On Tuesday, 20 October 2020 at 16:58:12 UTC, Severin Teona wrote:
Hi guys.
I have a curiosity, regarding [1] - I had encountered some
"undefined reference" errors when trying to link the druntime
(compiled for an embedded architecture) without some
implementation of the POSIX thread calls (and other stuff too).
First, keep in mind that druntime and Phobos depends heavily on
the C standard library, the Posix APIs, Windows APIs and other
platform specific APIs. There's no list of what features or APIs
need to be supported by a platform. There's no general concept of
optional platform features, i.e. druntime will not automatically
adopt if your platform doesn't support a specific feature (like
threads). For example, on iOS (and related platforms)
`std.process` is not supported (because you're not allowed to
call `fork`). This is just hardcoded: if the platform is iOS,
don't provide `std.process`.
What I'm saying, if you modify druntime to remove threads and
locks, and resolve your undefined references, you might end up
with new undefined references for other symbols.
My curiosity is what would change if I removed from the
druntime everything that has to do with mutexes or threads.
Would it be possible for the druntime to run and work properly
on a microcontroller - where those concepts are not necessary?
Could I just remove everything about synchronisation from the
druntime, and classes or Garbage Collector to still work
properly?
The garbage collector will probably work (if you remove the
interaction with threads from it). Classes are a bit more
complicated, they have a hidden monitor field [1]. There's also
the concept of synchronized classes [2]. There's also the
`synchronized` statement [3]. All these depend on
mutex/monitors/locks in some form (I don't know exactly how the
implementation works). Hopefully it should be fine as long as
your code doesn't use the `synchronized` statement or
synchronized classes. But all classes do come with a hidden
monitor field.
[1] https://dlang.org/spec/abi.html#classes
[2] https://dlang.org/spec/class.html#synchronized-classes
[3] https://dlang.org/spec/statement.html#synchronized-statement
--
/Jacob Carlborg
