From: mordor.nospam@fly.srk.fer.hr
On 2012-06-06, Thomas Richter wrote:
>>
>> You can wrap the relevant (not-yet-destructed) part of the object
>> into the exception object and try to deal with it in catch.
>
> And where take you this object from? After all, its construction
> might also trigger an exception, let it be due to memory exhaustion.
>
We're drifting off: you can ask the same question for each throw
statement in your program.
> least the stack is unwound, so objects on the stack are most
> certainly gone. Objects on the heap might or might not go, but what
If the objects on the heap *do* get deallocated, then everything is
well: the relevant data is copied into the exception object.
>> You can copy the relevant part of the object and pass it as the
>> part of the exception.
>
> Where to?
To the catch() site.
>> STL is thus an example of using exceptions as "always on" substitute
>> for assert().
> Sorry - no, that's simply not correct. I don't know what your
> implementation does, but that is surely not required by the specs for
> operator[].
I'm not talking about operator[] -- I'm talking about many other
methods, for example, basic_string::insert overloads in gcc 4.1.2
throw std::out_of_range when given invalid indices.
> object. So what exactly does this mean? The object didn't want to
> die, so the attempt to delete it wasn't justified. Wait a minute -
The object *discovered* it didn't want to die. Agreed, this is
better handled by ordinary methods.
> What can do you about a failing fclose() in first place?
Depends. Writing data to another location might be an option,
for example.
> If you *must* deal with errors, then
>
> {
> fstream f;
>
> try {
> ... do all the file operations...
> f.close(); // I'm done
> } catch(...) {
> // handle my errors
> }
> }
>
This solution won't work if some of the "file operations" throws.
(e.g., all file-operations succeed, but you presumably do something
with that data and this "something" throws.) Where do you put the
close() that won't get executed and that might *still* throw?
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