Forgive me, but I don't see where anything is guaranteed to be zero'd
before use. I'm likely wrong somewhere since you disagree.
http://en.wikipedia.org/wiki/.bss
This is about what happens to work, and specifically notes that it is
not part of the C standard. There is a big difference between programs
that obey the standard, and those that don't but happen to work on some
systems. The latter programs have latent bugs that can definitely
cause trouble.
A properly written C program should avoid uninitialized variables, just
as a properly written Ada program should avoid them.
In GNAT, we have found the Initialize_Scalars pragma to be very useful
in finding uninitialized variables. It causes all scalars to be
initialized using a specified bit pattern that can be specified at
link time, and modified at run-time.
If you run a program with different patterns, it should give the same
result, if it does not, you have an uninitialized variable or other
non-standard aspect in your program which should be tracked down and
fixed.
Note that the BSS-is-always-zero guarantee often does not apply when
embedded programs are restarted, so it is by no means a universal
guarantee.
