On 2020-08-28, Paul Eggert <egg...@cs.ucla.edu> wrote: > On 8/28/20 6:52 AM, Zack Weinberg wrote: >> I think that for 2.70 we should make fd 0 read-only and 1,2 >> write-only here, and revisit this afterward -- when we're not in a >> release freeze we can think about things like turning on set -e mode. > > Sounds good. > > In the longer term I doubt whether set -e is the way to go. I recall some > old shells mishandling it (e.g., with 'set -e' the command 'A || B' would > cause the shell to exit when A failed). And I suspect the use of 'set -e' to > detect shell errors is problematic even today. 'set -e' is intended more as > a debugging aid than as a programming facility.
Even if the shell implements POSIX requirements with no bugs, The semantics for 'set -e' get so weird when complex commands are involved and that weirdness propagates down into shell functions in very unintuitive ways. Whether or not 'set -e' has any effect at all in a shell function body depends on the specific shell syntax used at the point of the function call! It certainly should not be enabled at the top level of configure scripts by Autoconf (or any nontrivial shell script, really) as that will just lead everyone to madness. Cheers, Nick
