[LLVMdev] optimization assumes malloc return is non-null

[John Regehr]

To say that LLVM *assumes* that malloc() succeeds or fails is misleading. 
This misstatement may be the root of people's ongoing problems in 
understanding this transformation and its validity.

The right way to think about it is: LLVM is supplying an alternate 
implementation of malloc that happens to run at compile time, and happens 
to succeed all the time.  This implementation is -- as I understand the C 
standard -- a perfectly legal one.  It has nothing to do with the version 
of malloc() found in libc except that the two implementations share a 
common API.

An implementation of malloc that always fails at compile time is legal 
too, but useless.

John Regehr