Given that we can't guarantee that Exim contains no further bugs enabling stack 
overflows, I wondered if it would be wise to add stack protection to the 
default build?

In Linux this would appear to be a simple case of adding  -fstack-protector-all 
(or -fstack-protector) to CFLAGS in OS/Makefile-Linux

CFLAGS=-O -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -fstack-protector-all

The obvious drawback is that older systems do not support this (I believe it 
requires at least gcc 4.1). It may also have performance implications or other 
subtler drawbacks of which I am not aware.

Is there any experience on the list of this? 

Is it a good idea?

Are there other similar measures we could take to increase the resilience of 
the default build to potential exploits?

Neil Youngman
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