This adds an "in-process" interpretation of dup2s, allowing for fish to
output directly to the correct file descriptor without having to perform
an in-kernel dup2 sequence.
The sigchld generation expresses the idea that, if we receive a sigchld
signal, the generation will be different than when we last recorded it. A
process cannot exit before it has launched, so check the generation count
before process launch. This is an optimization that reduces failing
waitpid calls.
This is a big change to how process reaping works, reimplenting it using
topics. The idea is to simplify the logic in
process_mark_finished_children around blocking, and also prepare for
"internal processes" which do not correspond to real processes.
Before this change, fish would use waitpid() to wait for a process group,
OR would individually poll processes if the process group leader was
unreapable.
After this change, fish no longer ever calls blocking waitpid(). Instead
fish uses the topic mechanism. For each reapable process, fish checks if
it has received a SIGCHLD since last poll; if not it waits until the next
SIGCHLD, and then polls them all.
topic_monitor allows for querying changes posted to one or more topics,
initially sigchld. This will eventually replace the waitpid logic in
process_mark_finished_children().
Comment from the new header:
Topic monitoring support. Topics are conceptually "a thing that can
happen." For example, delivery of a SIGINT, a child process exits, etc. It
is possible to post to a topic, which means that that thing happened.
Associated with each topic is a current generation, which is a 64 bit
value. When you query a topic, you get back a generation. If on the next
query the generation has increased, then it indicates someone posted to
the topic.
For example, if you are monitoring a child process, you can query the
sigchld topic. If it has increased since your last query, it is possible
that your child process has exited.
Topic postings may be coalesced. That is there may be two posts to a given
topic, yet the generation only increases by 1. The only guarantee is that
after a topic post, the current generation value is larger than any value
previously queried.
Tying this all together is the topic_monitor_t. This provides the current
topic generations, and also provides the ability to perform a blocking
wait for any topic to change in a particular topic set. This is the real
power of topics: you can wait for a sigchld signal OR a thread exit.
This resolves the issue where running pre-compiled Linux packages from
binary package manager repositories lead fish to think that we are not
running under WSL.
- Closes#5619.
- Ping neovim/neovim#7330
This happens on OpenIndiana/Solaris/Illumos/SunOS.
Elsewhere we use read_blocked, which already returned in this
case (and which we might want to use here as well!).
`fish_title` as invoked by fish itself is not running in an interactive
context, and attempts to read from the input fd (e.g. via `read`) cause
fish to segfault, go into an infinite loop, or hang at the read prompt
depending on the exact command line and fish version.
This patch addresses that by explicitly closing the input fd when
invoking `fish_title`.
Reported by @floam in #5629. May close that issue, but situation is
unclear.
Taking advantage of the maybe_t's, the logic and nesting here
can be a bit less intense.
Small adjustments to debug output, and found a more accurate
version number for Lion Terminal.app.
Longer term we should have a terminal_t class or something
encapsulating all the kinds of terminal detection we have
with methods that return the color support, and also stuff
like whether the terminal has the newline glitch, the
ambiguous width character behavior, etc.
fish forks child processes when (for example) writing out builtin output.
After fork it resets signal handlers, but if a signal is delivered before
the signal handlers are reset, it will inherit fish's default handlers,
which do things like swallow SIGINT. Teach fish's default signal handlers
to detect this case and re-raise signals with default handlers.
This improves the reliability of control-C in the face of builtins.
I hope this is now complete.
Also, shorten enough descriptions to make `string match --<TAB>`
show a two column pager with 80 cols.
We really should have shown more retraint in the design of `string`,
not all of the flags required both a long and short option created.
300ms was waaay too long, and even 100ms wasn't necessary.
Emacs' evil mode uses 10ms (0.01s), so let's stay a tad higher in case
some terminals are slow.
If anyone really wants to be able to type alt+h with escape, let them
raise the timeout.
Fixes#3904.
`/tmp` isn't present / writeable on every system. Instead of always
using `/tmp`, try to use standard environment variables and
configuration to find a temporary directory.
Adapted from #3974, with updates based on those comments.
Closes#3845.
