guest_host_standard_error and exception_runtime fork children that end in
SIGABRT on purpose. When kernel.core_pattern pipes cores to a handler, as
Ubuntu's apport and systemd-coredump do, the kernel starts it for every
dumpable crash even with RLIMIT_CORE at 0. apport takes about 1.1 s per
crash here, so guest_host_standard_error spent 2.3 s waiting and timed out
at its 10 s limit under parallel ctest load. Marking those children
non-dumpable on Linux skips the handler: 2.29 s to 0.01 s and
1.17 s to 0.01 s, with the same SIGABRT and message checks.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
On Linux a guest stderr redirect also moves the host's: guest
descriptors are host descriptors, and the guest stderr stream wraps the
host stderr FILE. After dup2(fd, 2), or freopen(path, mode, stderr) with
full buffering, the libc terminate report, the host fprintf(stderr)
diagnostics and libstdc++'s terminate message go into the title's pipe
or file, and abort() discards what is still buffered. RetroArch
(PPSA99169) reopens stderr onto app0/trace.txt with full buffering, so
its stop on main left no message anywhere.
Before the first guest redirect of descriptor 2 (libkernel dup2, libc
freopen of a stream on descriptor 2), keep a close-on-exec duplicate of
the host descriptor 2 and point the host stderr at an unbuffered stream
on it. The guest stream keeps its own FILE and follows the redirect.
The libc terminate report writes to the kept descriptor with write()
instead of the stderr stream, and libkernel's sceKernelDebugOutText uses
the same kept descriptor.
