Denis Koroskin wrote:
C standard library alloca function has an undefined behavior when requested size is large enough to cause a stack overflow, but many (good) implementations return null instead. So does DMD, for example. I believe it would be even better to go ahead and enforce D implementation to return a GC allocated chunk of memory instead of null in that case. It will not incur any performance hit in 99.9% of the cases and prevent a bug from being happen in the rest. It will also make writing code using it easier (and more safe), since you don't have to worry about possible stack overflow/null-dereference.
I'm a little reluctant to do this because alloca is supposed to be a low level routine, not one that has a dependency on the rather large and complex gc. A person using alloca is expecting stack allocation, and that it goes away after the function exits. Switching arbitrarily to the gc will not be detected and may hide a programming error (asking for a gigantic piece of memory is not anticipated for alloca, and could be caused by an overflow or logic error in calculating its size).
And secondly, I wish to emphasize that a null pointer seg fault is not an unsafe thing. It does not lead to memory corruption. It simply stops the program.
