
i need to be able to easily patch in a different memory
model, and at the moment i will have to patch it in
in _two_ separate places, it's a bit of a mess.
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