[LLVMdev] Making LLVM safer in out-of-memory situations

[Philip Reames]

On 12/13/13 6:47 AM, Becker, Philipp wrote:
> Hi Hal,
>
>> Does this mean that you're using C++ exception handling to manage the cleanup?
> No, not really. From the place where we're calling into llvm we are catching all exceptions that may occur during compilation, but normally we do not add any additional catch clauses into the llvm source itself. We mainly rely on correct stack unwinding by destructors in llvm when an exception is thrown. In the cases when it is not sufficient, we had to add some additional autopointers, an in some cases implement additional unwind logic. In some cases we indeed had to add some exception handling in destructors in cases where they allocate memory, but such fixes are rather workarounds, because a correct solution would be to avoid memory allocation in destructors in the first place.
If I'm reading you correctly, you are relying on exception propagation 
and handler (destructors for local objects) execution. You have chosen 
not to add extra exception logic to LLVM itself, but are relying on the 
correctness of exception propagation within the code.  (The last two 
sentances are intended to be a restatement of what your message said.  
If I misunderstood, please correct me.)

Does this mean that you're compiling your build of LLVM with exceptions 
enabled?  By default, I believe LLVM is built without RTTI or exception 
support.

For the particular cases you mentioned with auto pointers and allocation 
in destructors, are these issues also present along existing error 
paths?  Or for that matter simply examples of bad coding practice?  If 
so, pushing back selected changes would be welcomed.  I'd be happy to 
help review.

Philip