Lines queued behind the logger were lost when the process ended through
abort(), std::terminate, the Windows crash report or a guest _Exit,
because only driver failure, Driver::stop and a normal exit flushed the
queue.
libc keeps one end flush (LibcSetEndFlush_nid_no_patch) and runs it from
those paths. Its first registration chains a SIGABRT handler in front of
the previous one, so every abort() and std::terminate in the process is
covered, on Linux as well; with the default disposition the handler
restores it and raises again, so raise(SIGABRT) still ends the process.
Guest abort() and _Exit, and ReportCrash for the first fatal exception,
run the flush directly. AsyncLog registers a bounded flush (FlushFor, 2 s)
that polls two counters and takes no lock, so a dying process cannot hang
on a blocked stream or on the queue lock; after its first timeout it
returns at once. Flush counts queued and finished entries instead of
watching the queue and the writer flag, so it waits for the lines queued
before the call and not for a moment in which no thread is logging.
agc_async_log_fatal runs the test executable as a child that queues lines
behind a held stream and ends in abort(), std::terminate(), raise(SIGABRT)
(POSIX) or an access violation (Windows), and once more with the stream
never released. The lines of the first four must arrive in order, the last
child must end after the bound, and every child has a watchdog.
agc_async_log gains the bounded flush case.
Flush must not return while the logger still waits for a stream that
another thread holds (the regression reported on the pull request: it gave
up after two seconds), and a full queue must block its caller instead of
dropping a line. AsyncLog::Capacity becomes public so the test sizes its
load from it.
Texture creation logged one stdout line per texture and per mip through
WriteLogLine, which formatted with the mingw printf and flushed every
line on the queue worker (about 786k lines in a 25 minute cave run).
AsyncLog keeps a bounded queue and a logger thread. AGC_LOG_DEFERRED
captures numeric arguments on the caller and formats them on the logger
thread; WriteLogLine hands finished lines to a per-module sink in
libc/LogMacros.hpp that AgcDriver installs, so all AgcDriver stdout
lines keep their order and are written one flush per batch. A full queue
blocks the caller, so no line is dropped. Flush runs on driver failure,
shutdown and at exit. APS5_LOG_SYNC=1 restores the synchronous path.
Identical "deferred write-back failed" notes are printed three times per
10 s and then counted into one "repeated N more times" line. A
"[log] 10 s" line reports lines, bytes, caller time and logger time
(APS5_LOG_STATS=0 hides it).
AlxcBTW