Guilhem Moulin dixit: >first to report it I suppose nobody uses large offset= values. Don't >think adding ‘Depends: bc’ is justified here :-P.
Eh, bc’s supposed to be a base tool anyway… >Also in practice I was able to use offset=2⁵⁹ (buster-i386)tglase@tglase:~ $ echo '2^59' | bc 576460752303423488 (buster-i386)tglase@tglase:~ $ echo $(($(echo '2^59' | bc)*512)) 0 (buster-i386)tglase@tglase:~ $ bash bash$ echo $(($(echo '2^59' | bc)*512)) 0 I’d not call this “use”. > with bash, dash, klibc's sh and busybox's sh mksh is also a viable /bin/sh (the /bin/lksh binary), and for that I speak as developer ;) >I'll just ignore the potential overflow. I'll just make the script >choke when the arithmetic operation fails. That’s the problem: the operation does not fail, it “only” overflows. Overflowing *is* permitted (by C UB rules) to do “rm -rf /” even if GCC does not (yet) do that… but even if it wraps around, you get the WRONG values (see above). (buster-i386)tglase@tglase:~ $ lksh -c 'echo $(($(echo "2^40" | bc)*512))' 0 (This is actually what POSIX requires. So bash, dash, etc. are actually noncompliant on 32-bit platforms.) So please, if you’re going to “ignore” this in practice, at least install the code that checks for offset ≤ 4194303. I can provide a corresponding patch, if you want. bye, //mirabilos -- FWIW, I'm quite impressed with mksh interactively. I thought it was much *much* more bare bones. But it turns out it beats the living hell out of ksh93 in that respect. I'd even consider it for my daily use if I hadn't wasted half my life on my zsh setup. :-) -- Frank Terbeck in #!/bin/mksh
