Re: Change in wireshark[master]: USB: do not take into account implicit structure alignment i...

[Guy Harris <guy () alum mit edu>]

On Jan 15, 2015, at 1:54 PM, "Pascal Quantin (Code Review)" <code-review-do-not-reply () wireshark org> wrote:

> Pascal Quantin has uploaded a new change for review.
>
>  https://code.wireshark.org/review/6560
>
> Change subject: USB: do not take into account implicit structure alignment in USB address size
> ......................................................................
>
> USB: do not take into account implicit structure alignment in USB address size

"Compound" addresses, constructed from multiple non-contiguous components, are beginning to be a bit of a problem; 
Michael Mann's recent changes exposed the underlying problem with them, namely that we're using C data structures as 
the address data for them, and C data structures might have padding between elements and the end, and

        1) we do memcmp()-based comparisons on address data in, for example, hash tables

and

        2) setting individual structure members from the components of the address doesn't set the padding, so you get 
valgrind warnings that can reflect real problems (wherein two addresses that are the same don't compare equal) - I 
checked in my changes because a regression test showed some captures being dissected differently because one version of 
TShark found conversation matches and another version didn't, for the same capture.

Using wmem_new0() on them didn't seem to squelch the valgrind complaints; if we need to do more, perhaps that's a sign 
that we need a better way to handle "compound" addresses than stuffing them into C data structures.  I don't know what 
the better way would be - just packing them into what amount to packed structures, for example?  (No, GCC's keywords 
for declaring structures packet don't suffice, as not all compilers used to compile Wireshark are GCC-compatible.)
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