memcpy overlap: quickly detect, diagnose, work around

[Nicholas Miell]

On 11/28/2010 03:13 PM, John Reiser wrote:
> The option to check is controlled by an environment variable
> MEMCPY_CHECK_ which influences choices made by __init_cpu_features
> and the STT_GNU_IFUNC mechanism for choosing alternate implementations
> at runtime.

If you're going to control it via an environment variable, why not just
make a LD_PRELOADed shared library which intercepts memcpy() in the
usual manner?

Doing it that way has the added benefit that anybody could use it
immediately, without needing to replace their glibc with a patched
version that will never get merged upstream.