[cxx-abi-dev] Run-time array checking

[Mike Herrick]

Getting back to the original proposals:

On Sep 6, 2012, at 8:46 AM, Mike Herrick wrote:

> 
> Here are some basic strategies for doing the run-time checking:
> 
> 1) Have the compiler generate inline code to do the bounds checking before calling the existing runtime routines.  The problem with this is that there is no IA-64 ABI standard way to throw a std::bad_array_new_length exception once a violation has been detected (so we'd need to add something like __cxa_throw_bad_array_new_length).
> 
> 2) Have the runtime libraries do the checking and throw std::bad_array_new_length as needed.  In order to do this (in a backwards compatible way) I think we'd need to add new versions of __cxa_vec_new2/__cxa_vec_new3 where the element_count is signed and the number of initializers in the array is passed as a new argument.
> 
> 3) A new routine, say __cxa_vec_new_check, that takes a signed element_count, element_size, and number of initialized elements and does all necessary checks, throwing std::bad_array_new_length if required, otherwise returning.  Compilers would insert a call to the new routine before any call to __cxa_vec_new* (when the number of elements isn't known at compile time).

It seems that option 2 is out (doesn't handle placement new[]), and option 3 has problems with signed/unsigned number of elements cases.  It appears that option 1 has had the most support (and gives the most flexibility).  Any objections (or other proposals)?

Mike.