Introduce a new strategy for notifying other fish processes of universal
variable changes, as a planned replacement for the complex
strategy_named_pipe. The new strategy still uses a named pipe, but instead
of select() on it, it arranges for SIGIO to be delivered when data is
available. If a SIGIO has been seen since the last check, it means the file
needs to be re-read.
The topic monitor allows a client to wait for multiple events, e.g. sigchld
or an internal process exit. Prior to this change a client had to specify
the list of generations and the list of topics they are interested in.
Simplify this to just the list of generations, with a max-value generation
meaning the topic is not interesting.
Also remove the use of enum_set and enum_array, it was too complex for what
it offered.
When fish receives a "cancellation inducing" signal (SIGINT in particular)
it has to unwind execution - for example while loops or whatever else that
is executing. There are two ways this may come about:
1. The fish process received the signal
2. A child process received the signal
An example of the second case is:
some_command | some_function
Here `some_command` is the tty owner and so will receive control-C, but
then fish has to cancel function execution.
Prior to this change, these were handled uniformly: both would just set a
cancellation signal inside the parser. However in the future we will have
multiple parsers and it may not be obvious which one to set the flag in.
So instead distinguish these cases: if a process receives SIGINT we mark
the signal in its job group, and if fish receives it we set a global
variable.
We were previously aborting the main event loop before calling fish_exit
in the event of a SIGHUP. This patch causes the SIGHUP to be stored in a
separate state variable from a regular "must exit" condition so the
associated event can be fired before we terminate the loop.
All streams are redirected before the event is called to prevent a
SIGTTIN/SIGTTOU due to the user script reading/writing from a disposed
tty.
Closes#7014
This makes it possible to expand the signals checked by the type. I can't merge
the sigttin fixes for #7060 yet because they introduce new breakage, but this
will make merging any future fix easier.
Finish the transition to termsize.h. Remove the scary termsize bits
from common.cpp, which can throw off events at arbitrary calls and are
dangerously reentrant. Migrate everyone to the new termsize.h.
fish's handling of terminal sizes is currently rather twisted. The
essential problem is that the terminal size may change at any point from a
SIGWINCH, and common_get_{width,height} may modify it and post variable
change events from arbitrary locations.
Tighten up the semantics. Assign responsibility for managing the tty size
to a new class, `termsize_container_t`. Rationalize locking and reentrancy.
Explicitly nail down the relationship between $COLUMNS/$LINES and the tty
size. The new semantics are: whatever changed most recently takes
precendence.
When fish exits, it tries to restore the foreground process group.
However this may actually steal control of the fg process group
from another process. Fix this by clearing the SIGTTOU handler so
that tcsetpgrp() will fail.
Credit to @mqudsi for awesome debugging.
Fixes#7060
We used to have a global notion of "is the shell interactive" but soon we
will want to have multiple independent execution threads, only some of
which may be interactive. Start tracking this data per-parser.
Prior to this diff, fish had different signal handling functions for
different signals. However it was hard to coordinate when a signal needed
to be the default handler, and when it was custom. In #5962 we overwrote
fish's custom WINCH handler with the default_handler when fish script asked
for WINCH to be handled.
Just have a single big signal handler function. That way it can never be
set to the wrong thing.
Fixes#5969
Now that our interactive signal handlers are a strict superset of
non-interactive ones, there is no reason to "reset" signals or take action
when becoming non-interactive. Clean up how signal handlers get installed.
The signal handlers for interactive and non-interactive SIGINT were distinct
and talked to the reader. This wasn't really justified and will complicate
having multiple threads. Unify these into a single signal handler.
This runs build_tools/style.fish, which runs clang-format on C++, fish_indent on fish and (new) black on python.
If anything is wrong with the formatting, we should fix the tools, but automated formatting is worth it.
fish's signal handlers are now sufficiently innocuous that there should
be no reason to block signals (outside of temporarily, when creating a
thread and we need to manipulate the signal mask).
Prior to this fix, fish had a signal_list_t that accumulated signals.
Signals were added to an array of integers, with an overflow flag.
The event machinery would attempt to atomically "swap in" the other list.
After this fix, there is a single list of pending signal events, as an array
of atomic booleans. The signal handler sets the boolean corresponding to its
signal.
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.
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.
Prior to this fix, fish would swallow SIGINT in non-interactive mode. This
meant that scripts could only be Ctrl-C'd if fish was executing an external
command.
Unblock SIGINT in non-interactive mode.
Fixes#5253
Valgrind warns that the sometimes uninitialized sigaction.sa_flags field
is sometimes used when passed to the signal handler.
This patch explicitly zeros out the sigaction.sa_flags field at creation
time.
PR #3691 made most calls to `signal_block()` and `signal_unblock()`
no-ops unless a magic env var is set when fish starts running. It's
been seven months since that change was made and no problems have been
reported. This finishes that work by removing those no-op function calls
and support for the magic env var in our next major release (which won't
happen till at least six months from now).
Working on a related problem caused me to notice that if a fish script
was run via `nohup` it would die when receiving SIGHUP. This fixes the
code to handle that correctly so that fish scripts can be nohup'd.
Fixes#4007
This is the next step in determining whether we can disable blocking
signals without a good reason to do so. This makes not blocking signals
the default behavior. If someone finds a problem they can add this to
their ~/config/fish/config.fish file:
set FISH_NO_SIGNAL_BLOCK 0
Alternatively set that env var before starting fish. I won't be surprised
if people report problems. Till now we have relied on people opting in
to this behavior to tell us whether it causes problems. This makes the
experimental behavior the default that has to be opted out of. This will
give us a lot more confidence this change doesn't cause problems before
the next minor release.
Note that there are still a few places where we force blocking of
signals. Primarily to keep SIGTSTP from interfering with the shell in
response to manipulating the controlling tty. Bash is more selective
in the signals it blocks around the problematic syscalls (c.f., its
`git_terminal_to()` function). However, I don't see any value in that
refinement.
There should be just one place that calls `setupterm()`. While refactoring
the code I also decided to not make initializing the curses subsystem a
fatal error. We now try two fallback terminal names ("ansi" and "dumb")
and if those can't be used we still end up with a usable shell.
Fixes#3850
This reverts commit e30f3fee88.
Not sure why I didn't notice this before merging it but the change I'm
reverting makes it impossible to start a login shell.
This is the next step in determining whether we can disable blocking
signals without a good reason to do so. This makes not blocking signals
the default behavior. If someone finds a problem they can add this to
their ~/config/fish/config.fish file:
set FISH_NO_SIGNAL_BLOCK 0
Alternatively set that env var before starting fish. I won't be surprised
if people report problems. Till now we have relied on people opting in
to this behavior to tell us whether it causes problems. This makes the
experimental behavior the default that has to be opted out of. This will
give is a lot more confidence this change doesn't cause major problems
prior to the next minor release.
The shell was doing a log of signal blocking/unblocking that hurts
performance and can be avoided. This reduced the elapsed time for a
simple benchmark by 25%.
Partial fix for #2007
The existing code is inconsistent, and in a couple of cases wrong, about
dealing with strings that are not valid ints. For example, there are
locations that call wcstol() and check errno without first setting errno
to zero. Normalize the code to a consistent pattern. This is mostly to
deal with inconsistencies between BSD, GNU, and other UNIXes.
This does make some syntax more liberal. For example `echo $PATH[1 .. 3]`
is now valid due to uniformly allowing leading and trailing whitespace
around numbers. Whereas prior to this change you would get a "Invalid
index value" error. Contrast this with `echo $PATH[ 1.. 3 ]` which was
valid and still is.
This fixes some of the IWYU and cppcheck lint warnings. And only on
macOS (formerly OS X). Fixing these types of warnings on a broader set
of platforms should be done but this is a baby step to making `make
lint-all` have few, if any, warnings. This reduces the number of lines
in the `make lint-all` output on macOS by over 500 lines.
