Inside a signal handler, you cannot allocate memory because the signal
handler, being implemented with a C
[`signal`](https://en.cppreference.com/w/c/program/signal) call, can be
called _during_ a memory allocation - when that happens, the CTRL-C
handler causes a segfault and/or other inconsistent state.
Similarly, the call can happen from a non-nim thread or inside a C
library function call etc, most of which do not support reentrancy and
therefore cannot be called _from_ a signal handler.
The stack trace facility used in the default handler is unfortunately
beyond fixing without more significant refactoring since it uses
garbage-collected types in its API and implementation.
As an alternative to https://github.com/nim-lang/Nim/pull/25110, this PR
removes the most problematic signal handler, namely the one for SIGINT
(ctrl-c) - SIGINT is special because it's meant to cause a regular
shutdown of the application and crashes during SIGINT handling are both
confusing and, if turned into SIGSEGV, have downstream effects like core
dumps and OS crash reports.
The signal handlers for the various crash scenarios remain as-is - they
may too cause their own crashes but we're already going down in a bad
way, so the harm is more limited - in particular, crashing during a
crash handler corrupts `core`/crash dumps. Users wanting to keep their
core files pristine should continue to use `-d:noSignalHandler` - this
is usually the better option for production applications since they
carry more detail than the Nim stack trace that gets printed.
Finally, the example of a ctrl-c handler performs the same mistake of
calling `echo` which is not well-defined - replace it with an example
that is mostly correct (except maybe for the lack of `volatile` for the
`stop` variable).
(cherry picked from commit 41ce86b577)
* quit value gets saturated to ranges
* add documentation
* minimal changes
* refactor
* small fix
* add documentation
* fixes
* Update lib/system.nim
Co-authored-by: Juan Carlos <juancarlospaco@gmail.com>
Co-authored-by: Juan Carlos <juancarlospaco@gmail.com>
* fixes overloading resolution for passing owned(Future[string]) to Future[T]
* WIP: make --newruntime work with .async
* memtracker: make it compile again
* make Nimble compile again
