Re: Merging feature/android

[Arsen Arsenović]

Po Lu <luangruo@yahoo.com> writes:

> Arsen Arsenović <arsen@aarsen.me> writes:
>
>> -fexceptions is useful if it is possible to get a call stack which
>> invokes C++ through a C function through a C++ function, for instance,
>> if the comparator of a qsort could throw.  This provides the user of a
>> given C API to gracefully handle thrown errors.  Alternatively, it also
>> allows the C API developers to (mostly) gracefully clean up when a C++
>> exception remains uncaught.  This is why libc is compiled with
>> -fexceptions for instance.
>>
>> __attribute__((cleanup)) will run cleanups during stack unwinding:
>
> Only if you build Emacs with -fexceptions.
>
>> ‘cleanup (CLEANUP_FUNCTION)’
>>      The ‘cleanup’ attribute runs a function when the variable goes out
>>      of scope.  This attribute can only be applied to auto function
>>      scope variables; it may not be applied to parameters or variables
>>      with static storage duration.  The function must take one
>>      parameter, a pointer to a type compatible with the variable.  The
>>      return value of the function (if any) is ignored.
>>
>>      If ‘-fexceptions’ is enabled, then CLEANUP_FUNCTION is run during
>>      the stack unwinding that happens during the processing of the
>>      exception.  Note that the ‘cleanup’ attribute does not allow the
>>      exception to be caught, only to perform an action.  It is undefined
>>      what happens if CLEANUP_FUNCTION does not return normally.
>>
>> IMO, the price of exceptions is overblown, so it could be worthwhile
>> adopting this, if I understand the context right.
>
> If a C++ exception is thrown inside a module function, then we should
> IMO just let everything blow up.  How are they different from any other
> kind of unexpected error in a dynamic module, such as for instance an
> arithmetic trap, memory access error, or perhaps a Pascal exception?

I agree that it is unnecessary to support them.  The context that I took
to understand is specifically wanting to support C++ modules.  If that
is not the case, then -fexceptions is not worth enabling, indeed.
-- 
Arsen Arsenović

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