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Re: memcpy on overlapping memory
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From: |
Bruno Haible |
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Subject: |
Re: memcpy on overlapping memory |
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Date: |
Sat, 20 Aug 2022 06:25:55 +0200 |
Mark Esler wrote:
> I believe Gnulib contains memcpy calls on overlapping memory and that
> commit 3e7178b337e3a83df9e4f36a4aef516f089e3796 was incomplete.
>
> Please see https://gitlab.com/gsasl/gsasl/-/issues/4 for details.
The comment from [1] is correct.
Your statement "If left_over >= 16, memcpy will overwrite the source
as it is being copied." is incorrect.
ctx->buffer and &ctx->buffer[16] differ by 16 units, each unit being
uint32_t, that is 4 bytes wide. So these pointers differ by 64 bytes.
Since left_over ≤ 64, there is no overlap.
Bruno
[1]
https://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commitdiff;h=3e7178b337e3a83df9e4f36a4aef516f089e3796