Making alloca more safe

[Walter Bright]

Tomas Lindquist Olsen wrote:
> You spent quite a bit of effort explaining that segfaults never cause
> memory corruption, so it seems fairly reasonable to assume that some
> parts of the application state could still be valid and useful not to
> throw away.

When a seg fault occurs, it is because your program is in a state that 
you, the programmer, never anticipated. Therefore, you cannot know what 
state your data is in. Therefore, your data is unreliable. While it may 
not be in a bad state from memory corruption, it could very well be in a 
bad state from your program's logic being wrong.

Do you want to bet your life on assuming your program and its data is 
still valid?