nothrow function callbacks in extern(C) code - solution

[Rainer Schuetze via Digitalmars-d]

On 22.06.2014 02:23, Andrei Alexandrescu wrote:
> On 6/20/14, 3:14 AM, Rainer Schuetze wrote:
>> We either have to be more conservative with annotating OS functions or
>> relax the guarantees of nothrow or @nogc. Both alternatives are not very
>> compelling.
>
> Callbacks passed into OS/clib functions are never supposed to throw so
> we must annotate them all with nothrow. C functions are never designed
> under the assumption callbacks may throw. -- Andrei

For nothrow that restriction makes sense, though there are functions in 
the Windows "C API" that actually may throw, e.g. HeapAlloc [1] and 
MmProbeAndLockPages [2]. No callbacks are involved in these examples, 
though.
Under unix, signal handlers that throw exceptions seem to be used, 
though this might be non-standard. We even have one in druntime [3].

I'm ok with the current treatment of nothrow, but what can we do about 
@nogc?


[1] 
http://msdn.microsoft.com/en-us/library/windows/desktop/aa366597%28v=vs.85%29.aspx
[2] 
http://msdn.microsoft.com/en-us/library/windows/hardware/ff554664%28v=vs.85%29.aspx
[3] 
https://github.com/D-Programming-Language/druntime/blob/master/src/etc/linux/memoryerror.d

BTW: The D exception handling is compatible with SEH for Win32, but not 
for Win64. You cannot handle exceptions by type across languages, 
though, only unwinding and "catch(Throwable)" works here.