Fixing the glibc adobe flash incompatibility

Chris Adams cmadams at
Wed Nov 17 22:38:01 UTC 2010

Once upon a time, Gregory Maxwell <gmaxwell at> said:
> But is it only me who worries that lots of people are running code
> exposed to the internet that has obviously never even been run under
> valgrind?

Yeah, people are acting like Adobe Flash is the only program in the
world to make this (unfortunately quite easy) mistake.  ISTR some old
configure scripts (the rn/trn/perl one maybe?) that actually checked
memcpy's overlap behavior at compile time.  Somebody else has already
reported finding another program (in the Fedora distribution even) that
suffered from the same problem.

Yes, by standards, memcpy is free to explode the universe if you call it
with overlapping source and destination.  It doesn't mean it is the
right thing to do, especially for a limited performance gain (and only
on certain CPUs).  Changing its behavior is an ABI change, even if an
undocumented one.

Chris Adams <cmadams at>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.

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