On Wednesday, 29 September 2021 at 12:15:30 UTC, Steven
Schveighoffer wrote:
On 9/29/21 6:57 AM, JN wrote:
What makes the difference on whether a crash stacktrace gets
printed or not?
Sometimes I get a nice clean stacktrace with line numbers,
sometimes all I get is "segmentation fault error -1265436346"
(pseudo example) and I need to run under debugger to get the
crash location.
segmentation faults are memory access errors. It means you are
accessing a memory address that is not valid for your
application. If you are accessing the wrong memory, it means
something is terribly wrong in your program.
Note that on Windows in 32-bit mode, I believe you get a stack
trace. On Linux, there is the undocumented
`etc.linux.memoryhandler` which allows you to register an
error-throwing signal handler.
Signals are not really easy to deal with in terms of properly
throwing an exception. This only works on Linux, so I don't
know if it's possible to port to other OSes. I've also found
sometimes that it doesn't work right, so I only enable it when
I am debugging.
-Steve
You might also mention that even if you had a stacktrace where
the error happened, that's usually not where the error was
caused. It's most likely a completely different place in the code.
The only time where you somewhat can be sure where it happens is
when you try to access ex. a reference type that hasn't been
instantiated.
That's why in languages like C# you don't get a segfault/access
violation, but you get a NullReferenceException.
It's not a concept D has, so it defaults to segfault/access
violation.
Which means you're in really deep water when you encounter one
because you have no idea what caused it and where it was caused.
