Hi Mark, On Sat, 11 May 2019 04:03:41 -0400 Mark H Weaver wrote: > Hmm. What makes you think that 'invoke' swallowed the output? You > might be right, but 'invoke' is used quite widely by now in Guix, > including to invoke 'make' in gnu-build-system, and I haven't seen > reports of it swallowing output. I found out what was up with invoke. The child process didn't output anything on stdout or stderr, but it died with SIGFPE and I either was unable to interpret invoke's exception properly, or it didn't say (probably the former). It seems that mrustc uses a different gcc version than rust 1.19 which seems to be a bad idea to me, but not sure whether it's the cause of the SIGFPE.